carb choice options

4

4doorscooter

Active Member
Hey guys as some of you may know I am in the process of a cam and vortec head swap on my 355. At the moment I have an edelbrock performer 600cfm carb and it seems to work great at the moment but I am curious as to what you all think of edelbrock carburetors. Do you think I have any power to be gained going to a holley carb and possibly upping the cfm to 650 instead of 600?
 
With a Holley carb, you can adjust EVERYTHING. And that is where most people get into trouble.
They mess with circuits in those carbs that don't need to be touched. Mostly because they can't tune
an engine or understand how a carb works. Run the Edelbrock and see if it does the job first.
You can't just put a larger carb on an engine and expect to make more power. The only way that is
true is if the carb you are replacing was a restriction to begin with.
 
Ive generally had very good results with edelbrock carbs , but mostly when used in pairs on dual quad applications
edl-2025_w.jpg

ID certainly point out that a common 4 barrel carbs rated flow is meassured on a standard industry vacuum reading of 1.5" or mercury , and a change in vacuum changes the effective air flow!
think about that....
that single 600 cfm rated carburetor , you were using ,might see 17 inches of plenum vacume on a rpm air gap single carb intake!
put the same carb, on the same engine, with an identical second carb, bolted on a dual quad manifold, and youve effectively doubled the venturie surface area, effectively reducing the plenum vacuum at W.O.T. so theres no question that the carbs will need to be re-tuned from the way they were set-up to function correctly

edlb-7561v.jpg

edl-7525.jpg

GET A FUEL PRESSURE GAUGE AND MEASURE DON,T GUESS
how can you possibly set up your fuel system unless you know the pressure and flow rates required and what currently exist's
vgauge.gif


READ LINKS

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-regulators.635/

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

http://garage.grumpysperformance.co...ss-fuel-pressure-regulators.12776/#post-65998

http://wallaceracing.com/intakecfm.php

http://www.wallaceracing.com/runnertorquecalc.php
http://garage.grumpysperformance.co...recting-a-rich-edelbrock-carb.1820/#post-4706

http://garage.grumpysperformance.com/index.php?threads/dual-quad.11867/#post-56263

http://garage.grumpysperformance.com/index.php?threads/options-on-dual-quads.11047/

http://garage.grumpysperformance.com/index.php?threads/dual-quads.444/#post-36004
 
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I love my edelbrocks got 2 of them easy to tune run great out of the box. Holley is more tunable but switching to efi ultimate tuning with the right controller but gets expensive for a really good system
 
I tried the Wallace calculator. Using the same set of numbers, I compared dual plane to single plane.
The recommended cfm for single plane came out HIGHER than dual plane. I thought it was the other way.
Someone explain.
 
I like the edelbrock rpm airgap manifold personally from what I have seen from around the ole interweb is that they are giving a close to single plane power on the top end. When I say top end I mean street top end for otherwards within it's advertised rpm range. I know mine pulled real hard up to the upper rpm range without sacrificing my low end. Making a whole combo that works is where it at. Take into account the rear gears and trans gearing. Figure where you want the power and where you need the power. It is a game of compromise high performance street is. Especially with a carb. You are gonna run vortec heads they will be that engines choking point. Yes way better then the old design but not gonna flow like a quality aftermarket street or race head. So take that into consideration. Maybe worked over set of vortecs might flow more but you will sacrifice low end on them. Here is my suggestion make a realistic plan of attack and stick to it you budget needs to be realistic. Grumpy will back me on this build the motor you want the first time use a savings plan or a parts list that is what I do. I have been working on efi for like 2 years now but that is what I wanna run. Been down unrealistic rabbit wholes along the way like the s480 turbo. But that is a sink hole not a rabbit hole would envolve building an 4l80e and a new rear end and everything in between. Pretty much take my car strip it to a shell then build it not in my budget or giving me time to enjoy the car. So that list works like a teather keeps you from go into the deep end while you explore. Complete price lists including gaskets, fluids, Bolts and all the little things you didn't think through add up quick. You own the eddy 600cfm and bet this is a street engine mild performance build. Run it, tune it spend the $160 get an AEM wideband o2 sensor or glow shift has them also but think they are all around the same price. When I first started playing with engines it was amazing what a set of headers an intake and a carb will do if matched to the rpm proper. Add a cam in there and it will make more then the average joe happy.
 
QUOTE "The recommended cfm for single plane came out HIGHER than dual plane. I thought it was the other way.
Someone explain."

read through the linked info here
http://garage.grumpysperformance.com/index.php?threads/carb-intake-test.58/

Its mostly due to the total plenum volume and air speeds entering the port enterance and runner cross sectional areas, single planes tend to have larger and shorter and straiter runner designs, that require larger and more efficient carburetor venturi cross sections,
intake flow is NOT constant, its feed is intermitent and its over very short time duration.
for example at 7000rpm, your intake runner is flowing air intermetently about 260 degrees of rotation, of every 720 degrees, and thats happening (starting and stopping) about 60 plus times A SECOND, the dual plane has a much smaller plenum, becuase its designed to keep air speeds up to maintain the fuel mist suspened in the air flow at much lower average rpms, just keep in mind that the single plane intake design is intended on average to operate about 1500rpm-2000rpm higher , so the plenum volume and average air flow must be higher/larger to maintain the volume the engine requires, and the larger single plenum, of the single plane intake will not be restricting the ports ability to maintain that required flow as much as a much smaller dual plenum of a dual plane intake.
most single plane intakes have less than ideal fuel/air ratio mix characteristics while operating under about 3500 rpm.
remember the intended operational ranges
dual plane intakes generally operate effectively in the 1500rpm-6000rpm power band
single plane designs operate more efficiently in the 3500rpm-7500rpm power band
thats roughly 2000 rpm higher on average

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THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations[/color]
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.circletrack.com/enginetech/1 ... ch_engine/
porting+valve_area.jpg


http://garage.grumpysperformance.co...-calculators-and-basic-math.10705/#post-50173

http://garage.grumpysperformance.co...gine-to-match-the-cam-specs.11764/#post-55571
 
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Thanks. It makes sense. I was under that impression because GM commonly ran larger cfm quadrajets on dual plane manifolds. I read that in one of my SA Design books on SBCs, can't remember which one. I think it was explained that you could get away with using a larger than normal cfm carb on a dual plane intake because of the divided (and 1/2 the size) plenum. The port velocity in each half would be higher (than a single plane), therefore the vacuum signal to the venturi would also be higher. Maybe I got it wrong. When I have time, I will have to reread those books.
 
1960 283 in an Impala. Bone stock with a two barrel carburetor. I believe Chevy says it makes 170 hp. They advertise the 4 barrel at 230 hp.

I was thinking about changing to a four barrel, and dual exhaust. Would there be any performance increase? I could also go with the cam if there would be a benefit. Would consider headers as well.

Not really wanting a hot rod, just a little more zip. It’s a street car, so drivability is important.

I am sure that this topic has been covered at nauseaum here, but I am new to the group. If anyone could point me to a thread that addresses this topic, that would be great.

Thanks!

PS. I know I could just drop 300 hp crate 350 in it. But hey, I prefer to keep the little 283 in it.
Click to expand...




heres the route Id go if it was my car, and yes thats a 650 cfm rated carb, it will function very well on your mild 283 , don,t let someone tell you its going to be vastly over carb size for that engine.
I've seen several people have very good results from these carburetors in similar engine combos, this is a mild upgrade to a stock 283 that will work well with the stock power glide auto transmission.


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http://documents.holley.com/streetdemonarticle.pdf








pressuregag.jpg

https://www.jegs.com/i/Weiand/925/8...MIqvqx4-7k2wIVi8DACh16DQahEAQYAiABEgLyLfD_BwE

https://www.jegs.com/i/Demon-Carburetion/333/1900/10002/-1

http://www.pbm-erson.com/Catalog/Erson/Camshafts/Hydraulic Flat Tappet_E/ERSE110020

  • Cam Type:
    • HYDRAULIC FLAT TAPPET
  • C
  • Duration @ .050:
    • 209/216
  • Duration Advertised:
    • 275/278
  • Gross Lift:
    • .443/.455
  • Lobe Center:
    • 112
  • Make:
    • Chevrolet
  • Part Name:
    • Engine Camshaft
  • RPM Range:
    • 1200-4000

its rather obvious that some of the previous posters, on this web site, don,t fully understand exactly how a vacuum secondary carb, precisely meters air flow based on the engine plenum vacuum.
a vacuum secondary carb matches flow to demand vacuum,a 4 barrel carb is rated at a standard vacuum of 1.5" of mercury, if the vacuum under the carb is lower it flows less, if it higher the increased vacuum causes the carb flow to increase.
theres no debate that the 283 power glide equipped engine will only need about 500 cfm , but a vacuum secondary 650 cfm carb will supply whats required without causing any drive-ability issues if its properly tuned with no down side.
btw the power glide transmission is costing your car some performance.
theres hundreds of thousands of fully functional and easily rebuild-able other G.M. transmissions (many with three gears plus over drive) available rather reasonably in salvage yards all over the country

http://www.hotrod.com/articles/0802phr-how-carburetors-work/

http://4secondsflat.com/Carb_CFM_Calculator.html

http://www.thecarburetorshop.com/Carbshop_carbsizesandCFM.htm

http://www.rasoenterprises.com/engine-technology/40-carburetion/19-carb-flow-rating

http://www.rasoenterprises.com/engine-technology/40-carburetion/18-carb-flow
 
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