428" Header Size Recommendation
428" Header Size Recommendation I am building a N/A 428" motor 4.130/4.0" with CNC ported aftermarket WCCH LS7 heads. Cam is custom EPS 631/640 226/242 115+3 LSA. Ported factory LS7 manifold. Car is 3850# dry. 5_speed manual trans. I have choice of 1 7/8, 1 7/8-2" stepped or 2" primaries. I would like some advice. Thanks.
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we've done some back to back testing on header sizes. It seems that the bigger tubes do not hurt the low end performance-but def helps up top. I would vote 2'' myself.
On a 4.125" bore I recommend a 2" header for maximum performance, though the stepped headers will probably make the most low end torque if that is what you're concerned about.
I agree. And that split is HUGE. Maybe it is supposed to be a 236/242 not a 226/242. Even so, the 236 with a 115LSA is small. My 421 motor with ported 243s runs a 239/247 with a 110LSA +2 (Single plane intake is the reason for the tight LSA). I would think that motor with worked LS7 heads would want a 246/250 at minimum........
I have had a lot of traditional musclecars with big cams, overlap, and all the characteristics that go along with it. This being my first LS motor, I wanted for once to show a little restraint in the cam department. I look at the LS different than the other motors I've had. I really wanted something that has big power, is really driveable, and did not have a huge lopey idle. That is what I have have had each time before, and even though my 466 Pontiac was EFI'd, it still was a little too over the top. I contacted Geoff at EPS because I did not want to guess on the cam. I told him I wanted an easy 600 HP, wanted a little lope to it, but not the tight LSA and overlap I had before. The 226/242 is correct, and necessary on the square port heads. The real important part of the equation was that I decided that I wanted to run catalytic convertors. I have grown tired of the smelly musclecar thing, and the big inch LS is the perfect way for me to make that much power, and still be able to get rid of the smell. At first I thought the cam was small, but after thinking about it and sticking to the plan, I did not second guess Geoff. He knows what he's doing. Also my car is heavy, so I need good low end power. I also did not want this motor to need to be revved to 7k. I told him 6500 is fine. I will be starting a build thread on this soon, and will post all of my dyno sessions, so hopefully everything will work well together. Thanks for the interest and advice.
Last edited by Later-A-body; Sep 29, 2011 at 01:16 AM.
What you do with the car, makes the decision important.
Drag car- 2"
Street car 13/4 or 1 7/8.
With a stock LS7 intake, and stock LS7 castings, 1 3/4 will give much more area under the curve, below 4k. Above 4K, the 1 7/8 will make 10 more rwhp but feel significantly sluggish. The trend is that bigger is better, but that depends on the use.
Yes, I said 1 3/4 with a proper merge collector and full 3" exhaust on an LS7. We make the most powerful headers on the planet for LS7s C6 Z06s. Lots of dyno time and testing.
Drag car- 2"
Street car 13/4 or 1 7/8.
With a stock LS7 intake, and stock LS7 castings, 1 3/4 will give much more area under the curve, below 4k. Above 4K, the 1 7/8 will make 10 more rwhp but feel significantly sluggish. The trend is that bigger is better, but that depends on the use.
Yes, I said 1 3/4 with a proper merge collector and full 3" exhaust on an LS7. We make the most powerful headers on the planet for LS7s C6 Z06s. Lots of dyno time and testing.