[Tim Corcoran]

I would say that you made so many changes when you changed heads that is difficult to know if or how much low end to torque you may have lost due to the heads. If you had a before and after dyno sheet that may tell you more. You went to large tube headers, and a different, bigger cam, that 230/230 may be a dog of a cam for your new combo. That cam may need more compression to work well. Since you went from iron to aluminum heads with only a .4 increased in compression in a way your compression went down. I was running 1-5/8 headers on a 474ci motor and it was a torque monster. Those large tube headers may be slowing down exhaust velocity and your not pulling in the intake charge as hard and hurting VE. The complete combo is the key, everything working together, sometimes it happens by accident. When you put together an untested combo it's an experiment and sometimes it doesn't all work together as well as expected. I would not blame the heads, those heads can give you plenty of low end torque with the right parts to support it.

[Firebob]

Tim, you are right about making too many changes at the same time that now it's hard to tell if it was any one thing or a combination of several different things. I usually try to avoid it by making smaller changes and then testing but it just kind of happened this way and besides I didn't want to tear it apart too many times as some of the changes were fairly major.

Paul, I didn't mean to sound like I was calling you on it. I didn't really pay much attention to how much stroke was added on your test motor. Usually when I see someone has gone to the trouble to stroke a motor it's not done in a minor way. Like 400s turn into 460 somethings or 455s turned into 474s, that sort of thing.

I guess this will just be one of those things that I will have to play with and see if I can make it better little by little. If not, I'll build the 455 and start all over.

[Formulajones]

I agree with Tim, that with so many changes made (cam/headers/compression) you can't really blame cylinder head intake port size.

Frankly, everyone calls the round port Edelbrock the "big" port heads when they are only a 215cc intake runner, yet their D-port head measures 204cc. There isn't enough difference there to sway me one way or the other. The only problem with the round ports are the headers on the market, smallest being 1 7/8. That's a bit on the large side for a street destined 400. Your only other option would have been a set of ram air manifolds, and would likely have been the same price (or cheaper) than the headers you bought depending on the brand and coatings. Ram air manifolds however would make me want a different camshaft choice. Depending on your dynamic compression currently, camshaft timing might be something you may play with anyway if you've lost any of your low speed cylinder pressure. Have you checked your cranking compression or know what it used to be to compare to?

Either way, there are too many 200cc+ heads out there on the street and track on even smaller engines than your 400 that make good usable power.

[68azbird]

With a full exhaust system the header tube size is a non issue.

[Firebob]

Well you guys have to remember too that these are probably a bit more than 215cc runners. Out of the box Edel says these heads flowed 265 or so and these are in the 295 range. There has been some porting done to them. I wonder if I would see any change in the low end by advancing the cam a couple degrees?

Tim, I agree. Finding the right combo of parts that work well together is my current quest. Also finding them before I go broke(again) is the issue.

[gtofreek]

Originally Posted by Firebob

Tim, you are right about making too many changes at the same time that now it's hard to tell if it was any one thing or a combination of several different things. I usually try to avoid it by making smaller changes and then testing but it just kind of happened this way and besides I didn't want to tear it apart too many times as some of the changes were fairly major.

Paul, I didn't mean to sound like I was calling you on it. I didn't really pay much attention to how much stroke was added on your test motor. Usually when I see someone has gone to the trouble to stroke a motor it's not done in a minor way. Like 400s turn into 460 somethings or 455s turned into 474s, that sort of thing.

I guess this will just be one of those things that I will have to play with and see if I can make it better little by little. If not, I'll build the 455 and start all over.

No problem, I just stroked it the .015" since I was grinding the crank .050" under for BB Chevy rods, and I wanted to take full advantage of the cubic inch rule of 410". Ours came in at 409.39".

[Skip Fix]

Originally Posted by 68azbird

With a full exhaust system the header tube size is a non issue.

I disagree my RAIV 400 running through exhaust even a 3" head pipe and 3" 2 chamber flowmaster system did much better with eth smaller headers than the big headers 0.2 seconds and 2 mph.

Hedman makes a 1 3/4 for second gen F body and GTOs-fit was terrible and redid 2 tubes each side but it made a considerable difference on that motor.

[Firebob]

Some of those mag test samples don't make me feel any better. The best time I could lay down before the changes was a 13.8@98mph(car and me go 3900lbs w/A/C) with aweful traction issues. Had one bystander tell me I was spinning about halfway down the track. I suppose with a set of ET Streets it would've done much better. Not sure what it would do now. I've got an appt on the dyno next week to see where the differences show up on paper from before. Maybe I'll make a run at the local grudge drags to add to my homework.