Exhaust limits/Carb choice

maw said

The manifold is a Wieand Stealth which is a dual plane similar to an Edelbrock Performer RPM, but with a spread-bore flange.

I have two questions concerning the package:

1) At what point do I saturate a cast iron exhaust manifold set and have to go to tube headers? (The car came with a set of Hooker Comps which have a couple of flattened primaries which could be fixed. I also have a set of 360 A-body cast iron manifolds.)

2) We have both a 750 Thermoquad and a Holley 650 spreadbore double pumper. Which would be the better choice.

Cheers, Mark

Click to expand...

Mark, the Weiand Stealth has a square flange and the Action plus has the spreadbore flange, though through pictures, thats the only difference I can see.
You can keep the exhaust manifolds though the power difference will be noticeable between them when you do swap them over. Search headers here for opinions and been there done that fitting of Super Comps and tti's.

To get more from the manifolds, a longer exhaust timing duration will be needed. I would talk to a cam manufacture and tell him of the manifold useage. The cars that race in the F.A.S.T class run real well with manifolds and use a different cam timing set up unlike I would with headers.
(They also stroke there engines .)

On the carb, the T-Q has certain advantages over the Holley. Smaller primarys for the street for better throttle response and mileage. (Or at least should. Good mileage should be obtainable no matter the carb primary size.) The double booster design is key there. The secondarys are huge @ 2-1/4 for a real powerful kick.
BUT, the tuning parts are a little harder to come by and it can be a trickier carb to set up and set straight than the Holley if your not use to them.

The added CFM of the T-Q may be helpful, but not needed. 650 cfm is enuff to really move a powerful 318. A T-Q though larger has adjustable air door opening size and it's adjustable on when it opens making this carb fine for the 318 as well though it's 100 cfm (or so) larger, it will not be to much.

The bottom line is what ever carb you feel comfortable with is the one for you.