Edelbrock C357 flow capabilities

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Buddha
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

I was considering going to to 4 of the smaller venturi units so the cfm capacity more matched the motor. My thoughts were to avoid the equivalent of putting a dominator on a 283 and the inevitable bog on full throttle at anything lower than 3 or 4 thousand rpm. I might be overthinking it as this isn’t going in a 4,200 pickup with highway gearing. If it does bog, I can always plumb up the VS 57 McCulloch and give it a little low pressure force feeding.
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

3 or 4 of the 435 cfm 2 bbls is not over carbing it at all.
Its a 383. It wants to eat.

Use the right stall converter and gears.
Remember the OD top gear has a profound effect on cutting the cruise rpm of 4.56's.
If you do change rear gears don't go too far down in ratio.
A cammed engine wants to spin even in OD at cruise.

I'd use a built th2004r. Better trans for this.
This trans is lighter weight takes less power to spin
and have better ratios.. 2.74/1.67/1.00/.67
One upgraded it is plenty strong.
Better perf than a 700r4
Custom 245MM high stall lock up converter.

Realise also on the big Dual Plane RPM air gap intake the plenum is split 180° ... 3x 435 2bbl carbs is nothing on this setup.

Look for the big venturi carbs.
This is still a very responsive venturi size.
And the throttles are progressive action.
Last edited by F-BIRD'88 on Thu May 05, 2022 12:36 pm, edited 1 time in total.
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

Once you have got the 2x4 RPM air gap dual quad manifold modified you are free to create carb adapters that bolt on
to get various multi carb configurations.
2x2bbl 3x2bbl rochester ,3x2 holleys 4x2 rochhesters.
Etc.
This is a powerfull street friendly multi carb dual plane intake manifold. The mods are straight forward for anyone with a mill.

I would keep the plenum and the carb adapter top Split.
180° phasing. For sharpest low speed throttle responce.

The small cfm 2bbls are going to leave you wanting...
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

Thanks for the input. I was thinking that 1740 cfm on a small block was grossly over carbing. I do like the idea of once the initial machining is done, then you can make different tops and play around and try different set ups.

The car is currently set up with a 32” tall tire so that, along with the OD of the trans should be okay for anything but long trips. I like to drive hot rods and not Tralee them to events. The exception being taking to the track and beating on it hard. If I were to change transmissions, I would be leaning to a Tremec or Richmond 6 gear. Foot well space is limited in these and having a 3rd pedal is doable just very limited.
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

2bbl carb (@3.0") flow rating X .707 equals the 4bbl carb flow rating @1.5"
Add up your 2bbl carbs cfm flow rating
X .707

Why would you on a cammed up engine want to
drop the gearing with huge 32" tall tires.
With 4.56's the OD gear is actually usefull.
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

I guess because a 383 should not need 1200 or even 900 cfm. 4 or even 3, 435 carbs should be more than adequate.
To answer the other question of why have another chunk for the 9”. You ever drove 300 miles one way with steep gears? It gets kind of monotonous running at 3,000 -3,500 rpm’s for hours. The gear change will come later on, but It has to be substantial enough to make a big enough difference or I won’t go through the trouble to swap it back and forth.
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

With a Th700r4 and 32" tire and 4.56's
@70 mph hiway cruise speed the cruise rpm in
OD is 2340 rpm.
A th2004r. In OD will be 2245 @70 mph.
Better OD better gear ratio spred too.

A 383 that makes good power needs to eat. Choke it down with small cfm carbs and you might as well do a 305.
4x 435 2bbl carbs is just barly enough.

It seems these automotive maths are not your strong suite.
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

Been quite a few years since I did the math on the rpm projection. For some reason I had 3,000 rpm for 70 mph in my head for this setup. I was thinking 75-80 on the turnpike. You’re right 2400 rpm at 70 is very comfortable.
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Re: Edelbrock C357 flow capabilities

Post by PSA »

Maybe talk to these guys, I believe they have posted results on different socialmedia platforms.
http://www.autotrendefi.com/efi-2g.html

I believe a 2X4 was tested by Richard Holdener and it was down on power everywhere compared to a regular dual plane. I guess some runners are just too short and there's little flow gain to make up for it anywhere else.
But please double check that, and I believe it might have been on a LS engine as well.
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

You need to define how you will use this car, what engine rpm you want to hiway cruise at in OD.
Do you want a "mild" engine?
Do you want low speed torque and easy "drivability"
Are you more of a "cruiser" or a "racer"
Do you want a relative near stock like low stall torque converter.. OEM like rpm range, low rpm at cruise, OEM like "drivability"

Engine horsepower. (be realistic)
The Eddy C357 intake was designed and intended
for the engine cylinder heads and target horsepower and usable rpm range of engines of the day.

This is NOT a 500 horsepower intake manifold.

Think 325-350-400 BHP.
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Re: Edelbrock C357 flow capabilities

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There are a few nostalgia runs that I go to for at drag strips. In order to compete for the “cup”, you have to drive your car at least 150 miles, then run. One of these is about 200 miles away. Car needs to run in the high nines preferably or at least low 10’s to be competitive. While going with a BBC would make the goal easier, I’d like to stay away from the weight and additional headaches of trying to keep a big block cool in traffic with a small radiator. It’s hard enough with a 406, and that is after going with a very high cfm electric fan and the fore and aft bypass plumbing on the intake.
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Re: Edelbrock C357 flow capabilities

Post by F-BIRD'88 »

High 9. low 10's. 1/4 mile. you gonna need a hell of a tail wind.
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Re: Edelbrock C357 flow capabilities

Post by Buddha »

550-575 no tailwind required.
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Re: Edelbrock C357 flow capabilities

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Even without getting the specific flow numbers I was originally looking for, those responding have lead me to conclude that this tri-power setup isn’t going to produce the power I’d like. Thanks, as that was goal of the thread I’ll just have to go a different route or just spray it to make the numbers. I really don’t want to spray, the little coupes don’t have much trunk room with the fuel and battery back there. I suspect F-Bird is pretty close in estimating that it’s a 3-400 hp induction system, no matter what you stick it on top of.
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