What size exhaust should I run

[ProStreet68SB]

Originally Posted by baclay9

Wanted to bump this with my engine specs one last time for last minute opinions. I am ordering mufflers soon. I talked to the guy at the muffler shop and he acted like I was crazy for even considering 3".

go with your first choice, and run 2.5". 3" is absolute over kill, more than people will admit to on here. But I've been studying exhausts and what not for almost 10years now in search of power for different vehicles and 2.5 will be the most you need

[getbent]

ive got a 454 .030 over with dart heads and 2 in primary full legth hookers and im running 2.5 in pipe with magnaflow 2.5 in and 2.5 out , you should be fine with 2.5in

[KQQL IT]

I got 3'' on sbc 400 works great

[68 C-10 KID]

I have a 406 sbc that put up a low 600 hp @ the fly wheel. I have the hooker super comps with 3" Borla XR-1s with X pipe and never looked backed after I took the 2 1/2" flow master system off. Sounds much better.
I personally like the Borla's and Dynatech's
Most machine shops that dyno motors can tell you there is a lot of power loss in small exhaust set ups. Just my 2 cents.

[ProStreet68SB]

Originally Posted by 68 C-10 KID

I have a 406 sbc that put up a low 600 hp @ the fly wheel. I have the hooker super comps with 3" Borla XR-1s with X pipe and never looked backed after I took the 2 1/2" flow master system off. Sounds much better.
I personally like the Borla's and Dynatech's
Most machine shops that dyno motors can tell you there is a lot of power loss in small exhaust set ups. Just my 2 cents.

lol most good ones wont say that. also what size primaries are you running on your motor? I bet those are too big also.

[68 C-10 KID]

Originally Posted by ProStreet68SB

lol mostgood ones wont say that. also what size primaries are you running on your motor? I bet those are too big also.

I'm running 1 3/4"
I left out the part about the collector type if its a short merge or long.

[lakeroadster]

Here is a good link for sizing exhaust systems and a chart, Looks like 3" is the minimum size you should be running:

http://www.magnaflow.com/wideopen/performdata.asp

Hope this helps!

[Super73]

Again, back to back dyno's with mine going through 2.5" mufflers to an open 3", I picked up power everywhere from 3,000 (where I started the pull) to 7,000 (where I lifted on the pull). I gained a min of 19rwhp and as much as 25rwhp through that 4,000 rpm range. There was no loss of power under the curve, period.

Every other one that I have checked as well on the dyno gained:

3" system open vs 3" open lost zero TQ from 2,400rpm all the way up to 7k.

3" system necking down to dual 2.5" through mufflers vs open, again gain from 2,500 all the way to 6,700-7k depending on motor with no loss of low/mid range TQ.


Perhaps it is a lot to do with the cam profile/headers and scavaging, but I have only seen a gain with bigger or even open for that mater. Never a loss.

Is there too big or over kill, sure. But I think most of that is in header sizing which in my opinion is much more important. Valley's in power bellow the curve can be addressed with different valve timing.

[Gobbles]

Ive got dual 2.5" exhaust into flowmasters, not sure which model, PO put them in. They sound great, little bit too much bass drone but it isn't my daily either.

Edit: running off my 454