SBC Engine build

[Jblake]

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

[BigTruckDriver]

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

[techinspector1]

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.

[Dave Severson]

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......

[tango]

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 .

[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....

[tango]

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 .

[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

[mopar34]

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

[erik erikson]

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.

[shop tom]

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