keep shorty headers or replace with longtubes?
Definitely go with LT's. According to alot of people on this board, save your money and buy some kooks or qtp's. They seem to be well worth it.
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I have shorties their decent but LT's and Midlenths definitly do help out ALOT more all in how much you want outa your car Essentially shorties flow better than stock manifolds, but that's not what proper exhaust tuning is about. It's about scavenging. On an n/a/ engine you can introduce a 5 process into the combustion cycle, this is where via scavenging you can increase air velocity into the cylinder. Proper exhaust tuning can contribute up to 80% of the air velocity. So it plays a major factor.
Primary pipe length will determine the rpm range that scavenging takes place, as you need to have each pulse arrive in the collector at the right time in order to scavenge from the other cylinder on the down stroke. Get this timing wrong and scavenging will not take place.
Shortie manifolds need very high rpm in order to scavenge effectivly, possible somewhere around 9000-10,000rpm hence people don't see much gain with them. Mids work better in lower rpms but they still prefer high rpms for best benfit. Long tubes will allow scavenging at the lowest rpms, which suits the LS1 best and will offer the best torque and hp over the entire rpm range.
Now the only time this is different is on a supercharged car, as the intake air is actually being forced into each cylinder under a constant, so scavenging can not take place to the same extent. Flow is more important on this kind of setup as it will releive back pressure and extract hot gases quicker, this means you can run less boost for the same gain (or the same boost for more gain) it will also reduce the risk of detonation.
So therefore the choice you have is:
1. If you plan on n/a cammed setup get the long tubes as they will be a benefit. And will still work on a supercharger setup also.
2. If your plan is to get a Pro-Charger or similar pretty soon then the shorties will offer very similar gains on a blown application. So you can save yourself some money and hassle.
Disclaimer
This is my interpretation of information I have read, researched & collected on exhaust setups and designs. Therefore please use your own ability to verify or disprove any claims if you feel they are inaccurate.
300bhp/ton, are you like an LS1 supertech, or do you just do your homework?
anyways have fun with your LT's!




