This may be old news to hardcores, but thought I would post this new and save others some grief.

Spoolin4days wrote:Does any one know if the factory LS1 exahust manifolds will work in a S13? Hopefully I'm not asking too much, but I just want to know what Im getting into before I start ordering parts.

Just got through putting a '99 Firebird LS1 / T56 into an '89 HB. The stock LS1 manifolds (Tube type) would have worked OK on passenger side but after cutting and welding on the driver's side, finally gave up and installed LS2 crate motor (Corvette?) takeoffs. Passenger side fit perfect, on driver side we installed a GM exhaust flange part#?????? between the manifold and head. This flange is what one would use when making headers. The flange spaced out the manifold perfectly to allow the downpipe to go straight down right next to the frame rail. A cheap and robust alternative to headers when performance is not as big an issue.

If anyone is interested I will try to get some pix. Added pix,

Modified by gofastnow at 7:52 AM 8/11/2009
Modified by gofastnow at 2:16 PM 8/11/2009

just upload pics !! =)

this is a great option for guys who don't want to pay $600+ for headers! It seems so simple, i'm surprised no one thought of it before.

Thanks for this input!

Update- A guy on another forum said he tried this some time back on his install where he had put in a motor mount kit from a 240sx supplier and he could not fit the manifold as it hit the motor mount. My mounts were custom made and must be different from his. I did have to remove the output studs from the manifolds as they were quite long and hit the motor rear (firewall side) mount upright that is on the chassis side of the mounts. I used socket-head cap screws in place of the two studs and these worked well, did have just a little difficulty getting a long neck ball end hex tool by various obstructions while tightening.Hope this helps.

Dang...thats an awsome idea. I doubt it will hurt performance at all so long as they are gasket matched. You should be able to get those flanges all over eBay.

Well done sir

WD