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post #1 of 26 (permalink) Old 11-19-2012, 11:02 AM Thread Starter
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Edelbrock Performer 750 Carburetor

I have a 1980 Corvette with an L48 engine and a TH350 transmission. I would like to install and Edelbrock Performer manifold (part no.2101) and an Edledbrock Perfomer 750 carburetor (part no. 1407). Will the factory accelerator linkage hook to this carbutetor or will modifications need to be made?
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post #2 of 26 (permalink) Old 11-19-2012, 02:17 PM
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post #3 of 26 (permalink) Old 11-19-2012, 03:43 PM
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750 CFM is more than that L48 needs ..it would probably run better with something in the 600-670 CFM range
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post #4 of 26 (permalink) Old 11-20-2012, 05:06 AM
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Correctly Sizing A Carburetor For Street Use

Quote:
Originally Posted by camarocrazy28 View Post
I have a 1980 Corvette with an L48 engine and a TH350 transmission. I would like to install and Edelbrock Performer manifold (part no.2101) and an Edledbrock Perfomer 750 carburetor (part no. 1407). Will the factory accelerator linkage hook to this carbutetor or will modifications need to be made?

For starters you would be making a huge mistake to put a 750 cfm carburetor on an L48 because it is such a weak engine that operates at a very low rpm.

A 350" engine running at 100% volumetric efficiency can only swallow 608 cfm at 6000 rpm. About the only way you can achieve 100% volumetric efficiency is with a tunnel ram, a very long duration cam, and running open long-tube hedders at engine speeds of over 6000 rpm. Most street engines operate at about 75% volumetric efficiency but some high-performance engines can reach 80% to 85% with long duration camshafts, high-rise intake manifolds, and low-restriction exhausts. But even then the 80-85% efficiency comes at the 6000 to 6500 rpm levels; levels far above what your L48 operates at.

With it's "emission" camshaft and small-port cylinder heads your L48 will only make about 75% volumetric efficiency so you start by taking that 608 cfm and multiplying it by .75 which equals 456 cfm. Then as your L48 will only spin 5000 rpm for a very brief time in 1st and 2nd gears multiply that 456 cfm by 5/6 (or 83%) and that equals 378 cfm.

Sorry but the math doesn't lie as 378 cfm is the real-world amount your engine can swallow at it's fastest rpm. So I suggest buying the little 500 cfm version as that would still be big enough to handle a better cam if you ever decide to go that way.

As your L48 is street driven and has high rear end gears I would suggest the 500 cfm #1801 Edelbrock as it has an electric choke and is an "AVS" (Air Valve Secondary) so the secondaries will only open when the air demand is high enough for them to open. With an air valve secondary your engine can never bog under a full throttle as it operates under the same principal as the very successful Rochester QuadraJet. Which brings up a point and that is why do you want to replace your present Quadrajet when it is one of the very best carburetors ever made? With it's very small primaries and huge AVS secondaries the QuadraJet will work very well on the little 6-cylinders all the way up to the big 500" Cadillacs as it'll flow 800 cfm (if needed).

Last edited by toobroketoretire; 11-20-2012 at 06:43 AM.
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post #5 of 26 (permalink) Old 11-20-2012, 06:52 AM
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When you're contemplating changing carburetors I suggest visiting Holley's website and follow their formula which asks you how big your engine is, what maximum rpm will it be operated at, and what volumetric efficiency it has. The results are very sobering to say the least as the recommended size ends up being a LOT smaller than you ever expected.

I'm running a 750 Holley (#3310-2) on my cammed and high-rise 454" and even then it's too big as it'll only swallow 750 cfm once it exceeds 5500 rpm; an rpm that my engine never reaches as it makes it's shifts at 4800-5000 rpm.
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post #6 of 26 (permalink) Old 11-20-2012, 07:54 PM
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There are lots of opinions out there just wondering why you want to change intake and carb? Q jets are very good carbs but difficult for some folks to build and or tune you can get decent mileage and performance from them. CFM range from 600 to 870 or so, Holley is very easy to tune and set up and build they have very good performance but economy will be less than a similar sized q jet. Personally I dis like the edelbrocks/AFB, They can have outstanding performance but setup is harder than a holley and require much more attention on daily drivers. primary metering is held by vacuum on metering rods through a piston setup which can carbon up causing it to run rich at idle and low rpm. Or lean up high depending where the piston gets stuck. but there are folks who have great success with them. If you are not planning on upgrading cam, exhaust, maybe heads why change carb and intake? sit down and plan your mods, where do you want the vehicle to be/do. Daily driver, auto cross, street strip or all out race, then plan mods. Personally I feel I get more from a good exhaust on a stock or mild engine than carb and intake. Again just an opinion, what do the rest of yall think?
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post #7 of 26 (permalink) Old 11-21-2012, 02:52 AM
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I agree, a good true dual exhaust/hi-flow mufflers would be money well spent.. and work well if future mods are planned ..and like I mentioned earlier, the 750CFM will not improve performance of an L48
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post #8 of 26 (permalink) Old 11-21-2012, 02:09 PM
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Quote:
Originally Posted by camarocrazy28 View Post
I have a 1980 Corvette with an L48 engine and a TH350 transmission. I would like to install and Edelbrock Performer manifold (part no.2101) and an Edledbrock Perfomer 750 carburetor (part no. 1407). Will the factory accelerator linkage hook to this carbutetor or will modifications need to be made?
What carburetor do you have on the engine now?
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post #9 of 26 (permalink) Old 11-21-2012, 05:18 PM Thread Starter
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Quote:
Originally Posted by toobroketoretire View Post
For starters you would be making a huge mistake to put a 750 cfm carburetor on an L48 because it is such a weak engine that operates at a very low rpm.

A 350" engine running at 100% volumetric efficiency can only swallow 608 cfm at 6000 rpm. About the only way you can achieve 100% volumetric efficiency is with a tunnel ram, a very long duration cam, and running open long-tube hedders at engine speeds of over 6000 rpm. Most street engines operate at about 75% volumetric efficiency but some high-performance engines can reach 80% to 85% with long duration camshafts, high-rise intake manifolds, and low-restriction exhausts. But even then the 80-85% efficiency comes at the 6000 to 6500 rpm levels; levels far above what your L48 operates at.

With it's "emission" camshaft and small-port cylinder heads your L48 will only make about 75% volumetric efficiency so you start by taking that 608 cfm and multiplying it by .75 which equals 456 cfm. Then as your L48 will only spin 5000 rpm for a very brief time in 1st and 2nd gears multiply that 456 cfm by 5/6 (or 83%) and that equals 378 cfm.

Sorry but the math doesn't lie as 378 cfm is the real-world amount your engine can swallow at it's fastest rpm. So I suggest buying the little 500 cfm version as that would still be big enough to handle a better cam if you ever decide to go that way.

As your L48 is street driven and has high rear end gears I would suggest the 500 cfm #1801 Edelbrock as it has an electric choke and is an "AVS" (Air Valve Secondary) so the secondaries will only open when the air demand is high enough for them to open. With an air valve secondary your engine can never bog under a full throttle as it operates under the same principal as the very successful Rochester QuadraJet. Which brings up a point and that is why do you want to replace your present Quadrajet when it is one of the very best carburetors ever made? With it's very small primaries and huge AVS secondaries the QuadraJet will work very well on the little 6-cylinders all the way up to the big 500" Cadillacs as it'll flow 800 cfm (if needed).
My L48 has significant upgrades to the camshaft, heads, and rotating assembly. The company that performed these modifications dyno'd the engine with long tube headers, an Edelbrock Perfomer intake manifold and a 750 Edelbrock Perfomer carburetor. Long tube headers have already been installed. Future plans include Hooker headers and side pipes. The current carburetor is a 670Holley. Current manifold is stock. The camshaft has considerable duration and overlap. Since the cam has overlap, vacuum at idle is very low. I understand that the dual plane manifold will help with my vacuum problem and will flow much better than stock. As for the 750 carburetor, I happened to have one on another car. Seems as though everyone I ask about the carburetor has a difference of opinion. Some say it's probably too much and others say it seems about right. Will the 670 bolt to this manifold or will I need an adaptor plate.
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post #10 of 26 (permalink) Old 11-21-2012, 07:14 PM
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theres a difference of opinion because you left out that important info in your first post.. you simply stated L48..we all assumed "stock" ..... the Dual plane manifold will improve low -mid-range performance but will not improve low idle vacuum much.. how much vacuum at idle do you have now?it takes 10-12 inhg to operate brake booster.. also the Dual plane will allow for slightly bigger CFM carb, because it increases velocity at low speeds.... what did the engine dyno? ... the stock manifold is spreadbore type, but that Edelbrock manifold is made to take either spreadbore or squarebore carbs,no adapter necessary...what are the cam specs? if its as big as you say, you might benefit more from an Air-Gap or even an RPM Air -Gap manifold

Last edited by fishslayer143@yahoo.com; 11-21-2012 at 07:17 PM.
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