[Beaverboy]

I'd think you wouldn't notice too much loss of torque with the GT header.. if any at all. The small shrouded valves in the LX head are going to keep the low RPM tumble and high flow velocities. My best guess is that the header may broaden the torque curve just a little further up the RPM range without much lower end loss at all. Just don't port out the header or exhaust ports :wink:

I'm with Jugg, keep to a 2.25" (or 2.0") diameter piping and you'll end up maximizing hp and torque.

Remember, you can have the best exhaust in the world, but if the intake can't flow enough to match it you won't get anywhere. (of course, you're lucky enough to have the larger MAF already :x )

 

[Beaverboy]

Then get a loud intake and have a muffler shop install a large baffled turbo muffler.

 

[Beaverboy]

Just don't port out the header or exhaust ports

Why not? isn't it supposed to increase the flow in the exhaust system? always though it was a great improvement to do this kind of work on your system....

would be nice if you could clarify this for me Tanks mec

I'll clarify.. I said that kinda wrong. What I should have said was, "Just don't port out the header or port match the exhaust ports."

In other words, the GT header primaries are probably plenty big enough for the SEFI 1.9L from the 2nd gen, and you're probably only going to be shooting yourself in the foot if you were to try to make them any larger. I'd imagine a little honing (polishing) wouldn't hurt though.

Yes, porting the heads (and in this case, installing larger valves and cam) is a great idea.. port matching the exhaust ports to the header is not. Having the exhaust ports smaller than the primaries has shown to help on the dyno. That's what I meant to say

 

[Beaverboy]

Yeah, port matching on the way in is good.. keeps the flow nice and smooth (sometimes a tiny lip to spill over will help).

I've read that the spill-over from the exhaust port to the primaries may help to block reverse pulses and give them something to bounce back off of. It's apparently better to leave the ledge at the outside of the curve for some reason. Smoothing out flow on the inside of the curve seems to be an over-ridding theme in head design. (I've been reading A. Graham Bell - Four-Stroke Performance Tuning in Theory and Practice the past week.. interesting stuff)

 

[Beaverboy]

Check out the article: Build Your Own Exhaust

Some great info there.

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Of note.. the pipe diameters listed for each approx. engine size are not for max power, they're for best midrange and low end for street cars. Go up one size if you want max top end power.

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