What kind of power diff will there be from a mid to a LT header

 

Basically the same sense there the same size, the midlength will produce more mid rpm power and the longtubes high rpm power.

 

the LTs will create more power everywhere, for an LT1 there is a large difference between mids and LTs.

 

Longtubes will have more low end torque.

 

Yeah why does everyone say LT's hurt bottom end & increase top end, I always thought its the other way around, the longer the primary, the more pressure you have to have low end power, when the the exhaust gas hit the collector it creates a low pressure side scavanging the exhaust out of the primary which is good for HIGH RPM, while LT's have longer primaries so the scavanging effect is delayed which hurts top end.

I'm not good at explaining it but basicly, the shorter the primaries the faster the scavanging which is good for High rpm to speed up exhaust flow, & not for low rpm since you need back pressure which is done with a longer primary like a long tube header so there is always exhaust to create bottom end power.

Reason we might see benifit with long tubes is because most people don't rev very high, if we were to rev to 9k rpm, you'd see major benifits in shorties, I bet after 6krpm to 7krpm shorties are starting to overtake the long tubes.

There may be more to it, I'm not expert in this but it makes sense.

 

Hey Bumker,
how dop you like your set up and the 847 cam, what are your power numbers, i have the same set up as you well i will now

 

The way I understand it, it relates to the pulse wavelength of the exhaust impulses in the cylinders. At lower RPMs the wavelength is quite long. The idea is to match the primary length to the wavelength that you want to tune for maximum torque. That wavelength corresponds to a specific RPM. Therefore, longtubes on an LT1 may be tuned for maximum torque at say, 2500 rpms. But the fact that they have larger primary tube diameter also allows them to produce torque at higher RPMs. I was under the impression that scavenging was more important at lower RPMs, since at higher RPMs it relied mostly on the momentum of the air. Besides, don't most performance camshafts open the exhaust valve up to 60 degrees Before BDC? (30 Degrees ATDC) I thought this was to minimize pumping losses.

 

Anyone have any dyno number from going mid to full. what kind of power, % would there be
thx

 

Yeah i would like to see some dyno #'s also. But it would also depend on what sent of mids you had and what set of lt's you went to. Because some are better then others.

 

a while back someone did that and they said the as&m mids made as longtubes

i can't remember the name

 

Whats the diference?

I agree with the other statements though. Shorter primaries for higher RPM, holding diameter constant of course. There is a
calculator for that here on cz28.

Steve40,
The someone your recalling may have been Fred speaking about George Baxters car. He had a high HP high reving engine so the shorter primarys where probably closer to the optimum length for his setup then the longtubes. It's not a perfect comparison for the majority of bolt on LT1s not spinning as high. BUT i do agree that the difference is not nearly as much as some people claim without any experience with both. I chose midlengths for my car because i didn't feel i was giving up that much.

-brent

 

that would be the one,

i too did go with as&m's, i have no problems with them and just for a bolt on, i feel it runs fairly strong

guess it comes down to what kind of deal you can find

 

I do know this...Everyone told me my car wouldn't make any power with MAC 1 5/8" mid lengths. Shhhhh...Don't tell my car that. I went 12.0 a few weeks ago with a 95,000 mile stock bottom end, and full weight...With the EGR and AIR tubes still in place!

Frank

 

Bet you'd gain MPH and ET with 1 3/4" headers.

 

Every time i have gone to the dyno , people have said that i would pit up min 10ft+ and the same with hp+ hhhmmmm?