What size is the Hedman Y-pipe #17470? 3"?

 

3" collectors down to 2 3/4 pipe then it has a adaptor to goto 2 3/4 to 3" for the I pipe

 

Header Gauge Flange PRI OD PRI ID COL OD Col ID Pipe OD Pipe ID CAT OD CAT ID

Hedman 68470* 18 0.25 1.63 1.53 3.00 2.80 2.25 2.15 2.50 2.40

As per the header options sticky, where you see 68470 it's with the 17470 Y pipe.

So its 2.25" pipe from the headers to the Y collector and then 2.5" after. A common? mod is to cut the pipe after the Y and replace with 3" mandrel bent pipes.

Si.

 

So at the headers its 2.5", and the I-pipe part is 3"?

 

No. You've simplified it way too much.

The primaries are 1 5/8" (this is the pipe from the head)
After the header's collector it is 2.25" (after the 4 to 1)
After the Y pipe collector it is 2.5" (this is the bit that connects to the rest of the system to the rear)

The only bit of that system which is poor is the 2.5" section. I've heard of folk replacing the section after the Y collector with 3" mandrel bent pipe section to improve it considerably.

Si.

 

I have the 68470 headers. They are 1-5/8" primaries and 3" collectors. I know because I measured them. So I know about the headers, I already have those.

Its the y-pipe I need to know about. So you are saying that the main pipe (the one that a cat-back would hook up to) is 2.5"?

What size are the other two pipes? The ones that connect to the headers? Those are 2.25"?

 

Yes each pipe that bolts to each header collector is 2 1/4 inches in diameter. And yes the main piece is 2 1/2 inches in diameter. But as already stated you simply cut off the 2 1/2 inch piece and have a 3" MANDREL bent piece installed instead. I did this already on my GTA. If I ever get it up to the track this month I can show you how it turned out.