New down pipe question

[86Tona]

Was there any 2.5" application from the factory on a G body or other that would work on an '86 Daytona?

[tkelly27]

I don't think it's an issue with the downpipe, I think it's the swingvalve that is the problem. If you had a 2.5" swingvalve I think it'd go... don't quote me on that though

[daytonajesse]

86 had 2.25" swingvalve and downpipe, you could have a shopmake a downpipe with a transition from 2.25" - 2.5" to help you out a bit but getting a new swingvalve will help more.

88 T2 cars had a 2.25" SV with the large flange that bolts to a 2.5" exhaust.
89 T2 cars had a 2.5" swingvalve and the large 2.5" flange for 2.5" exhaust.
all other stock turbo cars with a garret turbo had a 2.25" swingvalve and the small 2.25" flange for 2.25 exhaust.

[86Tona]

89 T2 was the only year with the 2.5" swing valve and large flange? Did they keep these (the size) in the later years like '90 and above? It sounds weird that they would use the larger size only in '89. What did the T3 have I wonder?

[daytonajesse]

Not sure on the T3 cars Sv size.
They only made T2 cars for 87-88-89 thats why only one year for the true 2.5" SV.

The only other 2.5 SV is on a mitsu turbo 89 and up I think, and it is not compatible with a garrett turbo

[glhs727]

The 89-up cars had a 2.5 inch downpipe. They are fairly universal. To use on a 2.25 swingvalve, all you have to do is elongate the bolt holes on the DP flange until they match the spacing on your 2.25 sv. They will bolt right up. Use a new 2.50 donut.
later,
Cindy

[86Tona]

Thanks to all. When I go with the 2.5" down pipe I'll change the entire system. This will include the swingvalve to include a change to the 2.5" as well.

[Michael_Valentine]

Quote:

Originally Posted by glhs727 The 89-up cars had a 2.5 inch downpipe. They are fairly universal. To use on a 2.25 swingvalve, all you have to do is elongate the bolt holes on the DP flange until they match the spacing on your 2.25 sv. They will bolt right up. Use a new 2.50 donut. later, Cindy

I'm interested in your 2.5" Kit for my 86 Daytona Turbo Z and was wondering if you had any pics showing what you mean with elongating the bolt holes on the Down Pipe. Thanks!

[tryingbe]

Your FWDperformance Team
281-288-4411 or 281-642-3878

[87dtna]

The factory downpipe is 2.25 for the first few inches and then flares to 2.5'' down to the cat. After the cat it comes back out 2.25''. Cut the exhaust off right before the cat and bam instant 2.5'' pipe there to start with. It's not worth messing with downpipe spring/bolts and donuts plus cutting the flange. Just let the stock downpipe on take a sawzall and cut off right before the cat (cutting the cat off), and you have a perfectly good 2.5'' pipe to start with. There will be no gain for your trouble of putting a full 2.5'' downpipe on the 2.25'' swingvalve, so let the stock DP on there.

[crazymadbastard]

Quote:

Originally Posted by Michael_Valenti I'm interested in your 2.5" Kit for my 86 Daytona Turbo Z and was wondering if you had any pics showing what you mean with elongating the bolt holes on the Down Pipe. Thanks!

Here you do it to the flange you grind away the red with a dremel or a file, here is an ultra precise 3d autocad, it took me 4 hours. Hope it helps!

[Michael_Valentine]

Cool, I figured this is what she meant, but wanted to be sure before I start grinding away at a $100 + piece! Are the Swing Valves easy to replace? I was told not to mess with it since I might break the bolts and cause myself a nightmare. The Turbo was rebuild about 3 Years (6000 miles) ago by the previous owner so it might have been removed during that time.

[crazymadbastard]

Quote:

Originally Posted by Michael_Valenti The Turbo was rebuild about 3 Years (6000 miles) ago by the previous owner so it might have been removed during that time.

You might be ok as long as the bolts weren't overtightened and antiseize was used. There is one bolt that you have to stick your ratchet with a short socket into the exhaust hole to get at it.

[Michael_Valentine]

Thanks, what is the best way to remove the swing valve, from underneath or from the top? Nothing more than basic hand tools required..correct?

[87dtna]

So you are replacing the swingvalve too or what? If you aren't putting on a 2.5'' swingvalve than replacing the factory downpipe is a WASTE OF TIME and effort AND money. The factory downpipe is 2.5'' at the cat, and you will see NO GAIN whatsoever by all this work to put a 2.5'' downpipe on a stock 2.25'' swingvalve.