How much HP can a muffler really add
 

I have an OEM muffler on my SC. I'm considering a 3.6 conversion but if that does not come about I'm looking for ways to make my doggy car a bit more snappy. Some muffler ad's claim 12-14 HP but I'm really doubting that...and they are $700 + ! Is there a reasonable muffler ... Magnaflow, Flowmaster, etc. out there that will at least allow me to feel the difference ?

I suppose if I did a top end and higher compression P&C's I'd get decent results too. Maybe a cam change. Can't run carbs in Kali, sadly.

engine = air pump

you will get a hp increase like that from going to SSI's. I dont think any muffler will give you that kind of increase with the stock heat exchangers

M&K Pre-Muffler, M&K Muffler and Steve Wong Chip.

That should get you something - and from what I understand the SW chip really provides better response at lower RPMS - which is more seat of the pants.

This is my plan - when I have some free cash.

thats the 3.2 recipe, SC's dont have electronic fuel injection (no chip)

ah, sorry.

Anyway call Ben at M&K if you want to discuss what he thinks his mufflers can do. He was very open to providing advice and zero pressure to buy something "now."

The stock muffler is very efficient on a stock motor. A muffler change won't get you much in terms of added power, but some aftermarket mufflers are much lighter than the original Porsche boat anchor. Often times the more aggressive sound + a few less pounds over the back end = Car "feels" faster.

If you put on SSIs and a sport muffler, you will really feel it. The engine will have more power, particularly at high RPMs, where the stock setup strangles the engine.

If you can't get the old gasses out, you will not get the intake to flow either.

Ssi's and an m&k two in one out really opened up 5-7k rpm on the 2.2L in my 68. Not much difference down low. Sounds cooler!

Some mufflers due produce 12-14 h.p. more than stock, just not across the entire rpm range. A muffler for a high revving motor (7,000 +) will be different than one for a lower rpm motor (like a 3.6). The SSI's will make a difference, and are good up to 6,000 rpm. I would start there then try some different mufflers. I ran a Flowmaster 80 on our 3.4 race motor with headers. It's power band was pretty good between 5-7,000 rpm then lost 15-20 h.p. above 7200 rpm compared to the Jerry Woods Phase 9's. I also installed baffles to quite it down on the street. The baffles produced a little better bottom end, but less at the top. Noticeable differences, but not night and day.

Mark,

Who cares how much power an aftermarket muffler adds !
When i bought my 89 Coupe it was bone stock and sounded like a sewing machine,sorry purists but that was my interpretation ... lol

Anyhow after adding a SW chip which bumped the redline to 6850 RPM's,an MK pre muffler and a Fabspeed one in two out muffler all i can say is that it was worth every penny.
The mental HP and the exquisite sound alone is worth the investment !!!

Cheers :)
Phil

Doc, IIRC, you are right to doubt those claims. Even w/ SSi's. A few people here have done SSi/muffler before and after dyno runs on SC's with less peak gains than that. (again, IIRC)

Though, the SSi's are lighter and prettier. ;) ...and your SC will thank you and will give some power gains.

aside: I'm surprised that anyone even posted after that first stellar, informative, reply. Wow!

Just to pick a nit, no muffler can actually add power. What we're really comparing is how much power is lost with different mufflers compared to open headers, right?

I had that thought too, at one time. But really, the muffler works in harmony (you hope) with the system.

As gumba says; "A muffler for a high revving motor (7,000 +) will be different than one for a lower rpm motor (like a 3.6)."

So, all one can do is optimize a solution. That is, it's not as simple as "engine = air pump." Exhaust gases are pulsing, and cooling as they travel out. Also, the A/F reaction is not always finalized, as it passes the exhaust valve. (remember air pumps?) Lot's going on.

Y'all be in CA......need to have a friendly smog guy before you can back date your heat exchangers and lose the cat. In my exprience, Billy Bob's smog can be convinced that early HEs are actually dual cats.

IF you pass the visual, most likey you'll at LEAST need to lean it out.

How much HP can a muffler really add
 

I have been reading a lot of posts about recurving the distributor. Even with the stock fuel injection. Maybe it's an option.

There you go bgyglfr, that's correct critical thinking.