carb spacers and related intake modification

grumpyvette

Administrator
Staff member
I got asked this question ,

"I was wondering what one of these new Super Sucker carb spacers would bring compared to a regular 4 hole spacer."
Ill say right off that I have not used one of those super sucker spacers, personally, but I have seen several used, on cars and I have used very similar carb spacers many times,and worked on cars with them installed.
PB260008.jpg

spacerg1.jpg

carburetor spacers are used to either increase plenum volume or increase the distance from the carburetor venturies to the intake runner entrance's or too reduce the angle the airflow must make as it enters the intake runners from the plenum,or a combination of those factors.
the open center style are generally used on single plane, common plenum intakes while the four hole designs are generally used on the dual plane intake designs to try to increase the distance and lessen the angle from the carb base to the intake runner entrances below the carb,in an effort to smooth flow in the dual planes twin plenums without significantly reducing the low speed responsiveness

adding plenum volume tends to increase the upper rpm air flow rates and power , at the cost of a bit of low rpm crispness in throttle response, but that's not always true.while you can generally see the difference on a dyno test run, you may or may not be able to feel the difference from the drivers seat, but the use of a couple different spacers is almost always worth testing if you have the required hood to air cleaner clearance simply because gains of 5-15 hp are not UN-common when the proper spacer is used. yeah its amazing how often I get guys, in the shop with big plans,
who want to buy and install a new cam,or better heads etc.
and, you ask questions and you find they are clueless,
on how to correctly tune the current engine they have,
or there is obvious several badly mis-matched parts, that have been installed.
or currently badly adjusted or defective parts, and like you will frequently find,,
as a result, there is frequently a great deal of potential power found ,
in properly tuning most cars that the current owners leave on the table ,
simply because they don,t understand the current combos potential,
and think the only possible route to better power is installing new parts.



its almost always a good idea to blend the spacer edge to the intake plenum,to reduce potential turbulence,an edge might induce in the plenum, and in my experience its been rare for a 1" spacer on a single plane intake to give as much benefits as a 2" if you have the hood clearance id suggest testing the 2" version if you need more plenum volume, but since your increasing the plenum volume , if you add a spacer under the carb and changing the path of the air flow into the runners,you can be sure the carb jetting, power valves and /or accelerator pump or pump cam will need to be changed to compensate for that increased air in the plenum, to maintain the correct fuel/air ratio., so don,t just slap on the spacer and expect its operating at its true potential, its almost sure to require some re-tuning to maximize its efficiency.
If your curious if a divided spacer vs a common one open plenum spacer is the best choice on your particular engine the answer to that question correctly I'd point out that the,
"spacer design you select, its height and volume has an effect on how the change the spacer provides to the original intakes plenum air flow will effect the engines performance"
what a spacer does is add both distance from the carbs base to the plenum floor and extra volume to the area of the intake manifolds plenum(s) (in the case of a dual plane split plenum) adding distance and volume tends to allow a smoother more gradual change in direction to the air flow volume, this tends to allow higher engine air flow to effectively enter the individual intake runner passages thus potentially raising engine rpm.
on a dual plane intake keeping the two sides isolated tends to keep the low and mid rpm throttle response crisp, at the cost of a small amount of potential flow increase that a common open spacer would allow. keeping the two plenums separate on a dual plane intake manifold plenum,will in theory retain the low and mid rpm throttle response and the spacer added volume may add some extra rpm potential, use of an open common plenum spacer should gain more peak power at the cost of some lower rpm crispness especially at part throttle acceleration , but you may need a dyno to see the difference as changes of 5-7 hp are common all though larger changes are not at all rare
fuel droplets tend to stay suspended in the air flow best when there's few abrupt changes in direction, (one reason the dual carb tunnel ram intakes tend to perform very well in the higher rpm ranges)
intakew-tunnel.jpg

trampic7.jpg

simply because its nearly a strait line from carb base to inlet valve in the engine.
while the open common spacer may gain you a bit more rpm, it tends to cost you a bit of off idle and low speed responsiveness, but the displacement, cam timing, compression, exhaust scavenging and intake design all effect results so realistically testing is the only way to find out for sure!

1102sp.jpg


This is a pipemax output for a 500 cuin 1400hp pro stock engine.

Minimum Plenum Volume CC = 1805.5 [typically for Single-Plane Intakes]
Minimum Plenum Volume CID= 110.2 [typically for Single-Plane Intakes]
Maximum Plenum Volume CC = 8188.0 [typically for Tunnel Ram Intakes]
Maximum Plenum Volume CID= 499.7 [typically for Tunnel Ram Intakes]


This one is for a 362 cuin SBC Super Stock.

Minimum Plenum Volume CC = 998.5 [typically for Single-Plane Intakes]
Minimum Plenum Volume CID= 60.9 [typically for Single-Plane Intakes]
Maximum Plenum Volume CC = 5942.9 [typically for Tunnel Ram Intakes]
Maximum Plenum Volume CID= 362.7 [typically for Tunnel Ram Intakes]

http://garage.grumpysperformance.com/index.php?threads/carb-intake-test.58/

http://garage.grumpysperformance.com/index.php?threads/modifying-a-phenolic-carb-spacer.12342/


look closely, at the super sucker spacers, they are NOT a true 4 hole design,like this
edl-8711_m.jpg

spacers on DUAL PLANE intakes usually have 4 individual holes feeding from the carb venturies or throttle bores, the dual plane intake design is meant to limit each group of cylinders plenum volume to maintain high air flow speeds that help lower rpm torque and hold fuel droplets in suspension, OPEN spacers are generally used on single plane intakes designs with a common plenum feeding all intake runners, this allows each intake runner to draw from 4 vs two throttle bores thus effectively allowing a carb rated at a certain value IE 750 CFM or 850 CFM to more efficiently feed all the intake runners, from the common plenum, but this reduces lower rpm air flow speeds


EDL-7501_sSN.jpg

dualp.png


hly-300-110.jpg

singlep.png

0210hpp_flow04.jpg

carter.jpg

carter1.jpg

carter1f.jpg

be aware that the holley carbs generally take the larger bolt pattern compared to the early carter carbs like those used on the 1957 vette with dual quads, (RED HOLES)and many carter carbs have a dual bolt pattern
carter2.jpg



that maintains isolated plenum feed from each side of the carb.
they are a MODIFIED open plenum design, like this
that will have a similar effect to this
edl-8725_m.jpg

in that the dual plenums are linked under the spacer,they appear to be designed to add plenum volume to a single plane intakes plenum, and smooth the air flow transition from carb to plenum, so that will have a similar effect to this[/b]
edl-8710_m.jpg

they seem to have an anti reversion design to limit reverse flow from the plenum which can be useful.

phenolic spacers work well just don,t get the cheap plastic knock off versions that warp and leak, and be aware that the dual plane intakes tend to work best with the 1"and 2" four hole designs but single planes tend to work best with the larger single open plenum designs

sum-g1404.jpg

http://www.summitracing.com/parts/SUM-G1404/

edl-8714.jpg


http://store.summitracing.com/parts/edl ... dia/images
extended divider carb spacer

HEAT BARRIER TYPE SPACER
if your having heat issues like carbs with fuel boiling from engine heat in the intake,a aluminum and gasket heat barrier plus, like the one below with a 1" phenolic spacer placed above it will usually reduce heat transfer rates significantly, as the heats transferred to the engine compartment air before it can get thru the layered barriers
720-3710.jpg


http://www.jegs.com/i/Mr-Gasket/720/371 ... tId=743789

I prefer the standard spacer designs,but in some applications you might see gains from that anti reversion lower spacer design.
many of the newer guys will not have done that spacer swap, and its a tuning aid, that can help some applications
Ill also add that if you have the room under the hood, adding a second phenolic 4-hole 1/2" tall carb insulator or swapping to a 1" or even a 2"phenolic 4-hole spacer may further improve the carb cooling and may help the fuel atomization slightly, but the correct spacer must be matched to the style of intake manifold.
increasing plenum volume in the intake with a spacer tends to make the engine run as if the carburetor your using is slightly larger than it will without the spacer,generally reducing the upper rpm powers curve and slightly reducing the low rpm torque , but each application will have slightly different trade offs, sometimes the gains far out weight the losses
the object is to increase the plenum volume and effectively reduce the abrupt angle change the airflow leaving the carburetor venturies must make to enter the intake runners, because reducing the abrupt angle change tends to reduce fuel, droplets from falling out of the intake runner air flow and puddling in the plenum floor area


350871213.jpg

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=708&prmenbr=361
even back in the early 1960s they were well aware that long intake runners on race engines provided a significant inertial ram tuning benefit that increased mid range torque
ramtunein.jpg

look closely at the carb base mount area
READ LINKS
http://www.superchevy.com/how-to/additional-tech/0906chp-carburetor-spacer-buyers-guide/

http://www.badasscars.com/index.cfm...ct_id=425/category_id=13/mode=prod/prd425.htm

http://www.hotrod.com/how-to/engine/0601phr-best-carb-spacers-cheap-horsepower/


http://garage.grumpysperformance.co...ads-tuned-intake-turbulence.12998/#post-67611

http://www.summitracing.com/expertadviceandnews/professoroverdrive/answer/485

http://www.jomarperformance.com/spacers.php


http://garage.grumpysperformance.com/index.php?threads/modifying-a-phenolic-carb-spacer.12342/
 
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grumpyvette

Administrator
Staff member
Re: carb spacers

having the plenum divider fully in place below the carb base, tends to help lower rpm torque and crisp responsiveness to minor throttle position changes, removing the divider effectively increases the plenum volume the runners draw from and that tends to slow low rpm response to throttle changes but it tends of increase the flow rates slightly at high rpms so power in the upper rpm band tends to go up as the plenum volume is less of a restriction.
notching the divider tends to split the difference to some extent.
theres two basic carb spacer designs, they are commonly 1" or 2" tall, the one hole open spacer and the 4 hole designs, the 4 hole design in effect maintains the divided plenum, but adds plenum volume and reduces the restriction the limited space between the carbs venturies and individual intake runner entrances can have in some intake designs.
the open common plenum spacers are designed for use with single plane intakes where adding plenum volume helps upper rpm flow..
naturally you can mix/match and gain or loose plenum volume, and increase the distance from the carb base to the intake runners entrance, which can be helpful, especially if your installing a nitrous plate under the carb, or if your intake currently lacks plenum volume for your application.If you have the hood clearance ,before doing any mods to a dual plane intakes plenum divider you should try adding and testing your combo separately with (BOTH) a 1"-0r 2" open center and 4 hole carb spacers under the carbs, as it will give a clearer indication of how your engine will respond to changes in the plenum design, and if it gets WORSE its a fair indicator that removing the current plenum divider will not help much, generally removing the current plenum divider will kill some low rpm torque and increase the peak hp but thats NOT always a good trade off,in your cars E.T./1/4 mile time slip
as a general guide,and assuming your static compression ratio matches the cam duration you select, if your running less than about a 235 dur @ .050 lift cam, with a 2.57:1-3.36:1rear gear ratio, a dual plane intake should prove beneficial, have more than about 245 degrees dur. @ .050 lift, and a 3.45:1-plus rear gear and a single plane intake will generally prove useful.
its common for the four hole design spacers to work better on the dual plane intakes and the open plenums to work better on the single plane intakes but your combo will require testing as there are exceptions.
btw if your adding a NITROUS spray bar plate under the carb,and have the necessary hood clearance required, adding an open plenum spacer, under the NITROUS spray bar plate, that's effectively adding some volume & distance to the plenum and runner entrances and allowing more room for the fuel/air mix to blend usually helps the fuel/air/nitrous distribution consistency between cylinders
you might find reading thru this info below of interest

http://www.vintagemusclecarparts.com/pa ... 6pg10.html

http://www.highperformancepontiac.com/t ... index.html

http://victorylibrary.com/mopar/intake-tech.htm

http://www.not2fast.com/gasflow/Lecture ... cument.htm

http://www.jagweb.com/aj6eng/technics.html

http://books.google.com/books?id=AatRNA ... q=&f=false

http://www.racingheadservice.com/rhs/in ... -chevyhtml

http://www.phys.unsw.edu.au/jw/Helmholtz.html

http://www.cartechbooks.com/cartech/con ... es/194.pdf

in an ideal world you generally start with a plenum volume of about 1/2 the engines displacement and work up to about 3/4 of the engines displacement, as in most case thats the range that will provide the best hp, but cam duration, lsa,intake runner length and cross sectional area ,cam lift, exhaust scavenging, tuning the exhaust, will all effect your results,and the intake design effects the requirements, a tunnel ram will be a different deal than a low rise single plain design, if you really want to research it, one fairly safe rule of thumb is that if your cam has less than about 235-240 duration @.050 lift, a DUAL plane like a edelbrock air gap with a full intact divider under the carb, will provide the best results.
you can,t compare EFI that's fogging fuel directly into the cylinder head ports, and air speed is far less of an issue, to a carb that's designed for routing fuel/air mix thru runners, and requires higher port air speedsread thru this linked info and ALL THE SUB LINKS

viewtopic.php?f=55&t=858

viewtopic.php?f=52&t=796

viewtopic.php?f=56&t=1730

even a new guy should easily get an additional 10-15 hp out of a minimal port and bowl area clean-up procedure after reading these threads & links, and 20 plus hp is not that hard to do, on many engines


http://garage.grumpysperformance.co...-by-step-guide-with-pictures.5378/#post-56651

http://garage.grumpysperformance.com/index.php?threads/porting-can-help.462/page-3#post-59145

http://garage.grumpysperformance.co...olishing-combustion-chambers.2630/#post-50247

http://garage.grumpysperformance.co...ed-intake-modification.1038/page-2#post-49827

http://garage.grumpysperformance.co...ing-tools-abrasives-sources.10683/#post-46209

http://garage.grumpysperformance.co...o-experience-read-this-long.10145/#post-39861

http://garage.grumpysperformance.com/index.php?threads/shop-vacuum-cleaner.3379/#post-8946

http://garage.grumpysperformance.co...ort-gasket-matching-an-intake.2773/#post-7802

http://garage.grumpysperformance.com/index.php?threads/air-die-grinders.1831/#post-4763

http://garage.grumpysperformance.com/index.php?threads/compressor-info.24/
 
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grumpyvette

Administrator
Staff member
Re: carb spacers

now Id point out that spacers under the 4 hole throttle body, or a carb on some intake plenums , also can be used on the single plane MPFI INTAKES to add extra plenum volume and smooth out the air flow transfer or reduce the abrupt change in direction the air flow must make as it enters the individual intake runners, from the lower throttle body or carb venturies, to the intake runner entrances, in some cases aluminum spacers are epoxied or TIG welded to a plenum to provide the necessary material to allow room and the distance for extra porting work to blend the transition from the carb venturies to the runner entrances

bro-hvss4500cla_w.jpg

btw its upside down in this picture
hly-9901-101-1.jpg

hly-9900-171.jpg


but remember ,factors like the plenum volume, exhaust tuning or exhaust flow restriction, engine compression ratio, drive train gearing and cam timing and average rpm band used, will all effect the results, generally when I test those spacers they help slightly but NOT in ALL cases, once you get it tuned without one, you can, and should try one to see if it helps but its rare to see more than minor changes
 

grumpyvette

Administrator
Staff member
ctrp_1102_01+engine_myths.jpg

while a rather common modification to a dual plane intake manifold is done by removing an inch of the divider wall in the plenum, under the carbs base ,
cutplenumdivider.jpg

as this will generally result in a bit more upper rpm air flow, and peak power numbers, and as a result it can provide the engine a bit more, peak rpm power as a result,

(yes even some factory intake designs have the plenum divider wall notched)
7161v.jpg

its generally a better option too simply install an open 1" or even a 2" spacer under the carburetor if the hood clearance allows you too do so,to test out this option,on your application,this added plenum volume and added height tends to increase air flow rates a bit more effectively and reduce plenum turbulence, and less fuel tends to drop out of the air flow, thus you retain marginally better fuel distribution between cylinders,
https://www.summitracing.com/parts/...MI-tKEpZrN1wIVRLbACh2wywdGEAQYBSABEgJUnPD_BwE
opencarbsp.jpg

as its a far easier to reverse modification if you find you don,t like the new slightly lower throttle response,
off idle ,crispness that also commonly results from the more open plenum design.

the mod effectively reduces the dual plane to a badly designed single plane intake, it might still make decent power, but its not generally as effective as a true single plane design in the upper rpm range and it tends to have sacrificed some low rpm power also, the partial divider removal above can at times help smooth out, and slightly increase, the cars low speed power curve, but generally theres a slight loss in low rpm crisp response , so just a bit of open discussion here, I know many of you have done that cutting down the dual plenum divider mod and I own a milling machine and have done it for several friends in the past and ,yes you generally do pick up some peak horsepower as a result of the increase in plenum flow rates in the upper rpm band.
yet I will point out what your basically doing is converting a dual plane intake into what is in effect a rather poorly designed single plane intake design. the stepped plenum generally requires staggered carburetor jetting and other tweaks to tune correctly, if your contemplating cutting the divider wall, Id suggest a temporary test by installing a 2" open center carb spacer ,as the additional open area will effectively provide most or all of the potential benefits that removing the divider plenum wall may.(yes I know hood clearance issues may be a factor, preventing this)

carbsp.png


dualp.png


singlep.png



int2bv.jpg


12cal.jpg

qjetve.png

FEL-17845_ml.jpg

place the spacer in a vise on the mill, or drill press, accurately index the hole saw

g7946_det1.jpg


line up the carb ,mounting bolt holes, spray the spacer with bright red paint and use a properly sized hole saw ,on a mill or drill press to open the rear section venturies and a die grinder to contour the remainder
Z19Osa.jpg


12256.jpg

NS10033.jpg



Carburetor Spacers
You've likely read or heard about an assortment of consequences when a carburetor is raised (or lowered) relative to an intake manifold's plenum floor. More plenum volume helps high rpm, for example. Or maybe, smaller carburetors like more spacer. This isn't to say these analogies are incorrect, but maybe the reasons are a bit obscure.

For example, let's look at it this way. A carburetor is a pressure differential device. It delivers fuel into a region that's designed to be at less than atmospheric pressure. It's a fuel metering "signal" that allows atmospheric pressure to force fuel into the incoming airstream, acting through the carburetor's bowl vents. By elevating a carburetor, all else being equal, it becomes more remote to runner entries and thus can experience a weaker metering signal. The carburetor tends to act "leaner" in the presence of a decreased signal. Aggregate airflow tends to be the same but there's less fuel flow, so fuel enrichment is decreased.

However, as Smokey often said, "there's one more little item." Once discharged from the carburetor, air/fuel charges are required to make a relatively abrupt turn into the manifold's runners. Air, being compressible can navigate this sudden change more easily than fuel. Increasing carburetor height allows air/fuel charges more time to slow down and make the turn more effectively, often reducing the possibility of air and fuel separation. As carburetor size is decreased and no spacer is used, the problem becomes more critical. In fact, carburetors placed too near a plenum floor can be akin to sticking a hose in a bucket with fuel impingement materially upsetting proper air/fuel mixtures.

One key here is to map brake specific fuel consumption (BSFC) data as carburetor height is changed, assuming carburetor sizing remains the same. If a disproportionate amount of fuel is required for best power and BSFC data are trending higher and higher, chances are good mixture quality is being upset and raising the carburetor is a potential solution.

On the other hand, if you discover that a four-hole spacer is beneficial, possible reasons include the fact the fuel metering signals were insufficient (for the calibration or jetting being used) and stronger signals provided by the spacer helped deliver additional fuel. But in virtually any case, power changes from raising or lowering a carburetor affect more areas than plenum volume.




BTW, while were discussing intake manifold modifications lets spend 2 seconds on what may be the most over-looked and one potentially important area, the runner entrances.
I can,t tell you how many times I see guys take intakes out of the box and just bolt them on, and then expect the thing to perform up to its full potential....which its NEVER going to do with out some basic clean-up. de-burr, and contour work being done because the as cast surfaces are rarely smooth or correctly contoured, its not going to give you an extra 50 hp , but it can result in 5-10-even on occasion 20hp over a significant part of your engines primary power band


heres a couple professionally re-worked single plane intake plenums, notice they don,t look a lot like the out of the box plenumsthe port entrance is raised and smoother the dividers are contoured, etc.
plenum1.jpg


plenum2.jpg

plenum3.jpg

plenum4.jpg

plenum5.JPG


plenum7.jpg

heres a small tip you gain from experience, if your running a dual plane intake its got two different plenums and its not really uncommon for a carb to require the jets to be different sizes especially on the primary side of the carburetor because of the markedly different plenum volume and distance to the intake runner entrances.
look at this picture, notice the LOWER red plenum and UPPER blue plenum sections and related cylinder numbers
ede7501-manifold.jpg


youll notice the dual plane intake is really two distinct intakes , effectively separating the carburetor into two separate 4 cylinder configurations.
its not uncommon to find one batch or side of the intake running lean or rich, and it helps to understand that because at times youll find problems getting the engine tune correct that show indications that relate to only one plenum, but less experienced tuners fail to catch this early because its not related to only one side of the engine!
this is what you currently have :shock:
3569663093_a3154daf45.jpg


This is what you want to have (you can almost see the HP) :twisted:
3570475166_573ac383e5.jpg

porting helps flow significantly

if the port exit on the intake is a bit smaller than the port entrance on the heads its not nearly as beneficial to port match the intake/cylinder head interface as it will be if the mis-match is a larger intake exit to head port, if the ports are off set the sides that mis-align follow the same basic concept, a slight lip or step should be removed and blended smoothly if it forms a restriction to flow in the direction the ports designed to flow, but your potential gains from port work are small as the height is less than about 1/16"
slight steps that resist flow in the wrong direction, like when the head ports are larger than the intake runner exits, tend to help limit reversion pulse strength in the plenum , but I try to be reasonable and keep even those mis-match steps less than 3/32" max and blending those may prove more beneficial in some cases. just remember to blend any changes in dimensions for at least 1" into the runners or ports


don,t forget the runner entrances in the plenum also need clean-up

heres some intake plenum port clean-up done by Dr. J's Performance

carbplenum.jpg


carbplenum1.jpg


read these threads and sub links

viewtopic.php?f=55&t=2773&p=7200&hilit=gasket+porting+intake#p7200

viewtopic.php?f=52&t=462&p=7593&hilit=gasket+porting+intake#p7593

http://www.circletrack.com/techarticles ... index.html

BTW everyone eventually screws up some part made of aluminum, and TIG welding and re machining will fix almost any aluminum part, especially cylinder heads where heat and pressure make using epoxy less than ideal in many cases, but for minor intake manifold runner, and plenum repairs you usually have a second option, with welding you take a chance of warping the intake casting, but with a paste made from two part epoxy, 75% epoxy and 25% aluminum powder mix, the mix makes a very durable port wall filler paste,vaguely resembling a silver bondo paste but far more durable..
this paste is very useful when correcting intake runner porting mistakes as the paste once cured is machinable to some extent almost like the original aluminum, just be very sure the surface you use the epoxy on is very clean and a thin wet bond coat of epoxy gel a few thousands thick used just before using the paste on the surface before applying the aluminum mixed epoxy filler helps bond the mixed paste


http://www.ramracing.us/products.htm

http://www.jamestowndistributors.com/us ... 8&type=pla

READ THE LINKED INFO
http://www.maximumraceengines.com/intak ... rting.html

viewtopic.php?f=52&t=333&p=8319&hilit=porting+help#p8319

viewtopic.php?f=52&t=462&st=0&sk=t&sd=a&hilit=porting+help

http://www.j-performance.com/index.php? ... &Itemid=42

http://www.hotrod.com/techarticles/engi ... index.html

viewtopic.php?f=55&t=2773&p=7200&hilit=+port+match#p7200

viewtopic.php?f=55&t=10310

many guys spend 90% of there porting time on intakes matching the ports to the heads and opening the runners up, but a surprising amount of the potential flow improvement on many intakes involves the port work on the runner entrances in the plenum area.
plen1.JPG

plen2.JPG

plen3.JPG

plen4.JPG

plen5.JPG

plen6.JPG
 
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grumpyvette

Administrator
Staff member
AS usual, reading the links provides you with a good deal more info :mrgreen:
http://www.circletrack.com/enginetech/c ... index.html

http://www.hotrod.com/techarticles/carb ... index.html

http://www.automedia.com/Carburetor_Spa ... 080701cs/1

http://www.corvettefever.com/techarticl ... index.html

http://www.popularhotrodding.com/buyers ... index.html

http://marineperformancetechtalk.com/carb_spacers.htm

http://www.motorsportsvillage.com/carbu ... acers.html


turtle spacer 1.png

you can fabricate or in some cases modify intake plenums or add on spacers with plenum dividers, or "TURTLES" to get the air flow characteristics you desire
turtle spacer 2.png

turtle spacer 3.jpg



spacers can be used on either dual plane or single plane intakes but generally youll find increased plenum volume and lowering the angle change into the intake runners tends to benefit the mid or upper rpm power and can reduce the low rpm, or off idle throttle response, but thats not always true, as in some cases the change has little effect or does amazing things, Ive seen 12-15 hp gains on some big block single plane intakes with 2" spacers, ID also point out that changes in cams or cam timing changes and tuning the headers collector length can frequently make a noticeable difference in the spacers effectiveness in some cases

sum-g1404.jpg

http://www.summitracing.com/parts/SUM-G1404/

HEAT BARRIER TYPE SPACER

355CI SMALL-BLOCK CHEVY
NO SPACER VERSUS SPACER
RPM TQ1 TQ2 HP1 HP2 TQ DIFF. HP DIFF.
2,500 340.7 322.2 162.2 153.4 -18.5 -8.8
3,000 352.6 347.6 201.4 198.6 -5 -2.8
3,500 377.1 371.9 251.3 247.8 -5.2 -3.5
4,000 420.7 422.4 320.4 321.7 1.7 1.3
4,500 459.7 464.3 393.9 397.8 4.6 3.9
5,000 462 466.5 439.8 444.1 4.5 4.3
5,500 457.2 464.3 478.8 486.2 7.1 7.4
6,000 443.7 448.2 506.9 512 4.5 5.1
6,500 423.1 427.9 523.6 529.6 4.8 6
7,000 380.4 392.7 507 523.4 12.3 16.4
7,500 305.8 318 436.7 454.1 12.2 17.4
wcarburetorspacers1.jpg

wcarburetorspacers2.jpg

wcarburetorspacers3.jpg
 
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grumpyvette

Administrator
Staff member
http://www.j-performance.com/index.php? ... &Itemid=42

http://www.hotrod.com/techarticles/engi ... index.html

http://www.compfuelsystems.com/airflow.html

heres some rather interesting porting data on some intakes

Dr J's Performance Ported Chevy Intake Manifolds PDF Print E-mail


Edelbrock Super Victor 4500 BBC
Tall Deck Part # 2916
dj1.jpg


intake_manifold_data_base_ported_super_victor_4500_big_block_chevy_tall_deck

As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 430 1) 516 + 86 cfm
3) 432 3) 534 +102 cfm
5) 398 5) 511 +113 cfm
7) 426 7) 504 + 78 cfm

2) 425 2) 517 + 92 cfm
4) 400 4) 505 +105 cfm
6) 419 6) 531 +112 cfm
8) 435 8) 519 + 84 cfm

* Gasket matched to AFR #6856
* intake flow test at 28 inches


Professional Products BBC Hurricane
part # 53031

professional products 53031
dj2.jpg







As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 392 1) 426 + 34 cfm
3) 375 3) 451 + 76 cfm
5) 381 5) 426 + 45 cfm
7) 379 7) 475 + 96 cfm

2) 376 2) 471 + 95 cfm
4) 378 4) 428 + 50 cfm
6) 375 6) 450 + 75 cfm
8) 388 8) 432 + 44 cfm

* Gasket matched to ROL # NI-2085
* intake flow test at 28 inches

dj3.jpg

Edelbrock Performer 2-0 BBC Oval Port

edelbrock performer bbc 2-0



As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 310 1) 321 + 11 cfm
3) 304 3) 323 + 19 cfm
5) 297 5) 324 + 27 cfm
7) 312 7) 343 + 31 cfm

2) 310 2) 315 + 5 cfm
4) 299 4) 338 + 39 cfm
6) 297 6) 243 + 54 cfm
8) 305 8) 317 + 12 cfm

* Gasket matched to Felpro 1212
* intake flow test at 28 inches


Edelbrock Super Victor SBC part #2925
dj4.jpg

intake_manifold_database_ported_super_victor_sbc

As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 300 1) 347 + 47 cfm
3) 276 3) 341 + 64 cfm
5) 276 5) 352 + 76 cfm
7) 288 7) 355 + 67 cfm

2) 292 2) 351 + 59 cfm
4) 271 4) 357 + 86 cfm
6) 276 6) 341 + 70 cfm
8) 294 8) 346 + 52 cfm

* Gasket matched to Felpro 1206
* intake flow test at 28 inches

Edelbrock Super Victor SBC part #2926
dj5.jpg

ported_edelbrock_2926_super_victor_small_block_chevy_sbc

As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 299 1) 345 + 46 cfm
3) 274 3) 339 + 65 cfm
5) 273 5) 341 + 68 cfm
7) 282 7) 345 + 63 cfm

2) 294 2) 348 + 54 cfm
4) 274 4) 341 + 67 cfm
6) 276 6) 340 + 65 cfm
8) 291 8) 347 + 56 cfm

* Gasket matched to Felpro 1263
* intake flow test at 28 inches

Edelbrock Victor Jr. SBC part # 2975
dj6.jpg

intake_manifold_database_ported_edebrock_victor_jr_sbc

As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 252 1) 302 + 50 cfm
3) 248 3) 296 + 48 cfm
5) 239 5) 304 + 65 cfm
7) 251 7) 308 + 57 cfm

2) 256 2) 316 + 60 cfm
4) 246 4) 298 + 50 cfm
6) 237 6) 306 + 69 cfm
8) 250 8) 302 + 52 cfm

* Gasket matched to Felpro 1206
* intake flow test at 28 inches


World Motown Single Plane SBC 4150 # 061040
dj7.jpg

world motown sbc 4150



As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 317 1) 343 + 26 cfm
3) 255 3) 340 + 85 cfm
5) 295 5) 337 + 58 cfm
7) 301 7) 346 + 45 cfm

2) 312 2) 355 + 43 cfm
4) 281 4) 337 + 56 cfm
6) 260 6) 338 + 78 cfm
8) 304 8) 355 + 51 cfm

* Gasket matched to Felpro 1206
* intake flow test at 28 inches



Holly Strip Dominator part # 300-25
dj8.jpg

holley strip dominator 300-25




As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 293 1) 318 + 25 cfm
3) 288 3) 316 + 28 cfm
5) 291 5) 330 + 39 cfm
7) 310 7) 336 + 26 cfm

2) 301 2) 336 + 35 cfm
4) 283 4) 318 + 35 cfm
6) 285 6) 314 + 29 cfm
8) 304 8) 324 + 20 cfm

* Gasket matched to Felpro 1206
* intake flow test at 28 inches


Edelbrock Performer RPM Air Gap SBC part # 7501

dj9.jpg

chevy rpm_air_gap


As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 214 1) 288 + 74 cfm
3) 224 3) 308 + 84 cfm
5) 221 5) 312 + 91 cfm
7) 208 7) 282 + 74 cfm

2) 218 2) 304 + 86 cfm
4) 213 4) 288 + 75 cfm
6) 210 6) 286 + 76 cfm
8) 220 8) 306 + 86 cfm

* Gasket matched to Felpro 1206
* intake flow test at 28 inches


Edelbrock Performer RPM Air Gap SBC part # 7501

dj10.jpg

intake_manifold_database_ported_edelbrock_performer_rpm_air_gap_sbc

As Cast Dr J's Ported
(runners cfm) (runners cfm)
CFM Gains
1) 214 1) 284 + 70 cfm
3) 224 3) 288 + 64 cfm
5) 221 5) 297 + 76 cfm
7) 208 7) 293 + 85 cfm

2) 218 2) 290 + 72 cfm
4) 213 4) 288 + 75 cfm
6) 210 6) 287 + 77 cfm
8) 220 8) 293 + 73 cfm

* Gasket matched to Felpro 1205
* intake flow test at 28 inches

just a bit of info on intake gaskets sizes to match port cross sectional areas

portcsa.jpg


COMMON SBC INTAKE PORTS
felpro # 1204=Port Size: 1.23" x 1.99"

felpro # 1205=Port Size: 1.28" x 2.09"

felpro # 1206=Port Size: 1.34" x 2.21"

felpro # 1207=Port Size: 1.38" x 2.28"

felpro # 1209=Port Size: 1.38" x 2.38"

felpro # 1255 VORTEC=Port Size: 1.08" x 2.16"

felpro # 1263=Port Size: 1.31" x 2.02"

felpro # 1266=Port Size: 1.34" x 2.21"

felpro # 1284 LT1=Port Size: 1.25 x 2.04''

felpro # 1289 FASTBURN=Port Size: 1.30" x 2.31"

Felpro-Gasket-Port-Sizes.jpg



related info




viewtopic.php?f=27&t=408&p=13626&hilit=flow+bench#p13626

viewtopic.php?f=52&t=2630&p=13145&hilit=port+match#p13145

viewtopic.php?f=52&t=4664&p=12600&hilit=port+match#p12600

viewtopic.php?f=52&t=462&p=11902&hilit=port+match#p11902

viewtopic.php?f=55&t=4362&p=11826&hilit=port+match#p11826

viewtopic.php?f=55&t=624&p=11495&hilit=port+match#p11495

viewtopic.php?f=52&t=322&p=10973&hilit=port+match#p10973


viewtopic.php?f=56&t=495&p=14243&hilit=header+scavenging#p14243

viewtopic.php?f=53&t=3893&p=10304&hilit=header+scavenging#p10304

viewtopic.php?f=52&t=1070&p=9919&hilit=header+scavenging#p9919

viewtopic.php?f=56&t=1503&p=8318&hilit=header+scavenging#p8318

viewtopic.php?f=56&t=1730&p=5392&hilit=header+scavenging#p5392
 

Randy_W

reliable source of info
To add one thing to this great piece, and not really about spacers per se, but;
If you put an Edelbrock square bore carb on a spreadbore intake DO NOT use an open single hole adapter! It will cause driveability issues often times and hurt idle quality, off idle response, torque and mpg. Only the 4 hole adapter/spacers design specifically for this swap should be used on a street driven car.
Use this;
350-2697.jpg


Not this;
350-2693.jpg
 

grumpyvette

Administrator
Staff member
OK guys, here is the scoop. I've been working with Chris Cobb at DynoTune Engineering, www.dynotuneengineering.com in Paris Tennessee. First, one nice guy! Anyone who needs dyno service, fabrication, engine assembly, needs to check him out!!

To make this a fair test, the manifolds and engine were tuned to a 13.2 AFR.

The engine that was used as a test mule is a UMP Dirt Modified. Here is the breakdown.

414 cid
3.875/4.125
6.0 rod
13.02 compression
Dart Pro 1 227cc CNC heads
264/270 106 LSA installed at 103
.670/.679 lift
1.750 headers
12" long collectors
35º timing
4150 gas 950 Ultra HP

The dyno session was to compare a box stock 2925 vs a Modified Plenum 2925. Other manifolds were tested, we will get to them.

Results:

STOCK 2925:
594.4 hp at 6300 rpm
564.6 tq at 4700 rpm
Average: 560.3/505.5

MODIFIED 2925:
616.9 hp at 6600 rpm
571.9 tq at 4900 rpm
Average: 580.0/522.6

Note: Chris said it accelerated .10 faster than the stock manifold! I'll have more info as we go. He is testing spacers tonight..

DynoTune Engineering
3745 HWY 79 S
Paris, Tennessee 38242
731-336-6899

Here are the comparisons for the Edelbrock Super Victor 2925 vs the Motown 061040. Both intakes were right out of box with no work done. The Motown was slightly better in each of these test, but it showed the biggest improvement in the test with no carb spacers. Another area that it showed improvement was the elasped time of the pull and the increase in average acceleration rate during the pull.

DynoTune Engineering - SBC Dirt Modified 414 - Intake Manifold Dyno Test


No Spacer Edelbrock 2925 Non-Ported No Spacer Motown 061040 Non Ported

Peak Torque 557 >>>> 570 Difference = 13
Peak Hp 586 >>>> 595 Difference = 9
Avg Torque 499 >>>> 506 Difference = 7
Avg Hp 553 >>>> 561 Difference = 8

1" Open Spacer Edelbrock 2925 Non-Ported 1" Open Spacer Motown 061040 Non Ported

Peak Torque 562 >>>> 568 Difference = 6
Peak Hp 594 >>>> 597 Difference = 3
Avg Torque 505 >>>> 508 Difference = 3
Avg Hp 559 >>>> 563 Difference = 4

1" Super Sucker Edelbrock 2925 Non-Ported 1" Super Sucker Motown 061040 Non Ported

Peak Torque 561 >>>> 566 Difference = 5
Peak Hp 593 >>>> 597 Difference = 4
Avg Torque 503 >>>> 507 Difference = 4
Avg Hp 557 >>>> 562 Difference = 5

2" Super Sucker Edelbrock 2925 Non-Ported 2" Super Sucker Motown 061040 Non Ported

Peak Torque 565 >>>> 565 Difference = 0
Peak Hp 594 >>>> 598 Difference = 4
Avg Torque 506 >>>> 509 Difference = 3
Avg Hp 560 >>>> 564 Difference = 4

These test were performed back to back within a couple of hours of each other on the same day. We have other manifolds that were tested in this test and will share those results later.

Thanks,

_________________
Chris Cobb
 

Todd_W_White

New Member
Hello folks!

I appreciate this thread very much! I've read it, and most of the links, too, and would like to ask the following:

I'm running a 1965 Chevrolet 283, recently rebuilt, with an RV cam in (this is in my Chevy C-10). My intake is an Edelbrock, but I'm not sure which one, but it's aluminum and has the split plenum divider for a 4-bbl carb. My carb was chosen for fuel economy and mild performance (mostly economy), and is a fully rebuilt Holley 4360 Economaster, which is a spreadbore type carb. My current in-town mileage averages 17 mpg, so I'm happy with that, but not with the problem I'm having now that summer is here.

Here in NE Oklahoma, we have high humidity most of the year, and the temperature in summer is often at or above 100-degrees. This puts the heat index at or above 110-degrees many days. My truck has been running wonderfully since I got her going this past Spring, but, when the summer heat hit, I started having problems with vaporlocking. I replaced the fuel pump (mechanical), and re-routed the fuel line, but to no avail. I've traced it down to the high probability that the aluminum manifold is transferring the engine heat so well to the carb that the fuel is vaprozing in the bowl.

I understand that a phenolic spacer is the typical choice to solve this problem. Typical aftermarket spacers of this type fit the Holley spreadbore, but the hole sizes aren't correct for my carb. The Primaries on my 4360 are 1-3/8" in diameter, and the Secondaries are 1-7/16" in diameter. The holes in the phenolic spacers are made for the typical Holley 4-bbl carb, and, thus, are not direct matches for the openings in my carburetor.

That said, here are my questions:

1. Should I be looking for the open style or hole type phenolic spacer?

2. How thick should I get?

3. Will the difference in hole diameters affect the proper performance of my carburetor and engine?

4. Will adding a spacer affect the performance of my 4360/283 combination, and, if so, in what way?

5. Will adding the spacer require a change in my jets?

Thank you all in advance for your help!

- Todd W. White
 

grumpyvette

Administrator
Staff member
Todd_W_White said:
Hello folks!

I appreciate this thread very much! I've read it, and most of the links, too, and would like to ask the following:

I'm running a 1965 Chevrolet 283, recently rebuilt, with an RV cam in (this is in my Chevy C-10). My intake is an Edelbrock, but I'm not sure which one, but it's aluminum and has the split plenum divider for a 4-bbl carb. My carb was chosen for fuel economy and mild performance (mostly economy), and is a fully rebuilt Holley 4360 Economaster, which is a spreadbore type carb. My current in-town mileage averages 17 mpg, so I'm happy with that, but not with the problem I'm having now that summer is here.

Here in NE Oklahoma, we have high humidity most of the year, and the temperature in summer is often at or above 100-degrees. This puts the heat index at or above 110-degrees many days. My truck has been running wonderfully since I got her going this past Spring, but, when the summer heat hit, I started having problems with vaporlocking. I replaced the fuel pump (mechanical), and re-routed the fuel line, but to no avail. I've traced it down to the high probability that the aluminum manifold is transferring the engine heat so well to the carb that the fuel is vaprozing in the bowl.

I understand that a phenolic spacer is the typical choice to solve this problem. Typical aftermarket spacers of this type fit the Holley spreadbore, but the hole sizes aren't correct for my carb. The Primaries on my 4360 are 1-3/8" in diameter, and the Secondaries are 1-7/16" in diameter. The holes in the phenolic spacers are made for the typical Holley 4-bbl carb, and, thus, are not direct matches for the openings in my carburetor.

That said, here are my questions:

1. Should I be looking for the open style or 4 hole type phenolic spacer?

IN ALMOST ANY COMBO USING AN RV CAM A 4 HOLE SPACER WILL BE MORE BENEFICIAL
verify with the supplier that the spacer fits your carb, before you purchaser it, but a 1" phenolic spacer with larger holes should work fine, if you can,t locate a 1" spacer you could use two separate 1/2? or 5/8" spacers stacked with a gasket between and under the carb and under the space
http://www.summitracing.com/parts/ctr-85-250
2. How thick should I get?
ID SUGGEST A 1" spacer
mor-64941_w.jpg

3. Will the difference in hole diameters affect the proper performance of my carburetor and engine?
if the spacer holes are larger its unlikely to matter,

4. Will adding a spacer affect the performance of my 4360/283 combination, and, if so, in what way?
ITS LIKELY TO KILL A SMALL BIT OF LOW RPM ,OFF IDLE TORQUE BUT GAIN SOME UPPER RPM POWER

5. Will adding the spacer require a change in my jets?
YOU WON,T KNOW WITHOUT TESTING BUT IN MANY CASES YOULL NEED TO INCREASE EITHER JET SIZE OR LOWER THE POWER VALVE VAC SLIGHTLY, YOULL KNOW AFTER TESTING AND ITS NOT A DIFFICULT DEAL TO CHANGE JETS, TO GET THE FUEL AIR RATIO WHERE YOU PREFER

Thank you all in advance for your help!

- Todd W. White
 

Todd_W_White

New Member
Thanks for the FAST reply!

With regard to the jetting issue - would reducing the thickness to, say, 1/2", still function to effectively insulate the carb from the engine heat, yet reduce the possibility of having to change the jets?

THANKS again!

- Todd
 

grumpyvette

Administrator
Staff member
its unlikely to "need" a jet change with either spacer thickness,because the change will be minimal, I doubt youll notice any significant change other than a reduced tendency to get into vapor lock, but in most cases it will run a bit better if you take the effort to read the plugs and increase or decrease the jetting to match what the plugs indicate is required, so in most cases your going to "WANT TO CHANGE AFTER DIAGNOSING THE TRUE FUEL/AIR RATIO" but only testing after the swap will truly tell.
I can assure you that in my experience the vast majority of guys carbs need tuning to run at max efficient
Id also point out many plastic carb spacers used alone are next to worthless at isolating the carb base from manifold heat.
a combo of the aluminum shield layered gasket over the manifold with the phonelic spacer on top under the carb usually works
http://www.summitracing.com/parts/mrg-3710/overview/
heat1xc.jpg

fordcarbbucket.jpg

ford used to insulate the hot engine compartment air from the carburetor with a carburetor barrier enclosure
http://www.summitracing.com/parts/aaf-a ... /overview/
heat2xc.jpg


RELATED INFO
viewtopic.php?f=55&t=3172&p=16441&hilit=vapor+lock#p16441

viewtopic.php?f=70&t=202

viewtopic.php?f=55&t=109

need a vacuum port access on a carb spacer??
http://www.jegs.com/i/Trans-Dapt/969/2103/10002/-1
969-2103.jpg


http://www.jegs.com/i/RPC/707/R2103/10002/-1
707-r2103.jpg


http://www.jegs.com/i/Mr-Gasket/720/4945/10002/-1

720-4945_2.jpg
 
Last edited by a moderator:

Todd_W_White

New Member
Thanks for all your help!

One last thing - I've been looking around at various designs for these spacer/insulators.

In my case, what do you think about one like this one?

edl-9266_cp_ml.jpg
 

grumpyvette

Administrator
Staff member
Todd_W_White said:
Thanks for all your help!

One last thing - I've been looking around at various designs for these spacer/insulators.

In my case, what do you think about one like this one?

edl-9266_cp_ml.jpg
insulspacers.png

if its at least 1" thick or you use two , stacked with a gasket between them, that are 1/2" thick and they are insulating material like phenolic composite it will work ok

BTW, in some applications adding a carefully cut and placed screen, under the carburetor spacer can be added too catch debris that might fall into the carburetor,and save you a good deal of engine damage , with the potential added benefit that the screen tends to increase fuel air atomization, by breaking up fuel droplets as they enter the plenum, area of the intake, a screen with 1/8" holes has only a minor effect on air flow rates
carbscreena.jpg



a few related calculators and links


http://www.wallaceracing.com/chokepoint.php

http://www.wallaceracing.com/chokepoint-rpm.php

http://www.wallaceracing.com/calc-cfm-head.php

http://www.wallaceracing.com/ca-calc.php

http://www.wallaceracing.com/area-under-curve.php

http://www.wallaceracing.com/calchpaf.php

http://www.wallaceracing.com/throttle-blade-diameter.php


http://www.wallaceracing.com/runnertorquecalc.php

http://www.wallaceracing.com/intake-runner-length.php

http://www.bgsoflex.com/intakeln.html

https://www.rbracing-rsr.com/runnertorquecalc.html

http://racehead.com.au/designing-performance/what-size-itb-should-i-use/
Varying-Intake-Runner-Length.png

Wave-Pulse-RPM-Chart.jpg



http://garage.grumpysperformance.co...alves-and-polishing-combustion-chambers.2630/

http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/

http://garage.grumpysperformance.com/index.php?threads/valve-seat-angles-and-air-flow.8460/

http://garage.grumpysperformance.com/index.php?threads/more-port-flow-related-info.322/
 
Last edited by a moderator:

grumpyvette

Administrator
Staff member
I don,t think anyone will seriously debate the point that removing the divider on a dual plane intake plenum and there by increasing the available plenum volume and accessible flow rates has the potential to significantly increase the power in any application where the divider is effectively restricting flow such as the 496 bbc mentioned above, but a properly selected and matched single plane intake used in the similar combo has the potential, to improve even on those numbers.
as an example one of my neighbors, back in the mid 1970s bought a used 390hp 454 engine, burgundy color, 4 speed corvette and added a hood with a raised aftermarket L88 hood bulge, for more clearance ,and long tube, side mount headers,
hok-2222-1hkr_w.jpg

his first actual engine mod was cutting the intake divider ,out on the stock intake, the second mod was to swap to a wieand or edelbrock single plane intake , both changes resulted in a noticeable boost in seat of the pants power you could feel.
the fact was that the stock oval port intake even with the divider removed was restrictive , and adding the headers allowed even the stock cam to effectively scavenge the cylinders far more efficiently, that cylinder scavenging by effective headers can have a very noticeable effect on the intake efficiency
70vet.png



I don,t remember the model number but it looked a good deal like this summit intake, and we installed a 3 barrel holley on it and it kicked butt
http://www.summitracing.com/parts/sum-226052
ovsg.png

viewtopic.php?f=55&t=3037&p=8012&hilit=+three+holley+barrel#p8012
threbar4.jpg


http://www.vettefacts.com/C3/1970.aspx
 

Wilson1

Member
Ah, the great carb spacer debate. This is always an interesting and polarizing subject. Having been a drag racer for 50+ years I have a garage full of them. All the info here is technically correct, but I would caution that it does not always translate to a real world application. 4 to 8 HP on the dyno might only be .5 HP by the time it gets to the rear tires.

Now I caution all you street guys, drag racing is very different. Drag racers only care about WOT, so some of the things that work on the track, don’t in a street car, and lots of stuff that works in a street car would never translate to a drag car.

This great spacer debate started a long time ago when it was a lot harder to make horse power because of the engine parts we had. People were looking for ways to increase the effectiveness of some components that just weren’t what they are today. Manifolds, heads and cams have come so far in the past 15 years it is amazing. I say this to get you to think about putting some of these posted discussions into perspective. You can either purchase a crate motor or build one that will make way more HP than you could ever use effectively, is fuel injected, and runs like a top.

Don’t’ get me wrong, I am old school, and like street rods that have carbs, rumble and shake and need race gas to run. However, those kind of cars are for a very few. Most people want some improved performance and drivability. I.E. today’s factory hot rods and restro rods are a perfect example of what the technology of the speed industry has made available to everyone. Also lots of guys start building a street rod they enjoy driving, and in a few years of mods, turn it into something they don’t enjoy driving, but it is now one heck of a conversation piece. My point is, most of the new stuff is Fuel Injection. Carb spacers are now not part of the discussion.

If you are like me and love to mess with carbs, and are never satisfied with your combo and always want to try something else, just because it might work, or you are caught up in the trick part of the week club, first I need to extend my condolences, and second I would enthusiastically welcome you to the club. I would like to share some practical knowledge that has worked for me over the years. When it comes to carbs, find a professional, buy a bunch of books and spend the rest of your life learning. Pay for, and go to a seminar put on by a carb professional. Finding a professional and sticking with them will do a lot for you and your program. I have always worked with Gary Williams. I have purchased may a carb from him, and heeded his advice over the years. I have also thought I was smarter than him and tried different things I read about or believed would work better. In the long run, I was always back to his base line. There are many great carb guys out there today, it is almost impossible to go wrong with one.

Here is what I have learned from him over the years about spacers.

Do they work? – You will have to try it to find out. – First Rule Of Carb Spacers.

The taller the spacer, the bigger carb the motor thinks it has. (Think hard about that statement when you put a spacer on your motor and the results aren’t quite what you think they should be before you pull it off an throw it on the pile)

The spacer decreased the angle to the port – Yes it does, but that is mostly only important for Pro Stock motors.

4 hole spacers make good reversion plates if you have a reversion problem at WOT.

If you like the way it looks, and you can tune your motor to make the additional spacer effective, run it. If not, buy another one and try it. It is always cool to impress your friends when they come over to your garage with your collection of spacers. Remember, the seat of the pants dyno is a great tool to justify you spending money on that part, however, it is not a good indicator of increased HP and Torque. I don’t think I have ever spent over two hundred dollars on a part that the “seat of the pants” dyno on my street car didn’t justify the purchase. LOL

Unfortunately with the drag car, I have the time slip to prove me wrong. The point is, you tried it, it didn’t work, but did you learn something? If you did, and it sticks in your brain, someday you might be trying another idea and not getting the results you expect and have a Scooby Doo moment. That other part I tried that didn’t work, that might be just the ticket to work with this new part and give me the results I want.

By the way, this is a lifelong affliction. Enjoy.
 

philly

solid fixture here in the forum
i guess this thread is as good a place as any to post this... what is the general consensus on the velocity stacks that are sold for carbs?? one that has high credentials and testimony is the K&N piece found here:

http://www.knfilters.com/racing/stubstacks.htm

K&N Stubstack®
The K&N Stubstack reduces turbulence, improves metering accuracy. Increases the airflow by reducing restriction. Straightens and speeds up air-flow.

INSTALLATION:
The K&N Stubstack is designed to increase the airflow of carburetors, by decreasing the restriction around the choke horn. The stubstack fits inside the air cleaner housing and slides snugly down over the choke horn. Install holding nut finger tight and use Loctite or 3M to seal. When installed on some models, there may be a slight gap at the base, however this is normal and will not affect the performance of the stubstack. Due to space limitations between the choke horn and some air cleaner baseplates, the stubstack has two thin spots in the casting. These will sometimes crack or chip slightly, but does not affect the performance. Because carburetor castings vary, the stubstack will not fit all carburetors. Check the list numbers for proper application. On some carburetors that are listed, it may be necessary to alter certain areas on the stubstack. The polyurethane material is easily filed and sanded.

AIR FILTER APPLICATION:
The stubstack is designed to only work effectively with K&N Filtercharger™ elements and 360™ custom air cleaner assemblies. If the stubstack is installed in an improper housing, the performance may actually drop! The minimum height above the stack needs to be at least 1-1/2" for proper operation. See bottom of webpage for compatible K&N custom assemblies.
 

Attachments

  • stub-stack-comp-final.jpg
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Wilson1

Member
Air filters and Carb Stacks. Another polarizing subject and one with lots of different opinions. Interesting thing about opinions and articles written by automotive enthusiast, engineers and manufactures is that I truly believe each and every one of them is trying to be as correct as they can be within the context of their study. Here is a link that I believe substantiates that statement.

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

This is a site with several informative articles and all their facts are correct for the average guy that plans on going out to bolt on a few cool items to his hot rod. If you read thru some of them, links at the bottom, the premise is that if you are a regular Joe with a regular car then it is a waste of money. But, the people on this forum aren’t “Regular Joes”.

As “Enthusiasts” when we read articles we are many times looking for justification for a pre-disposed belief or a reason to buy a cool looking part we think might help our program. That enthusiasm many times prevents us from understanding the context of how and why a position in an article or study was advanced. Step back and understand the context of all these independent studies. Then remember, as enthusiasts and hot rodders “We Don’t Need Justification”. Go for it.

The cool thing about a forum like this one, and this is a very unique forum which I just found, is that there is a bunch of people trying to help other people with their knowledge which they have acquired thru either study or experience over the years. What I find unique about this forum is that people are publishing their experience and knowledge without any ego involved. Just how cool is that?

Back to the K&N device. I have run those in the past on my race car with no ill effects. I think the “system” which includes the air filter looks like a very serviceable unit. It couldn’t hurt. I personally believe that the best thing for a street rod is a good cold air intake. Our problem is there are not a lot of options, much less good options for older cars that are off the shelf. Most of the time building a custom on for “our” car is the only option. There are several studies that indicate running air thru a filter before it gets to the carb smoothes out the air flow in of itself and helps performance. I run a flat K&N filter below my scoop on the race car (with no oil on the filter element). Does it work? It didn’t hurt performance that I could tell, and it makes me feel good. So I do it. If you like the looks of that setup, run it. Don’t forget to report back how you felt about the change.

One K&N filter that people seem to believe doesn’t work well is the K&N with the top that is also a filter element. I have read several articles about how that kills HP…. Don’t know firsthand. Anyone with experience with that type of filter?
 
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