Ive got an LO3 with a flowmaster 40 series crossflow muffler. It's 2.5" in and out. It appears the rest of the exhaust is also 2.5" Theres no cat and stock manifolds are in place. Im thinking about getting Hooker 2055's with the y pipe sometime soon. Will this setup flow enough for my motor, or do I need to replace everything and go 3". I dont have the cash to replace it all at once, but would like to put on headers by mid summer. Im NOT absolutly positive it has a cam in it, if it does, it's a very mild one. I was told it might, but Im not going to pull it out just to check. Next year I am also thinking about the possibilty of intake, larger cam, and maybe heads too.

 

You don't need a 3" exhaust, hell I wouldn't even do that on a 350.

 

Yes he does.

A 3" exhaust really is too small for most V8 motors. A 3" is a good mix between flow area and ease of fitment. That is why the aftermarket tailors their systems that way. How can you say that you wouldn't run a 3" system on a 350 when there are 397484937584 dyno tests out there, on stock V8's produced over the last 30 years, that say otherwise? If you are refering to a true 3" dual system than your statement would hold some merit.

A 3" exhaust will be benificial to you down the raod. The 2.5" system that you have now will suffice but there would be gains with a 3". Since your LO3 is pretty low on power the power difference between the two isn't that noticable yet. When you add a cam you will want to go at least 3".

 

I kind of figured that, but wanted to make sure. I am not going to be able to replace the whole thing right away, but if I can run the 2055's with what Ive got for now, then Ill swap the rest later. Ive read a bunch of posts over the few years Ive been on this forum and most pointed to 3", but IIRC most were also either more built up or 350's. I guess 3" is a good future investment for the possibility of either head work, aftermarket heads, or a 350 swap.

I guess now it comes down to buying either a 3" catback for now or the 2055's. I can't get both this year.

 

Buy the 2055's and just place a reducer on the end of the y-pipe to mate to your 2.5" system. You will see your largest gains on an LO3 car with headers. When you get into chip work you will see up to a 10% increase in the VE with a full 3" system. That is enough verification to warrant the validity of a 3" system on even the meekest of V8's.

 

Shot you a PM back devestator.

And MKnight.. any V8 ever made would be much happier with a 3" exhaust.