Edelbrock C357 flow capabilities

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Edelbrock C357 flow capabilities

Post by Buddha »

Does anyone have anything on flow capability of the small block Chevy tri-power intake? I’m contemplating buying some aluminum heads for a 383 small block and don’t want to waste my money if the manifold and carbs won’t flow enough to make a big difference.
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Re: Edelbrock C357 flow capabilities

Post by rebelrouser »

I think you may be in uncharted waters. The only advice I can give is to have the manifold flowed. Make sure they block off all the runners but the one you are flowing. Then compare with published flow numbers on the heads you are considering Never ported one of those manifolds but I have done some OEM dual plane cast iron ones for limited puling truck engines with some success. And just from looking at photos of it, looks like some improvements could be made. And while that manifold may be a bottle neck, better flowing heads will help, just how much is the question.
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

This manifold is relative low rise type with relative small port cross sectional area. The plenum volume is modest for max hp.
You will make more power and torque by starting with a Dual Quad RPM air gap manifold (2x4 carbs) and then modifying the carb flange to accept a custom 3x 2bbl carb adapter. (3x holley 2Bbbls)
Higher high rise carb height. Generous plenum volume.
(can be 180° split /full plenum divider. OR can be reduced plenum divider for R/L plenum sharing.)

Larger port cross sectional area and flow than C-357.
Increased total carb cfm flow.

https://www.edelbrock.com/pub/media/cat ... 5_v2_2.jpg

https://www.speedwaymotors.com/_next/im ... w=850&q=75
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

Thanks for the advice. I didn’t want to go through the trouble and expense of doing a good set of heads and roller to find that I basically have a good looking restrictor plate
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

Well, the top picture is relevant, disregard the rest
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Re: Edelbrock C357 flow capabilities

Post by Tom68 »

No experience, but 3 200 hp carbies won't be the restriction.
Manifold at a guess would be good for 400 to 450 hp on a hard sucking 383 ??
So I guess you'd need 225 cfm capable heads.
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

I was looking at the AFR Eliminators, or similar heads. Aesthetics are important on this build more important than high horsepower. I would like to find a setup that keeps the 50’s - 60’s look while delivering power.

Weight is #2750 with driver, 4.56 9” going through a 700R. Will probably go to a 3.50 or 3.25 gear for long hauls. Would like to do better than 400 or 450.
I was hoping someone here had some experience with this manifold and some flow numbers. There are a few carb guys or possibly Edelbrock may have something.
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Re: Edelbrock C357 flow capabilities

Post by Tom68 »

Might have been a magazine comparison when the c3bx came out, edelbrock may have even done one. But that's 1970 odd and would have been with fuellie heads.

I'm betting there will be a lot of grinding and maybe some welding if you're looking for over 500.

Dual plane, so if you can get the runners big enough open carb spacers may help up top.

You really need dyno numbers, cfm isn't going to cover the crazy pressure waves this manifold will have.
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

I just got off of the phone with Edelbrock. Apparently they didn’t own a flow bench until they got into the head business. Millions of manifolds sold, designed on paper, out the door. They apparently let the consumers do the real testing and the ones that didn’t perform were quietly discontinued. It seems strange to me that a company whose primary business was performance manifolds, and a well respected one at that, was just winging it when it came to what worked and what didn’t. Since the car is an open hooded highboy coupe, I suppose I can play around with some 2-3” open plenum spacers and see if that seems to help, though I fully suspect that this setup is not going to fulfill the power level I’m looking for.
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Re: Edelbrock C357 flow capabilities

Post by Steve Salesky »

What did Joe Sherman who used to work for Edelbrock back then say? "An intake manifold is something to hold the carb. up"
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

I called back to another tech. He said he would look for some numbers. I was going to ask him if they could flow one off the shelf. You know, because now they have a flow bench or three AND they still sell the manifold. I know it’s old tech and they make the money on heads and blowers and shiny stuff for LS and new hemi and Coyote platforms, I’ll more than likely go to a tunnel ram if I want up the power
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

Others already go with a tunnel ram and a custom 3x2bbl plenum top.
3x 435 cfm (@3.0") rochesters flow the same cfm (@1.5") as a 922 cfm 4 bbl carb does.

The big 435 cfm rochesters have a 1-⅜" venturi and 1-11/16" throttle bores. The largest versions of the rochester 2 bbl carbs.
This will make good power and torque.
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

Well, I never heard back from the Edelbrock technician, not that I really expected to. Made a call to a tri-power and all around very experienced carburetor restorer. He deals mostly in OEM setups and as much as he loves tri-power setups, told me it would probably be a disappointment to make real power with even a large small block.
My thoughts are that if I’m going to go through all of the trouble of adapting or outright building a tunnel ram top, then I’ll do it so the thing should run right. I’m thinking 4 of the small 2 barrels and we won’t have any of the odd cylinder to barrel ratios going on. It will be something different but hopefully function well.
Thanks for your input
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

4 of the big venturi 435 cfm 2bbls will flow
1230 cfm @ 1.5" You can do pretty good with this on a healthy street motor..

Others have cut off the top carb flanges and allum welded a custom 3x or 4x. 2bbl carb mounting flange
on the top of the plenum.. The weiand Hi Ram is the easiest to work. re-work. The Edelbrock street tunnel ram is a bit more powerfull..

Do not discount modifying the plenum carb base
and adding a adapter carb plate for 3X 2bbls or 4x 2bbl carbs on a Edelbrock Dual Quad RPM air gap manifold.
It involves custom maching the carb flange and adding a custom made carb top. It can bolt together.
It will make great S/S power on a hot street motor

If you want horsepower you want to use the larger venturi 435cfm carbs on all these, in either 3x or 4X carb form. Let it eat.
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Re: Edelbrock C357 flow capabilities

Post by Tom68 »

Six little 2 barrels on a little motor, 60's style.
Seems to do alright, must have been fairly drivable, a few blokes down here used them in what we called Modified Sprintcars back in the day.
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