Performance Exhaust

[Sidewinder]

I just had a question about exhausts. I've heard that if you don't do other mods (like ported intakes) you can actually loose low end power if I was to get headers and performance exhaust. Is this true?

So if I got ported intakes would that help?

[blackbombshell95]

If you got a large 2.5" exhaust you might loose a little low end but gain a little on the top end. Headers would make a difference in power throughout the whole powerband with no other mods.

[Ortie666]

I wouldent worry too much about the low end that is lost, because it is so small compared to the gain of top end, and long range power that is accomplished by headers, and high flowing exhast.

[IsaacHayes]

Ported intakes would actually help more on the higher RPMs not low.

With 2.5" you'd probably loose the scavenging effects from the exhaust at low rpms since log manifolds don't help with that and larger pipe would require more flow to keep velocity up. But if you have headers then you have solved that problem. I felt an increase in low end when I removed the resonator and went to a straight through muffler. I still have 2" exhaust and that super small downpipe though.

I do plan to go 2.5" sometime in the near future but I won't have headers cause no one makes any that clear the firewall angle for my car.

I hope it doesn't harm the low end too much, for highway cruising. Because one good benefit of my mods so far is highway cruise doesn't down shift every 5 secs for every slight hill like it used to. 70mph = like 1800 rpm on my car, so I need some low end power to keep it from moving out of 4th.

[3100 MPFI]

keep in mind that it is about a BALANCE. If you do something to free up the exhaust, then for best results, you will want to do something to the intake.

Does no good to free up the intake if the EXHAUST is restricted. Does no good to free up the exhaust if the INTAKE is restricted.

If you do something on one end, you will get that much more by doing the other end.

If nothing else, if you don't get headers, then have a custom made downpipe. The stock downpipe is a lot smaller than you think. It is a SHIELDED pipe, so the inner pipe is small. The inner pipe on my 1996 3100 SFI was less than 2 inches.

PICS!!!!!



That is the stock 3100 downpipe.

[95Grand-Am]

My grand-am 's downpipe was just like that one. I cut it in to three peice to get the center pipe out then i welded it back together.

[Superdave]

this is a typical gen3 downpipe flange..



around 2.5" at the top then a funnel down to around 1 7/8" inside of it.

cutting that out should gain a few easy HP.

[Sidewinder]

Well, I was thinking of getting headers and 2.5 inch mandrel bent exhaust with performance cat and muffler done sometime soon. Eventually I will be getting ported upper and lower intakes manis, 65mm throttle body and 3400 heads. I can't afford all of it at once, but if I do the exhaust I want to do it all at once with the headers.

[IsaacHayes]

Yeah I plan to have all new downpipe made. I *know* my intake mods are really being choked out.

[BillS]

You don't want to go too large on the primaries or you can lose out, but further down the system you can reduce backpressure by going larger. I run a 2 into1 system with a low restriction straight through muffler and tip resonator that is 2.5" all the way from the point the two sides of the system join and it works well.

[Sidewinder]

Well, here are my options right now:

1) I can get a full performance exhaust from the headers back to a high flow cat and performance muffler. I priced this out, the headers are about $600, and the full exhaust I got quoted for around $1000, so $1600 altogether. This may have changed now with the high Canadian Dollar, but I highly doubt it.

2) I could get Milzy's new ported exhaust manifolds instead of the headers, which will reduce the price to $1250 instead of the above.

3) I can get engine parts instead, specifically either a 3400 top swap, or a 3400 top swap with a 3500 upper instead. I've been quoted at $375 for the 3400, haven't got one with the 3500 upper yet. As for the exhaust, I can do a few things. I can either stick with my current exhaust manifolds, get a 3400 rear mani (about $40), or get ported manifolds ($250ish). After that, I could take the fake dual exhaust from my 95 monte z34 parts car and get the downpipe cut of and have a new one welded in (i'm going to guess at $60 - 100.)

So that would make for:
- $475 for the top swap and having the fake dual welded on.
- $515 for top swap, 3400 rear mani, fake dual.
- $725 for top swap, ported manifolds, fake dual.

I've also found out that I may be able to get porting done for free, so that may change costs a bit.

So what do you guys think? Which would yield better results?

(Side note: Its nice to finally narrow down what I want to do to the point where I am ready to buy parts!)

[RedogOnyx]

You can start small and just do the exhaust.

I personally gained time in the 1/4 mile from exhaust. Don't remember 60' times from before and after but the end was better than before.

Plus I had one of those crappy rice mufflers when I didn't know any better, switched to a Flowmaster and dropped .2 to .3 tenths in the 1/4 mile, no lie. I was surprised too.

Headers is always a good idea. If I could have done "Headers Back" when I got the exhaust I would have. I would do headers back right now, and do the rest when you have the money

[El_Diablo]

$1000 for an exhaust? even in canadian your getting ripped.... you should be able to get a very nice system for under $650-700 at the very most!!

[Azrael]

Look for exhaust manifolds from an 05 Impala with the 3400. They were originally designed for 3500's and have significantly larger ports and internal diameter but still maintain the old log-style design. Should be more effective than Milzy's ported older ones and cheaper to boot. I'm currently looking for a set of these for myself.

[Sidewinder]

$1000 for an exhaust? even in canadian your getting ripped.... you should be able to get a very nice system for under $650-700 at the very most!!

Yeah, it is definitely a bit steep, but they do fantastic work. They did my dad's Suburban as a TRUE dual setup from his headers, it sounds awesome and gave it so much more power. The shop was also recommended by my mechanic, the other shop I went to was a POS.

Look for exhaust manifolds from an 05 Impala with the 3400. They were originally designed for 3500's and have significantly larger ports and internal diameter but still maintain the old log-style design. Should be more effective than Milzy's ported older ones and cheaper to boot. I'm currently looking for a set of these for myself.

Really? I didn't know that they had a different style 3400 manifold. I'm gunna have to look into that.

So specifically the 05 Impala? Anyone know if these would work on a 3100?

As a side note: I may try making a front powerlog since I know someone who can weld.