Thread: SBC Engine build

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I need some help in determining which heads would be best for a 355 qu. in. Chevy engine. I want to use AFR heads but I am having difficulty in chosing between the 180 cc 195. I am planning on using a forged crank and also forged aluminum pistons, compression ratio 9.5 to 1. I will be using a comp cams hydrolic roller XE276HR which has a duration of 224 on the intake and 230 on the exhaust. Intake manifold is a dual plane.
This engine will be used in a 32 Ford Roadster with a Tremec 5 speed transmission and 3.73 rear end gears. The car will be used almost exclusively on the street. I could also use some suggestions on which carburator. I am contemplating using a Holley double pumper. I am not sure which CFM would be best.
Any suggestions would be appreciated. Joe

If its a street engine the smaller runner heads would probably be best.

I use a formula of (CID x .5 = head port volume) for a street motor, so 355 x .5 = 177.5 cc's. I'd choose the 180's.

You're using a dual plane manifold that will sign off at 5,500.
You're using a cam that will sign off at 5,500.
So, it makes no sense to use a carburetor that flows more than the motor can use. Being generous and saying the motor will ingest and use air and fuel at a 100% efficiency, 5500 x 355 divided by 3456 = 564 CFM. Being more realistic and saying the motor will operate at 90% efficiency, 5500 x 355 divided by 3456 x .9 = 508 CFM.

You can use a double pumper if you want to, but with gas prices being what they are and realizing that you are not building a world beater anyway, so it shouldn't need a double pumper would make me seriously consider a 600 with vacuum secondaries, no matter whose name is on the outside of the carb.

yuppers, not a lot of reason to put 8,000 rpm parts on a 4500 rpm engine... A nice 600 CFM vacuum secondary would work great.... With that 5th gear overdrive and a 3.30 to 3.50 rear gear should be a nice setup... The Tremec trannies are plenty low ratio enough to carry a good highway gear......

First thing the way that 355 is built even with the 180 heads . It will not Sign off at 5500 RPMs . And they make Dual Plane intakes that can pull all the way to 6800 RPMs . And yes the 600 Holley V/S will not deliver enough air or Fuel to a 355 Built Like that . You said you want to build this for street . Go with a smaller camshaft even Vortec heads a mild dual plane intake and a Holley 670 V/S Avenger . Also run a 355 gear the first gear in the Tremec is big enough . Now you will have a street engine that will have more Torque and get better MPG then that other build .

Just remember that regardless of brand or size the two most common mistakes on an engine build for the street is too much cam and too much carb.... With $4.00 a gallon coming soon, if you're planning on a lot of cruizin' miles, leave the race parts for the race cars and stick with a performance level you can afford to drive....

Originally Posted by Dave Severson

Just remember that regardless of brand or size the two most common mistakes on an engine build for the street is too much cam and too much carb.... With $4.00 a gallon coming soon, if you're planning on a lot of cruizin' miles, leave the race parts for the race cars and stick with a performance level you can afford to drive....

Very well said . And you can build a Street car that can perform and get good MPG .

Thanks to everyone for all your help. I will plan to use the 180 heads and maybe back off a little on the cam selection and maybe think about a Holley Street Avenger. I think they make one which is 570 cfm. Thanks again. Joe

JBlake, with your last comment I think you are headed in the right direction.

Originally Posted by Jblake

Thanks to everyone for all your help. I will plan to use the 180 heads and maybe back off a little on the cam selection and maybe think about a Holley Street Avenger. I think they make one which is 570 cfm. Thanks again. Joe

Have you been to AFR's web site?
If not I would check it out.

I'd consider bumping the compression ratio up to at least 10:1. The aluminum heads will have the effect of reducing the compression ratio to less than 9:1. because of their thermal efficiency.

tom