irocz2173

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.

Kevin91Z

iTrader: (1)

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.

Z28 MeTaL HeAd

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.

irocz2173

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?

86blackiroc

iTrader: (12)

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

Z28 MeTaL HeAd

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.

irocz2173

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.

86blackiroc

iTrader: (12)

Nope, they are all different.

irocz2173

OK thank you for all of your help

Dyno Don

iTrader: (7)

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.