Headers and exhaust recommendations needed for LT4
Thread Starter
Pro
Joined: Mar 2002
Posts: 610
Likes: 1
From: Bluffton SC
Headers and exhaust recommendations needed for LT4
I'm considering putting headers on my LT4. Who makes a model that will fit an LT4 without having to make any modifications?
The next issue is if I add headers can I mate them to the rest of a stock exhaust system? or do I have to change that too? and can I still run the stock ECM?
The next issue is if I add headers can I mate them to the rest of a stock exhaust system? or do I have to change that too? and can I still run the stock ECM?
Pro
Joined: Sep 2001
Posts: 587
Likes: 0
From: Phx/but its a dry blast furnace kinda heat AZ
Re: Headers and exhaust recommendations needed for LT4 (914eener)
In order to keep the stock exhaust, you'd need to go with shorty headers. No ECM changes required.
Shorties vs. Long Tubes?..... let the dirt start flying :jester
Shorties vs. Long Tubes?..... let the dirt start flying :jester
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: Headers and exhaust recommendations needed for LT4 (914eener)
No long tubes will bolt to your stock cat-back.
Personally I used Hooker 2151 headers on my car. They are actually an L98 header, but they fit perfectly. The modifications to your stock cat back are minimal and are actually an improvement. You do away with the slip fit and go with a bolt up connection. Makes for getting the exhaust on and off a lot easier.
For your LT4 you will need O2 sensor simulators for any O2 sensors you may have after your cats. These don't affect how the engine runs, so the simulators just fool the computer into seeing a valid reading and not setting a SES code.
In my opinion shorty headers just aren't worth THAT much in the line of power. Long tubes are a very good proven gain while the reports of power gains with shorties are mixed. I've never seen dyno results to prove it one way or the other. If they give you any power gain at all it won't be the same you get out of long tubes.
Personally I used Hooker 2151 headers on my car. They are actually an L98 header, but they fit perfectly. The modifications to your stock cat back are minimal and are actually an improvement. You do away with the slip fit and go with a bolt up connection. Makes for getting the exhaust on and off a lot easier.
For your LT4 you will need O2 sensor simulators for any O2 sensors you may have after your cats. These don't affect how the engine runs, so the simulators just fool the computer into seeing a valid reading and not setting a SES code.
In my opinion shorty headers just aren't worth THAT much in the line of power. Long tubes are a very good proven gain while the reports of power gains with shorties are mixed. I've never seen dyno results to prove it one way or the other. If they give you any power gain at all it won't be the same you get out of long tubes.
Drifting
Joined: Jun 1999
Posts: 1,874
Likes: 1
From: Garden Grove CA
Re: Headers and exhaust recommendations needed for LT4 (khornet)
, Nathan has it right - the shorties offer no power benefit. I almost get tired of posting it, but the simple fact is that the factory LT1/4 cast iron manifolds actually outflow many of the common shorty headers.No matter what kind of header you install, take a lot of extra time to insure that it is well sealed and has no leaks. Defective or improperly sealed headers will allow air to enter your exhaust system, that in turn is read by your O2 sensors as a false lean condition, to compensate the fuel trim ratchets up - so in fact you end up running RICH.
Thomas
