Guttermouth

Hey all,

Been asked a few times but I can never really comfort myselve with the anwsers that are given.

My car (cutlass supreme 455 th400) is going for a custom exhaust from headers to tailpipes. But I've been doing some research on the diameter. I usually end up reading: Just go with the duall 3" and have room to grow. Or when reaching 550 hp go for duall 3''.

But the thing is, I've never had my car on a dyno and I do wanna grow in the future but I can't tell how much hp my car is gonna have.

My current setup is: K&N airfilter, Edelbrock 750 carb, Edelbrock torker intake, hooker competition headers (3'' collector)

Where I would like to be is: Above + Ported edelbrock heads, rocker rollers, different cam (will research about that later) Full MSD ignition and all the bits and ends that come with these upgrades.

And maybe in the far far future when I won the lottery I'd like something like: above + lightweight rotating assembly, maybe 461/468 stroker (depending on oversize) and strenght girdle. and again bits and ends.

So what would be the best size considering the upgrades in the future (not the last line of upgrades, that probably won't happen, but a guy can dream right)

The car is by no means a daily driver, but still a street vehicle, and maybe an occasional trip to the strip.

thnx in advance,
Clint

Guttermouth

So is there anyone with a similar setup with a 2,5 or 3 inch exhaust, or someone that knows from experience that 2.5 would or would not be to small with the power my engine is making with the parts mentioned in my above post.

Sorry for posting again. But my shop needs to order the pipes and needs to know what to order.
Greetings clint

Mikes65

2.5 will be fine for any street use unless you plan on revving 8000 + and looking for maximum output for racing
The 2.5 is better for low end street torque
If you build an all out race motor for the street you will be dissappointed

oldcutlass

X2 with above.

TripDeuces

http://www.magnaflow.com/07techtips/faq/question10.asp

One manufacturers advice.

http://www.boyleworks.com/ta400/psp/exhaust.html

Another take on it.

rjohnson442

I run a 455 with a 750 Holley Aftermarket heads think hooker but have no idea who anymore 3" collector 2.5 in pipe back. I put some electric cutouts on they end right at the mirrors. I have notice a loss of torque at launch but this has also helped me hook better and I can close them for more back pressure on the second half the track. My neighbors love me now in the morning

Gunmars

Agreed. I just built a supreme with a 488 stroker and have 2.5" on it. Sounds better than I ever expected and makes pretty substantial torque. Unless you want to make the jump into a more than just occasional trips to the strip I don't think there is any significant advantage to getting 3 over 2.5

Finn5033

Sorry to butt in on this thread but I bought a 2.5" x-pipe system for my cutlass with a 70 350 built up to about 400 horse. Is that exhaust too big for a small block or will I be ok?

gearheads78

3" to the X with 2.5" back. Works very good on 450-500HP street cars.

Mikes65

Richard
That 54 is gonna be sweet- love that front end

oldcutlass

Your fine.

oldcutlass

I'm a big fan of cutouts, they are especially impressive at a traffic light.

Guttermouth

Thnx for all the replies guys,

2,5'' it is. Lil cheeper too

much appreciated,
Clint

gearheads78

Thanks Mike