Im trying depererately to purchase a set of headers but no one seems to know anything about the fitments for the swap. Many have said purchase TPI headers for my LT1. Ok, fine. But I must stay emission legal and must have the A.I.R. The LT1 AIR fitting going into the manifold appears larger than the TPI's. Is there a reduce that you can use to connect to the TPI header from the LT1 AIR fitting? Is it at all possible to use LT1 headers w/o posing a large problem?

 

This could get a bit tricky...

The headers your looking for are not made to fit your car, you still need to be looking for a set of third gen headers or else youll end up with all sorts of fitment issues. Then modify them accordingly.

 

Let me preface this by saying that I haven't performed the LT1 swap in the thirdgen, but I've had several thirdgens and have a LT1 4thgen currently (which I just did a header swap on so I've messed with both the AIR and EGR setups for the LT1).

You shouldn't have much problem w/ the AIR setup, but see below about the EGR. You don't need anything to thread down into the 3rdgen headers for the AIR, they (at least the Edelbrock TES units) have the airtubes coming up and out to a threaded junction for the black diverter/check valves (what I've heard then called, not 100% if that is the correct name) to thread onto. Then a rubber hose connects to the back side of the diverter valves and runs to the AIR system. The LT1 setup only differs in that it's headers reuse the factory metal tube that threaded into the stock manifolds, that the diverter vavles then threaded onto from the factory, you just won't use those tubes... The black diverter valves will thread right onto the thirdgen headers and then you'll just rig up the rubber tubing to work. Should be dirt simple to get that hooked up unless I'm overlooking something, probably need to splice another piece of rubber tubing in to get it hooked up but that's nothing.

See this pic to see what I'm talking about, notice the airtubes coming out of each header and going up to a threaded junction for the valve. http://static.summitracing.com/globa.../edl-68723.jpg

I've only used the Edelbrock headers in thirdgens myself, but I believe all the thirdgen emissions legal headers have similar AIR hookups.

Further more, the AIR system is electric powered in the LT1s, and only runs for a few minutes at startup to warm the cat quicker, unlike the older thirdgen smog pump setups where it ran all the time. As such, it won't actually be doing anything while you're doing an emissions test and will not effect the numbers in the least as you'll already be warmed up. You can merely unplug the AIR pumps electrical connection to disable it, then you could just mock up the tubing if the emissions test guys where you're at do a visual check. Note that if you have a 96+ OBD2 LT1 this will throw a code and light the SES light, have to have it programmed out of the PCM. On the 94-95 LT1s at least if the fuse or relay for the system is still in place it causes no problems. I disabled mine when I did the header swap on my 94 a few weeks ago...



The real problem is going to be the EGR tube. I don't know what year your LT1 setup is or if the EGR setup varies through the years (don't think it varied significantly anyway), but on my 94 the EGR system has a metal tube that runs down and bolts into the manifold/header. On the thirdgen headers you'll have no provision for this at all. Gonna have to rig up something and I'm not sure what would the be best/easiest way to tackle that. The tube runs across the back of the head and plugs on the passenger side header above where the y-pipe hooks up the headers, hard spot to get at with it in the car anyway... One of those kits for plumbing the EGR into the header for running EGR w/ Vortec heads that Scoggin Dickey sells might be helpful since it's a similar idea, but I have no idea really... Pic of the factory EGR tube setup: http://shbox.com/1/EGR_pipe.jpg

You're going to have to get some kind of bung welded onto the headers to hook up the EGR. See this thread a little ways down for a pic of Vette heads with an external EGR tube plumbed into the headers, you'll need to rig up something similar: https://www.thirdgen.org/techbb2/sho...ht=scoggin+EGR

 

I'm not sure about all the A.I.R. stuff becasue I got rid of the EGR in my swap. I found out by experience that headers made for an LT1 WILL NOT WORK ON A THIRD GEN. I bought a set of Hooker Super Comp shorties and had the EGR stuff machined off of them before I started my swap. I wanted to have all the parts I needed so I didn't have to wait for any. The headers hit the frame before they even came close to lining up. I then bought a set of Hedman headers that where made for a third gen but they are also made to clear angle plug heads and made for aluminum heads with D shaped exhaust ports. I can get to all of the plugs on my LT1 on the drivers side with no problem. The back two on the passenger side are extremely hard to get too. I have found out that the easiest way to change them is from under the car and then it isn't that hard. The part number for the non EGR is HED66749 or just 66749. I bought them from a buddy who had a performance shop and he found the ones I needed. The part number for the EGR ones shouldn't be much different.

 

EDIT - nevermind, thought this was the usual "will 3rdgen headers fit an LT1" thread