Ok I have a 1987 Iroc with a T-5 and I have a few questions. I recently put a 1989 vette motor in it with the aluminum 113 casting heads. As you know these heads have the D port exhaust chambers. I purchased a set of flowtech headers and y pipe but they keep blowing the header gaskets. I have done a lot of research and it seems that the headers are not allowing full exhaust flow and are actually covering part of the exhaust chamber because of the D port design. My question is do they make a Y pipe that will fit with the T-5? I am looking at buying either hedman header part number 66479 or 68479(same header one painted and one HTC). These headers have a 3 inch collector but they suggest a 2.5 inch y pipe. I want to keep the 3 inch exhaust all the way back cause the pipes are already run. I think it would be stupid to step it down at the y pipe only. I found the 17534 y pipe from hedman but they say it will only fit 4th gens. Has anyone tried to use this setup or will it not work? Is there another y pipe out there that will work? I figure almost any y pipe would work if the headers dump in the same location as stock? Any help would be greatly appreciated. thank you.

 

Your last question is the problem. No aftermarket headers dump in the same place as the stock manifolds. The 1 5/8" headers are too small for the raised exhaust ports. You need 1 3/4" headers, either SLP's or Dyno Don's (member on this board). Every y-pipe for shorty headers for a thirdgen should work with a T5 or 700R4. I think they suggest a 2.5" y-pipe because that should be the pipe diameter from the four ports on each side, and then they join together to make a 3" pipe.

 

Changing the Y-Pipe only wont solve your problem, you need to use D-port headers...theirs a few different D-port headers available for 3rd gens. LT1 swap headers for example since they are D-port's.

First and foremost running a paper or even a composite header/collector gasket is just buying time before they blow out. Do yourself a favor and buy the MLS or copper headers & collector gaskets.

Also, a quick look at Summits website shows what you can use.

Hedman 68469 D-port LT Headers - $236

Put those on the car, than have an exhaust shop fab up a Y-pipe for you to connect to your existing Cat-back and you're set. That'll run you about $200 and thats that.

 

OK, I understand that I have to get the new headers from summit to fix the problem. My real question still wasnt answered though. Some shorties say that they would bolt up to the stock y pipe. Does anyone know if the d port hedman shorties will bolt up to the stock y pipe. If they do I could use any generic Y pipe and it would open up a lot more options. My end result might just be to have a shop fab one up but I wanted to see if i could just buy one and put it on myself. Does anyone even make a 3in inlet and 3 in outlet y pipe for our cars?

 

There are some that have a 3inch outlet to the cat, but none that I know of with a 3inch inlet from each collector.

 

There are no shorty headers that i know of that will bolt up to the factory Y-pipe without some slight modification.

Besides, you're better off ditching the stock Y-pipe in favor for a well made, good flowing aftermarket/custom one.

 

The stock y pipe is long gone. I just wanted to know if most shorty headers have the same y pipe so i can use lets say a hooker y pipe on hedman headers.

 

Nope, they are all different.

 

OK thank you for all of your help

 

My headers have the port raised .100 to work with D shaped ports, they also have full length 3/8th thick flanges 2 1/2" ball and socket collectors.