My Custom 2.5 Inch Down Pipe 3100

[IsaacHayes]

So you just cut the downpipe off the flange flush and welded new on? How does it seal stock? Do you unbolt it and bolt it on and you're done? or does it use a gasket too?

I need to do this as it appears I won't be getting headers after all. I REALLY wanted headers as that would make a lot of power, make me want to tune it, and later drop in a built motor. Now not so much.

But I still need to do something to get a little more power. My motor needs to breathe! Too bad I can't make the stock 3100 really scream. But better exhaust will help, as your "4-6k" does move faster than mine, and my top end is crazy compared to stock.

[Monzsta]

94 GP

I didn't use a ball/socket on the end, that is a 2.5" to 2" Reducer to fit my stock pipe......I then welded them together....

I will upgrade to 2.5 back soon though....

What I mean is your manifold flange has a pivot built into it. You have spring bolts, right? Mine simply bolts up flat, and my factory down pipe had a flex piece made into it.

Yours > Mine.

[19Cutlass94]

So you just cut the downpipe off the flange flush and welded new on? How does it seal stock? Do you unbolt it and bolt it on and you're done? or does it use a gasket too?

I need to do this as it appears I won't be getting headers after all. I REALLY wanted headers as that would make a lot of power, make me want to tune it, and later drop in a built motor. Now not so much.

But I still need to do something to get a little more power. My motor needs to breathe! Too bad I can't make the stock 3100 really scream. But better exhaust will help, as your "4-6k" does move faster than mine, and my top end is crazy compared to stock.

Theres a dounut gasket that goes on the rear manifold. Theres two bolts with springs on them that hold them on. ( talking about stock here )

I know when my 3100 was stock, the exhaust really wakened it up ALOT.

[IsaacHayes]

I need to research exhaust gaskets, I always hear donut gasket but never have seen one LOL.

(woke you mean)
Mines not stock, so I hope just plain exhaust will wake it up. I wonder if the GAGT 3400's downpipe is the same way, and part of the 18hp to the wheels they get from headers is getting rid of that small downpipe... Anyone know if theirs is that small too?

[Barry]

Haha awesome welds. I used to suck at welding pipes, but after repairing 3 exhausts, i picled up on it pretty quick. Ill be making my whole system from scratch this summer. Well see how that turns out.

[AWeb80]

I'm guessing I got at least 8whp out of the DP.....might have more w/ full exhaust....I'll try and get a dyno graph when done.....I already got a stock chart

[IsaacHayes]

Bitchen! That'd be great if you could get a dyno of the full 2.5" setup. Then we can see how BAD the stock stuff is. 8whp is a lot, that's at lest 10 at the crank.

[19Cutlass94]

when I had a DP made for mine, it was such a difference. I wouldnt doubt it free'd up that much power.

[IsaacHayes]

Aweb: is the rest of your exhaust stock other than no cat?

Jay, when you did yours did you do the full exhaust at the same time? I don't remember.

When I did the LA1/LX9 intakes the difference took a while to be felt (LTFT/BLM had to adjust). At first it felt slower (cause the battery was disconnected, stock this would happen too). Then a week or so later I was like damn when I went WOT. It's not crazy throw you back in the seat (but passengers say it does) but does pull better on the highway especially.

[19Cutlass94]

When I had my exhaust done, I had from the cat back done in 2.5" first. I felt a HUGE difference from that with the srock DP. Then I had the 2.5" DP made, and you could still feel a difference from that!

[AWeb80]

Yes....stock back from the DP.

so, custom DP, no cat and the rest is stock 2".

[IsaacHayes]

Nice. Sounds like both the 2.5" back and the downpipe give good increase on their own. I thought W body's had bigger exhaust anyways than L bodies. I know the new 3400 impala's it's much bigger pipe than my car. Probably 2.25". I don't know about their downpipes though if it's restricted like ours or not. Anyone know?

[1995 Gold Ciera]

I'm guessing I got at least 8whp out of the DP.....might have more w/ full exhaust....I'll try and get a dyno graph when done.....I already got a stock chart

Seriously?!?!?! That much? WOW!!! I was thinking I was only gonna get about 5-7 hp with a full 2.5" exhaust including the DP but this is even better!

[fordboy97f150]

so does anybody know about the 3400 dp?

[3400-95-Modified]

What about it?