can you run doug headers with an a/c on a 68' 400? they seem to exclude a/c cars in there instalation problem area. just figured i would ask. thanks tim

hello

If you don't get an answer quickly you can call their tech line and a real person will pick up and answer your question.

I have Dougs on my 68 - 428 with air. What are your concerns?

Motor goes on the dyno the 12th. We are going to start with my long branches and tune there. The shop has a set of headers, the plan then is to get a couple pulls with the headers as well. To see what happens with the numbers. My builder thinks we will get up to 50 Hp. More. When you think how much 50hp. Can cost to get in other ways. It hard not to look at going that way at this point.

I will be waiting to see the results. I bet there will not be a big difference between the two. I didn't see the big gain when I made the change. Keep us posted.

With out changing the heads to isolate the center exhaust ports there will not be much difference.

The power curve with headers will be at a higher rpm.

If you are talking about running your motor on a stand dyno (outside of the car) then there will be practically no difference at all because there is no exhaust system per say.

very curios to see your results, if you are running a cam with less lobe seperation (more overlap) the scavenge effect of the headers will probably give you quite a bit more power (50 hp does seem like a lot). with wide lobe seperation like factory cams 113 plus degrees, you might not see anything with the headers. are you running factory cast d ports? what cam? I once read about a test done with a stock 76 455, the only change they made to the engine was to put headers on in place of the factory "log style manifolds" and it made no significant difference to the engine because the stock cam was too small to make the headers work

255cfm SD ported head, 4.21 stroke forged crank, 224/236 @.050 just .530 lift,tighter lsa' full roller. built q-jet, 0 decked, custom pistons 9.2;1. tuned dist.. gasket ported stock intake, msd ignition. long branches. it's a driver and a conv.. it's pretty close the the pure poncho mule engine in the mag.

very sweet!