HOLLEY STEALTH RAM and other EFI intake manifold info


Staff member
http://www.holley.com/data/Products/Tec ... R10156.pdf

http://www.eecis.udel.edu/~davis/z28/wi ... bpage.html



- FIRST TPI Intake.(good choice)



intake comes with a new throttle body





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




increasing power is in large part the result of increasing the amount of air/fuel mix you can efficiently pack into and burn in the cylinders and the number of power strokes per second that the engine can produce in its effective power range.
the most common mistake made by many people is that they fail to look at an engine as an interconnected group of component sub systems and they don,t realize that changes to a single component, no mater how much potential that component has is not going to allow that component or change in the potential to be realized until all the matched and supporting systems have similar potential.
the heads may be capable of flowing (x) on a stock engine but with careful selection of a cam with the correct duration and lift, and with a tuned header, and matching valve train mods along with some port and bowl clean-up the resulting improvements can be significantly more impressive.








yes they look similar in height but the stealth rams about 7/8ths of an inch taller
you can,t easily machine the original base and upper plenum enough to get the required clearance.
read this thread

EXAMPLE heres how far my stock hood would close with a STOCK un-modified stealth ram intake


After careful measurement and fabrication of a custom test model,plenum, I got it to not only fit but flow better, but keep in mind I own a milling machine and a TIG welder so this is not a project you'll easily complete in your average garage!

stealthram base


stock un-ported runner entrances[/color]

this mod (look at pictures)
definitely is worth the time and effort required, on a friends flow bench theres very noticeable gains, keep in mind the old weakest link in the chain concept , if the heads flow 300 cfm, the intake MUST also flow at LEAST that well.



btw I also port matched the lower runner exits too the head ports

porting the stealth-ram base and port matching the intake too the cylinder heads allowed a 300 cfm flow, its significantly less unmodified

most guys I know have done the port work themselves and yes it takes a lot of time and effort but everyone I know thats done it feels it was worth the effort
don,t forget all that potential extra air flow from a correctly ported stealth ram intake and matching heads that can flow in excess of 300cfm per runner, requires 36lb -44lb injectors and a cam with enough lift and duration to allow that air flow rate to be effectively used if you expect the intake to perform to near its full potential
porting the runner entrances like this helps flow significantly


BTW the stock HOLLEY FUEL PRESSURE REGULATOR ON THE STEALTH RAM, is know to have frequent failures, heres a link to a higher quality unit, part #6547

http://www.kirbanperformance.com/produc ... 36547.html

http://www.holley.com/TechService/Libra ... lInjection

http://www.corvettefever.com/techarticl ... to_08.html

http://www.eecis.udel.edu/~davis/z28/wi ... 21105.html


http://www.corvetteguys.com/mass-airflo ... 4-cat.html

http://www.eecis.udel.edu/~davis/z28/wi ... mrinstall/

http://www.eecis.udel.edu/~davis/z28/wi ... 10511.html

http://www.eecis.udel.edu/~davis/z28/wi ... bpage.html

http://www.eecis.udel.edu/~davis/z28/wi ... 10413.html

http://www.eecis.udel.edu/~davis/z28/wi ... 31229.html

http://www.eecis.udel.edu/~davis/z28/38 ... niRam_(383)_vs_HSR_(350).html

http://www.eecis.udel.edu/~davis/z28/wi ... niRam_(383)_vs_HSR_(383).html

(very useful info here)

TPI Torque Specifications

Below are the torque specifications as designated by GM for Tuned Port Injection intakes. Please note that some specifications are in lb. ft., and some are in lb. in.

Manifold to Runner Bolts 25 lb. ft.
Runner to Manifold Bolts 25 lb. ft.
Fuel Rail Attaching Bolts 15 lb. ft.
Throttle Body Attaching Bolts 18 lb. ft.
Throttle Position Sensor 18 lb. in.
Idle Air Control Valve 13 lb. ft.
Throttle Body Coolant Plate 27 lb. in.
Throttle Body Cover Plate 30 lb. in.
Power Brake Vacuum Fitting 108 lb. in.
Fuel Line Nuts 20 lb. ft.
Fuel Tube Bracket Bolt 25 lb. ft.
Fuel Pressure Connection 115 lb. in.
Pressure Regulator Base to Rail 44 lb. in.
Pressure Regulator Bracket 44 lb. in.
Outlet Tube to R/H Rail Retainer 44 lb. in.

http://www.eecis.udel.edu/~davis/z28/wi ... yno051125/

http://www.eecis.udel.edu/~davis/z28/wi ... yno060404/

http://www.eecis.udel.edu/~davis/z28/wi ... yno060502/

bits of early corvette FI info


as you can see even this EXTENSIVELY PORTED TPI BASE is restrictive to flow
The work was done a http://www.cfmperformance.com and I must say the port work is very well done



then the obvious choice is swapping to a small base HEI fron an F body (camaro/firebird) with a remote mount coil as it almost a direct swap


most dual quad, tunnel ram or similar induction systems require a small diam distributor or vertex mag
its simple enough to tell with a caliper or even a ruler

small cap distributors measure approximately 4" in diam.

LARGE cap distributors measure approximately 5.25" in diam.




be aware that the lower runner gasket is not interchangeable between the drivers and pass sides of the engine on a tpi and if installed incorrectly that results in hard starts a big vacuum leak and an engine that won,t idle
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Staff member

IF you select a HOLLEY EFI your going to NEED THIS INFO
http://www.holley.com/data/TechService/ ... 5rev11.pdf

conversion to throttle body style fuel injection


better fuel economy
slightly better power in a few cases
less fuel/oil contamination
faster starts
lower emissions
slightly lower engine wear

initial cost
learning curve
complexity(some require lap top too tune)
requires different fuel pump(and lines, filter)
some require different fuel tank

equal (obviously depends on choices made)
peak power usually similar
room under hood similar

more info

http://www.thunderracing.com/catalog/?a ... 48&sid=281

btw youll see significant flow rate increases with a STEALTH RAM intake with a few minor porting mods before you install it

theres not much too it you just draw a line in the center of each runner entrance wall in the center (+) between each runner in each quad, on the lower base before you install the plenum,then blend the wall to a sharp edge over the last 1/2" of the runner entrance so the (+) no longer has a 1/4" wide flat entrance but a knife edge that funnels the entrance open increasing the entrance cross section and reducing turbulence at the runner entrance in the plenum floor, don,t touch the outer ring the gasket seals too,now port match the runner exits to match the heads and blend that back a minimum of a full inch into the runner, bevel the plenum edge slightly where it mates to the lower runners and make sure the throttle body does not have a restriction in the plenum entrance area
keep in mind the stealth rams designed to produce its best power in the 3700rpm-6500rpm band and a matched cam timing and head flow rates exceeding 250cfm at .500 lift on the cylinder heads used and having a stall speed and rear gear ratio that keeps the engine in that power band is required to maximize the intakes potential, that will generally require a cam in the 230-245 duration range, matched compression, displacement of at LEAST 350-383 cubic inches and a cam with more than about .520 lift, yes it will provide benefits with other combos but matching its characteristics to the application will help a great deal

BTW To remove the connector from the injector, push carefully in the middle of the locking clip, with your thumb, This will make the sides, and tips move OUT WARD in their connector slots allowing the tips that hold the injector into the connector to slide out of the way from the injector body, and you can then pull the sides away. WATCH the locking clip - IT can and WILL come off and get lost, if your not careful

http://www.harborfreight.com/180-piece- ... 1b2166c2c0
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Staff member
both the STEALTH RAM AND FIRST INTAKES are high flow rate improvements over the basic TPI system, the FIRST has the huge advantage that it fits under the stock c4 hood line!
both can be ported and BOTH can produce very good hp nembers. both work in aproximately the same 3000rpm-6000rpm band with the FIRST coming in at about 2500rpm-5500rpm, and the holley at about 3500rpm-6500rpm , due to runner length and other factors, but both require the correct matched components, to maximize thier potential, and that increased air flow will require a matching increase in fuel injector size if you want to reach decent hp levels, youll want a MINIMUM of a 30lb to take advantage of the increased flow rates and might need a 36#-42# injector size in each port depending on your combo

http://www.gmhightechperformance.com/te ... index.html



http://www.eecis.udel.edu/~davis/z28/wi ... 21105.html

The first thing I always do is, instantly reach for and read the installation manual,
and start looking on the internet for related info,
when confronted with projects like that EFI control harness instal.
with experience, you learn you have too read carefully and pay attention to foot notes/
you also eventually learn to try too find several people that have previously installed and wired up the system
, and done programing, and trouble shooting..







Some more information





Satin FIRST® manifold without electronics. Prices starting at $999.95

All intake manifolds without electronics include all required gaskets, all stainless steel hardware, TPS bracket, throttle bracket, and fuel rails.

keep in mind you need to exactly match the compression ratio and head flow and exhaust scavaging rpm bands and the drive trains gearing too maximize the intakes flow charicteristics........something I doubt was done in those dyno runs
the first intake or the holley stealth ram should be matched to a 3000rpm stall, 3.73"1 rear gear, a 383-427 displacement engine with about a 10.5:1 cpr, heads that flow a minimum of 250 cfm at .500 lift (270cfm at .500 lift would be better) and a cam with about a 230-235 duration to match the intakes flow range

I found this info and I figured you guys might like to look it over, now the first thing I want to point out is where the DATA came from. and KEEP IN MIND ITS REAR WHEEL HP AND The TPI INTAKE IN THE TEST consists of 58mm TB, fully ported plenum, AS&M largetube runners, and highly ported Edelbrock base WHICH MEANS ITS ALREADY MAKING AT LEAST 25HP-30HP MORE THAN A STOCK TPI INTAKE)


The engine was basically the same,in all the test except for the intake manifold, consisting of a ZZ4 crate motor, AFR190 heads, LT4 HOT cam, and SLP 1-3/4" SS headers. Trans is a 700r4 with a Vigilante 2800 stall converter. The Engine Control Module (ECM) was a '92 TPI stock ECM (MAP/speed-density) with a modified EPROM.


TPI engine.....283 PEAK rwhp @4800rpm peak
AVG. TQ 291.5
AVG HP 269.5

303 PEAK rwhp @6200rpm peak
AVG. TQ 285.8
AVG HP 269.1
IT LOST 29 HP at 3800 rpm and MADE 48 MORE HP THAN THE stock TPI at 6300 RPM

stealth ram
342 PEAK rwhp @6400rpm
AVG. TQ 319
AVG HP 300 it lost 28 hp at 3600 rpm BUT GAINED 66 HP AT 6600 RPM
over the stock TPI
342 rear wheel hp is aproximately equal to 427 flywheel HP FROM A 350 SBC ENGINE, figuring a 20% driveline loss rate.

the use of a longer duration cam and only measureing PEAK HP would tend to benefit the miniram and STEALTH RAM intakes to a MUCH GREATER extent than the TPI, THATS HOW claims of gains of 100hp are made for some intake combos, while its TRUE that you can make in excess of a HUNDRED EXTRA hp at 6600rpms is due more to the TPI not being able to flow air (LOSSES) keep in mind that a LARGER ENGINE DISPLACEMENT WOULD BENEFIT EVEN MORE from the steathram

IF you look thru the combos linked below carefully youll see that it takes a decent combo of heads, displacement and cam timing and gearing to take full advantage of the increase in intake flow potential
heresa site with several combos


btw the holley benefits from porting the runner enterances noticably
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Staff member
want a killer SBC? slap one of the better flowing intakes above on an engine combo like this one below and add a cam like this crower below with 1.6:1 roller rockers

http://www.crower.com/misc/cam_spec/cam ... &x=30&y=11


and a 10.5:1 cpr, match it to 42 lb injectors, a 3.73 rear gear and a manual trans or an automatic with a 2800-3000rpm stall converter in a reasonably light car

and a good set of full length headers on a low restriction exhaust

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













I was asked what combo of parts ID use if I was going to build a tuned port intake based small block chevy engine.
well the first step would in my mind to select the currently best flowing TPI style intake which is the FIRST DESIGN,(keep in mind the basic TPI intake design is set up to maximize mid rpm range torque,with its longer ram tube intake runners, so Id build it based on a DART BLOCK,built to be a 406-to-427 displacement with 6" rods with 7/16" ARP rod bolts and an internally balanced 4340 forged crank, forged pistons and 10.5:1 compression.
obviously increasing the displacement, from 350 cid to 406 or larger , and bumping the compression up into the 10.5:1 range and changing the roller cam timing from about 210 @.050 to the higher 235-240 @.050 duration and high mid .550-to-.600 lift range will help, but swapping too much better cylinder heads matched too a far better flowing intake than the restrictive stock TPI, and adding tuned headers , that are tuned for scavenging those cylinders, as a matched combo can DOUBLE the power and significantly increase the rpm range, and adding low friction 1.6:1 ratio roller rockers sure won,t hurt.
but to access that higher rpm range a 3.54:1-3.73:1 rear gear and a 3200 rpm stall converter are near optimal.



this is the no longer in production accell super ram, in my experience its not quite as good as a mildly ported FIRST FUEL INJECTION INTAKE
an intake alone may help but its a well thought out complete matched set of components that give the best results by far.

THE larger 1.75" (2.45 sq inch cross sectional area)of the FIRST intake design, vs the STOCK 1.47" diameter runner cross section (1.7 sq inch cross sectional area), of the stock G.M. tpi, intake adds at least 1200 rpm to the engines potential IF properly matched to the correct components, like 42lb injectors, un-ported this runner should provide peak power in the 4500 rpm-6000 rpm range, while the stock TPI intake runners peak at least 1200 rpm lower, near 4400 rpm where they tend to start restricting flow
keep in mind that without decent flowing aftermarket heads and a reasonable hydraulic roller cam with at least a 220 -to about a 235 duration at .050 lift cam, and .540-maybe a .580 lift , with matched roller rockers and a free flow low restriction exhaust plus a decent 3.54:1-3.73:1 rear gear and a manual transmission or a 2800 rpm-3200 rpm stall converter you can get the improved flow potential of those intake improvements to maximize the engine true potential.

Id select decent flowing heads like these
these 1.6:1 ratio roller rockers
a cam like this, if your goal is max peak power
a cam like this, if your goal is good driveability on the street with good power
http://www.summitracing.com/search?Sort ... er%2000471
a cam like this, (crower above)if your goal is good driveability on the street with good power, but your willing to put up with some low speed driveability issues to get more power (it basically splits the difference,I tried all three and went with the smaller crane roller

a good quality 7-8 quart oil pan with windage tray
these valve covers
http://www.proformparts.com/product-exe ... ory_id/249
a high flow water pump
and a vertex magneto ignition
Id match that with a 3.73:1 rear gear, 4l80E transmission and 3300rpm stall speed converter
Inj Flow Rate (@ 40psid) Naturally Aspirated hp (@ 0.50)
19 lb/hr 258 hp @ 85% Duty Cycle
24 lb/hr 326 hp @ 85% Duty Cycle
30 lb/hr 408 hp @ 85% Duty Cycle
32 lb/hr 435 hp @ 85% Duty Cycle
39 lb/hr 530 hp @ 85% Duty Cycle
42 lb/hr 571 hp @ 85% Duty Cycle
47 lb/hr 639 hp @ 85% Duty Cycle
60 lb/hr 816 hp @ 85% Duty Cycle

before you go starting to buy the components keep in mind theres other options, something like a 570hp/570 ft lb TPI combo could be built, but your could exceed those numbers easily with a turbo LS engine or 496-572 big block swap










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Staff member
there are TWO differant FUEL PRESSURE REGULATORS available from HOLLEY,

the ADJUSTABLE one has a screw adjustment with NO VACUUM CONNECTION,

the standard fuel pressure regulator has a vacuum connection and NO SCREW ADJUSTMENT

and NO THERE SHOULD NOT be fuel leaking and the ragged idel hunt problem sounds very much like a vacuum leak between the plenum and the runners (comon if you dont use sealant on both sides of the gasket) or don,t tighten the plenum evenly) and hard to spot but you can test for it easily with a propane torch, turn it on and just DON,T light it and point it at any suspected leaks, the idel speed will go up noticably if a leak sucks propane into a runner thru a leak

classic symptoms of a vacuum leak.
first check and set the ignition timing correctly

yeah the way I find vacuum leaks is clean and easy with no mess. get a propane torch,

(DONT LIGHT IT) just SLIGHTLY open the valve so its allowing gas to flow at a low voluum,start the engine and let it idle at the lowest speed you can then place the tip of the UNLIT torch at any suspected vacuum leak and listen for the rpms to increase and watch the tach, gas flowing into a vacuum leak will increase engine speed. BTW since your running EFI also carefully check to see if the little wire on your MAF is busted and that the TPS is set to the correct voltage ( LOOK IN MANUAL, I think its .54 volts) and no vacuum hoses are loose or disconected or wire to injectorsa are loose

BTW if you take the plenum off you can make far better that factory paper gasket from the 1/16" thick 4"x4" gasket material sheets made from rubberized canvass that most hardware stores sell by tracing carefully a factory gasket and cutting new REUSEABLE rubber ones, that seal far better and dont require sealant to use

and you can increase air flow at the ports by thinning , porting and blending the center (+) between the runners to open and smooth the runner enterance, just dont touch the outer wall where it seals to the plenum

and your correct about the strealth ram, its an EASY 60 plus hp over a stock TPI intake if you run a cam like IM running (crane 119661) and heads that flow enought air to benefit from the intakes much higher air flow

BTW I think youll want to look this over




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Staff member
you may want to read thru these for ideas

headers and a good free flow exhaust are a good place to start , adding a cam is probably the most effective use after the headers, and once the headers and cam are in ID SERIOUSLY consider good aluminum aftermarket cylinder heads, keep in mind that your heads,cam and intake are seriously restricting your potential and swapping to a 3.73 ratio rear gear helps a bunch
I got the largest gains from installing good aluminum aftermarket cylinder heads,and stroking/boring the engine to 383 with a boost in compression, I installed a set of personally ported TRICKFLOW heads and a PORTED INTAKE,, adding a cam and a extensively ported STEALTH RAM intake , was a big boost





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Staff member
I don,t have access to a camera at the moment but the feed enters at the pass side rear of the fuel rail and the return exits the drives side rear near the pressure regulator location with the cross over feed between the fuel rails under the throttle body
the advantage is that it minimizes the fuel lines in the engine compartment where the fuel lines can absorb heat and the feed from the front of the fuel rail would tend to cause clearance issues with the linkage if it entered on the drivers side, and IAC clearance issues on the pass side, and a cross over on the rear tends to make access to the distrib wiring and turning the distributor for timeing more difficult, yes it can be done but these no advantage, BTW before you go thinking of adding BOTH a front and back cross over, "been there, done that" theres no change or advantage, its just a nicer cleaner install doing it from the rear feed/return, look at the picture


HOLLEY changed the STEALTHRAM casting to a thicker flange a few years ago , notice the lower intake is marginally thicker allowing larger ports to be cut when porting

LINK TOO instructions, BELOW,
rough and smooth are fairly relative terms, smooth in an intake runner generally refers,
too the mirror like surfaces that were almost thought too be mandatory in the 1950s-early 1960s
but you certainly can,t get a "smooth surface texture "
with anything in a flapper wheel of 80 grit or larger grit











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look on page 10 for a picture, then hit the plus to enlarge it


http://www.rodandcustommagazine.com/tec ... index.html



stock un-ported runner entrances[/color]



most guys I know have done the port work themselves and yes it takes a lot of time and effort but everyone I know thats done it feels it was worth the effort
don,t forget all that potential extra air flow from a correctly ported stealth ram intake and matching heads that can flow in excess of 300cfm per runner, requires 36lb -44lb injectors and a cam with enough lift and duration to allow that air flow rate to be effectively used if you expect the intake to perform to near its full potential,
no! your stock hood clearance prevents this stock stealth-ram intake from fitting under a stock c4 corvette hood. without a hood scoop that adds about an additional inch or more, of hood clearance.
yes a custom plenum can be fabricated, but its not particularly cheap or easy to do, and you damn sure need to measure carefully and know how to weld, port and machine aluminum,

porting the runner entrances like this helps flow significantly
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Staff member
RedGut86 said:
I've been lurking around on here from time to time and have read your posts on here and a few other forums and when I read your thread about ask me questions I just had to ask, I would really like to pick your brain about my combination!

I've read pretty much all of the books you suggest and in fact my combination is out of John Lingenfelter's book. It is the classic 10.3:1scr, 383 (5.7 rods), Accel Super Ram intake and Lingenfeter 219/219 .560/.560 lift (w/1.6s) camshaft. Instead of using reworked corvette heads I used Dart 200cc Pro1s which were ported by More Performance in NC I've attached the flow numbers,
http://img.villagephotos.com/p/2005-7/1054060/flowsheet.jpg The car has Scorpion 1.6 roller rockers, 52mmTB,
1 5/8" long tube headers. The car (actually a corvette but none-the-less) weighs around 3300lb wet and has a 3.07 rear gear. I think that is about all of the specs, let me know if you want more.

Now I like the Super Ram (for at least the peak 500rpm before it just starts to fall off) but I feel like I actually have some pretty darn good heads on this motor and I'm killing them. The idea that this long runner super ram that has decent flow is feeding into these big heads that flow pretty well just makes me think I'm leaving a lot on the table and I could have a much more responsive, and more powerful motor without that choky intake on there.

Now as a fun project I think it would be pretty cool to use single plane EFI setup. I'd probably try to use an existing EFI manifold (Holly, Victor EFI, or pro products super hurricane) as I worry about the correct angle for drilling for injectors. Then run a box style plenum on top of that and have it connect up to the classic TPI TB in front. (Sort of like what Edelbrock has released) This would fit in the car with minimal fuss and I think would better be able to take advantage of head air flow. My one obstacle being total manifold height, so the plenum/box will be pretty shallow in height (~9" total clearance, but I think I can make it work.)

Now it won't be a max effort motor, I'll still drive it around town on weekends and I still love torque but I doubt with 383cid it will be too down on that. I'd probably run it initially with the small Lingenfelter cam but eventually go to something in the 234/244 range that winds up higher. (I'd probably want to shift ~6500rpm tops for reliability purposes.)

So I guess my question is really, looking at my current combination, is my logic correct?

Could I gain more by going to the higher flowing intake?

Is the single plane EFI truly going to still give me good tq down low but with intake wave harmonics obviously moving the peak power up higher in the rpm band?

Anyway, sorry for the long winded post. I've tried to scour the internet looking for people using these 383 EFI combinations but there aren't a lot out there really. A lot of them are blown but it seems like especially with the new heads (AFR 195 Comps) that flow so well, these TPI intakes could really negate how good these heads really are.

Thanks for the time, I really appreciate your knowledge and insight!

Chris Carosino

IT JUST SO HAPPENDS, that I ran this intake


this distrib

http://www.holley.com/HiOctn/ProdLine/A ... 0-160.html

this throttle body

http://store.summitracing.com/partdetai ... toview=sku

this TB adapter
#74882 (btw its ANYTHING BUT NEW its been available for years)

and this cam

http://www.crower.com/misc/cam_spec/cam ... 1&x=39&y=8

in an 11:1 cpr 383 with 36 lb injectors

(all numbers are flywheel hp)
it was a HUGE improvement over an extensively PORTED TPI intake, and it made about 60 hp more than the tpi intake which made about 360hp,on the same combo and made a good deal more hp ABOVE 4000rpm,(so it made about 430hp) mostly due to the far better flow rates BUT noticeably less TQ below 3000 rpm
I then swapped to an extensively ported stealthram, gains were minor but noticeable at about 450 hp, I then changed to a full length 3" exhaust and it jumped up to around 478hp , further tweaks/tuning improved things to the mid 480hp range.

hope that helps


Staff member
nearly anyone working on any corvette can at some point screw up some component, and cause a fuel leak or an electrical fire that destroys a car.
Ive occasionally used nitrous on my corvette for over 10 years now, and and never had a single issue.
the stealth ram and a few other intakes are or can be easily modified to be excellent intake designs to add a nitrous boost to your engine, youll occasionally see guys that will tell you nitrous is dangerous or can burn up your engine, and while thats possible if the installations not done correctly its far from probable.
thousands of guys have run nitrous on engines with zero issues.
saying nitrous will destroy your engines a bit like saying women only get married so they can collect alimony, while it no doubt happens its far from the most likely outcome.
anyone working on the electrical or fuel system on any car has the potential to screw things up and can cause a fire that destroys a car. adding nitrous is not the cause,but a crappy install or defective components can be and is far more likely, the cause if you have problems.

http://www.jegs.com/i/NOS/741/05151/100 ... ProductId=

http://www.gmhightechperformance.com/te ... index.html









Staff member



HERES EDELBROCKS newer EFI ram intake above
(designed mostly as a mid and upper rpm power band EFI intake)
and a version of mercury marines ram jet EFI for boat engines below
(designed for low and mid rpm power, notice the smaller runners and plenum)











Have one to sell? Sell now
Weiand 6221 Offset Thermostat Housing Adapter For Small Block and Big Block Chev
your problem is VERY COMMON, if the throttle body and thermostat housing has a clearance issue on some modified EFI intakes, heres the usual cure

its rather obvious the new edelbrock efi intake is smaller and uses shorter and more direct runners like a tunnel ram

having the bracket and linkage extend above the manifold plenum height is a huge clearance issue with lower hood clearance

the otherwise reasonably compact manifold has the throttle body , mounted high to clear the thermostat housing and this results in a huge clearance issue with low hood clearance, nothing can extend higher than about 8.7" from the front block china wall on the block if the c4 corvette hood will be expected to clear and close


the dyno chart below seems to show the smaller runner cross sectional area provides decent torque from lower rpms , but the rapid drop in torque from about 4800 rpm and higher may be , and looks very much like ,the result of the ports restricting air flow


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Staff member
Im always rather amused at the newer guys that seem to think you can take an intake manifold out of the box and install it on an engine, especially an engine they want to maximize the power from, without a series of minor port clean-up and port matching.
I had one of the guys I know call to tell me his car didn,t run nearly as well as he expected it too with a new carb and intake manifold, I asked a dozen questions for which all I got was that (DEER IN THE HEAD LIGHT STARE" and it became very obvious that he neither understood the need or even the reason you (PORT MATCH an intake or how to tune a car, or even what to look for to determine the cars fuel/air ratio, ignition timing,or a dozen other factors that will effect his results.
I gave him a couple dozen links to look thru which I doubt he will take the time to read thru , yet he will still expect the parts he purchased and installed to work better than they currently do!
the fact is that damn near every part you use can have minor improvements made to its function or durability, but it takes some time, research and effort....something , of a concept, that some guys never grasp!
a simple thing like correctly port matching your intake and a cylinder head bowl area port clean up might not give you a huge jump in performance, nor will taking the time to degree in your cam,adding a transmission cooler,learning to adjust throttle linkage, adding a clutch fan, or an oil cooler,learning to correctly adjust your rockers or verify your ignition advance curve,checking and adjusting your fuel pressure, verify your coolant temps,verify your alternator voltage, verify your ignition wire resistance, install a high capacity oil pan and windage tray,adjusting carb floats, or injector resistance and flow pattern,set you TPS sensor, verify the temp sensor readings, verify the t-stat functions,check your fluid levels, use a low restriction oil ans air filter, route cold outside air directly to the throttle body or carb,or verify your exhaust back pressure at wide open throttle, in some cases, but youll be amazed at how much better the engine runs when you check and do all the little things
selecting the correct parts the first time is obviously a huge help in getting to your goals but its all the little tweaks and mods and attention to small details that changes a good combo to a great combo!
bytor said:
Came across this info while doing some research and thought I'd share.

TPI Intakes and runners

The following airflow tests were performed on the University of Northwestern Ohio's SuperFlow SF600 Flow Bench. All CFM values are corrected for airflow at 28 inches of water. Injector flow rates are flowed at 43.5 PSI on an injector flow bench using test fluid with same density as gasoline.


Stock TPI/LT1 48mm Throttle Body w/o airfoil -- 783.0 cfm

Stock TPI/LT1 48mm Throttle Body w/ airfoil -- 821.9 cfm

TPI/LT1 52mm Throttle Body w/o airfoil -- 848.9 cfm

TPI/LT1 52mm Throttle Body w/ airfoil -- 898.8 cfm

Stock 98 Camaro 3800 II Throttle Body -- 554.3 cfm

Stock TPI Bosch MAF sensor w/ screens -- 517.8 cfm

Stock TPI Bosch MAF sensor w/o screens -- 658.4 cfm

Stock 87 GN 3.8L Turbo AC MAF sensor w/ screen -- 584.2 cfm

Stock 86 2.8L AC 5-wire MAF sensor w/ screen -- 576.2 cfm

Stock 96-up AC 3100 V6 MAF sensor w/ screen -- 616.4 cfm

Stock 96-up AC 3100 V6 MAF sensor w/o screen -- 670.7 cfm

Stock 94-up LT1 MAF Sensor w/o screen -- 719.0 cfm

Stock 85-87 Firebird TPI airbox mid piece -- 499.3 cfm

Stock 4.3/5.0/5.7 2bbl TBI complete -- 574.1 cfm (dry)

Stock 4.3/5.0/5.7 2bbl TBI w/o injectors -- 584.7 cfm

Stock 3800 vin L throttle body w/ screen -- 419.1 cfm

Stock 3800 vin L throttle body w/o screen -- 444.8 cfm

4bbl MPFI Holley Throttle Body -- 1287.6 cfm

Another source sent in these flow numbers

Flow and HP ratings for Throttle-bodies:

Flow (cfm) Max. NA HP
Stock 668 300
Stock w/airfoil 710 350
52MM w/airfoil 835 400
54MM (AS&M) 900 450
58MM 1050 500

TPI Intakes and runners flow rates

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm

the stock TPI has a hard time flowing 230cfm even with minor port work, look here
most of this info is right off the accel,holley,edelbrock, and TPIS sites, add a little math and the results become much clearer!!!

Intake....... length ....... port in -- out
Stock GM Base--- 6.375"------ 1.47"- 1.96x1.2
TPiS base------ -6.125"------ 1.75"- 2.09x1.28
Accel base----- -6.125"------ 1.75"- 2.09x1.28
Holley base------- 6” runner 2.3”- 1.9”x 1.23 (2.337 sq inches)
Stock TPI----- -- 7.250"------1.470" round(1.70 sq inchs)
SLP ----------- - 6.625"------1.600" round (2.01 sq inchs)
Accel LTR------- 6.625"------1.615" round (2.05 sq inchs)
TPiS----------- 7.625"------1.660" round (2.168 sq inchs)
Mini ram -----3.5”
LT1 ----------3”

Runners (measured individually)
Stock....................203.17 cfm
ACCEL................242.02 cfm
Extrude/ACCEL...275.83 cfm
Super Ram............289.18 cfm
Intake manifold with 3/8 inch radiused intlet.............................222.45 cfm
Holley stealth ram ………..275cfm

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm
Holley stealth ram …..275cfm

ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.........251.51 cfm

ACCEL Hi-Flow intake manifold with runner
Stock....................215.83 cfm
ACCEL................232.53 cfm
Extrude/ACCEL....243.21 cfm
Super Ram............240.24 cfm

Extrude-Honed ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet ...............275.83 cfm
Extrude-Honed ACCEL Hi-Flow intake manifold with ACCEL runner ..............266.94 cfm
Edelbrock Performer RPM manifold (Stock)..........286.51 cfm
Edelbrock Victor Jr. ............275.24 cfm

the HOLLEY STEALTH RAM FLOWS at 275cfm out of the box, and has the potential when matched to the correct heads and cam to totally out flow most other intakes available,can easily reach 300cfm with minor port work and costs much less
Stock…………………………… 275cfm

Runner lengths
Stock tpi manifold 8” runners 11.25”, cylinder head 6” total 25.25”
Accel super ram manifold 8” runners 7” cylinder head 6” total 21”
Holley stealth ram manifold 6.26” ” cylinder head 6” total 12.26”
Edelbrock performer RPM runners 6” ” cylinder head 6” total 12”
Edelbrock vic jr , runner length 5.5” ” ” cylinder head 6” total 11.5”

Also interesting TPI mods. Not so sure I agree with the one on bumping up the initial timing.

Basic TPI modifications
Friday, May 23, 2014

bytor said:

Volume (CCs) of Head Gasket
CCs of Head Gasket = Bore x Bore x 12.87 x Thickness of Head Gasket
felpro # 1204=Port Size: 1.23" x 1.99"=2.448 sq inches

felpro # 1205=Port Size: 1.28" x 2.09"=2.67 sq inches

felpro # 1206=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1207=Port Size: 1.38" x 2.28"=3.146 sq inches

felpro # 1209=Port Size: 1.38" x 2.38"=3.28 sq inches

felpro # 1255 VORTEC=Port Size: 1.08" x 2.16"-2.33 sq inches

felpro # 1263=Port Size: 1.31" x 2.02"=2.65 sq inches

felpro # 1266=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1284 LT1=Port Size: 1.25 x 2.04''=2.55 sq inches

felpro # 1289 FASTBURN=Port Size: 1.30" x 2.31" 3.00 sq inches

Your RPM computed from your Cross Sectional Area of 1.95
(the smaller AFR HEADS)
and Bore of 4.03 and Stroke of 3.75 is 5,569.12 .

Your RPM computed from your Cross Sectional Area of 2.05
(the Larger AFR HEADS)
and Bore of 4.03 and Stroke of 3.75 is 5,854.72 .
you,ll barely notice the about 300 rpm shift in the power band on the lower part of rpm range but appreciate it much more on the upper edge of that power curve

heres a chart FROM THE BOOK,HOW TO BUILD BIG-INCH CHEVY SMALL BLOCKS with some common cross sectional port sizes
(measured at the smallest part of the ports)
...........................sq inches........port cc
edelbrock performer rpm ....1.43.............170
afr 180.....................1.93.............180
afr 195.....................1.98.............195
afr 210.....................2.05.............210
dart pro 200................2.06.............200
dart pro 215................2.14.............215
brodix track 1 .............2.30.............221
dart pro 1 230..............2.40.............230
edelbrock 23 high port .....2.53.............238
edelbrock 18 deg............2.71.............266
tfs 18 deg..................2.80.............250


Basic TPI Mods: by DEBBIES87

There are a few basic mods that should be done to any TPI car, I call these "entry-level" modifications.

1) Cut the air box open without letting air in the engine without going through the air filter & remove the additional plastic piece below the air box to get more air into the engine.

2) Modify the mass air sensor; remove the screens, & and if your brave cut down the fins.

3) Port the plenum (upper intake). There are two small ridges sticking up in the entry-behind the throttle body, remove these. The throttle body openings are already 52mm, so don't go crazy when porting.

4) While the plenum is off for porting, it is now a good time to get a adjustable fuel pressure regulator & a MAT sensor relocater kit. The Adj. FPR will aid in tuning, and the new MAT sensor will improve throttle response as well. The new LT1 style MAT sensor is placed in the air box instead of the plenum, this allows it to read cooler air and advance the timing accordingly.

5) Advance the base timing to 12-13 degrees. Note: the harmonic balancers on these cars tend to drift with age, adjust timing to where the car still starts good and doesn't detonate.

6) If legal in your area, gut the catalytic converter and remove the smog pump belt (85-87), or run a shorter serpentine belt to bypass the pump (88-92); you will need to remove the smog pump on the 88-92's to reroute the belt properly. Check local smog laws first.

7) On automatic cars, adjust T.V. cable (throttle valve cable), so that the car shifts out between 4200-4500 RPM under wide open throttle. TPI motor power drops off drastically after 4500-4700 RPM, they peak at about 4200-4400 RPM. No need to over-rev these motors.

8) Bypass fan relay to make fans come on manually, or install aftermarket relay to turn on fans sooner.

All together these mods should make the car perform like it should have from the factory, gains should be between .6-.9 tenths of a second from these modifications.


so how many of you guys have found out small details combine to make a noticeable difference??








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Staff member
Id point out that the MATH that many guys think is a rock solid fact on flow numbers won,t always add up the way they assume it will!
I recently got a call from one of the guys I went to high school with thats , kept in touch as we have a similar hobby ,hes building what he assumes will be a really fast TPI based engine for his 1987 corvette!
yes a 383 SBC with the proper selection, of up-graded aftermarket heads and a new cam, can provide a significant power improvement , but a good deal of the intakes efficiency depends on matched compression,cam timing valve lift and duration, effective exhaust scavenging and a low restriction exhaust.
the problem he called about was his concerns over the fact that in his mind his machine shop, must be lying to him, the machine shop has a flow bench and they told him his recently ported , aftermarket TPI intake now flows 267 cfm,and he was assured his recently ported heads are rated to flow 272 cfm so hes very upset, he swears that the machine shop bolts them together adds a throttle body to the plenum and it now flows only 236 cfm as a combined assembled combo
I assured him that the combined flow rates almost always drops significantly and that was rather common, the stock TPI heads rarely flow over 210 cfm when mildly ported the stock TPI intake flows less than 200cfm and combined your lucky if a stock TPI intake and head port get to flow 180cfm.
I also pointed out that the direction of air flow might easily have been measured on the flow bench with the air flow moving in the opposite direction on the two separate tests , its rather common to measure heads with the air flow going in the standard direction ,but many intakes are flow tested with all the ports but one temporarily blocked with duct tape and the carburetor base or throttle body base on the flow bench, thus combined flow and interaction of individual runners is not nearly correct, just because each individual runner flows lets say 167cfm does not indicate all 8 will flow 8 x 167. or over 1300cfm

there has been a way or math formula too roughly guess at an engines potential max likely power output for several years, it assumes most of the components are correctly matched and no power adders are used.
based on combined port flow, example if each port flows 200cfm x 8 cylinder x .257= likely peak power or 411 hp in that case, and yeah, its not always exact but it gets you in the power ball park most of the time
GIVEN THE PREVIOUSLY MENTIONED 236 CFM on the TPI ABOVE mentioned earlier the wild guess of that math formula puts that engines power peak potentially near 485 HP, CERTAINLY NOT BAD FOR TPI



http://www.hotrod.com/how-to/engine/130 ... mparisons/




http://www.academia.edu/4839777/Intake_ ... d_Dynamics



















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