I'm after some peoples thoughts on what size exhaust to put behind the 304 in my VL. It is an EFI 5L out of a VN that has a mild cam, 775 injectors and a Chip Torque stage 3 tune. It has HSV extractors and runs a T5 gearbox. I was considering either a 2.5" or 3" single system. Not sure which would be better. The car will be mainly for cruising on the streets at this stage. I still have a high flow cat from my old 2.5" system that I could use as well as some of the pipes. Not sure if 2.5" is too small or 3" too big?! Any input would be great.

Single 3" probably the way to go. That's what I had on my stock EFI 304 to start with, then when I supercharged it I didn't have to upgrade the exhaust to suit

Maybe a twin cat system into a 3in dump just before the muffler then a 2.5in tail pipe so it's not too loud but still flows. don't forget a resonator.

EVLHSV how did you find the 3" on the stock 304?

3inch all the way, best for a mild 5L, once you put some cam and comp into it id go twin 2.5inch. every 5L ive ever owned has only had 3inch to the diff, cant beat that rumble!

Quote: Originally Posted by Farrout [View Post] EVLHSV how did you find the 3" on the stock 304? It was fine, but I didn't drive it before it was installed

i ran a twin 2.5 inch stainless with 2 ultra flow mufflers exiting out twin 4 inch tips from diff to rear that was in a vl 355 get rid of the hsv ext i had pacemakers sounded loud and distinctive note, good luck with it

Well I think I'll go with a single 3" system. Regarding the resonator would this make the exhaust quieter or just stop the "drone" when cruising? Would a single muffler be sufficient to get it registered?

I had paceys, single 3" system. Sounded nice but was fairly loud.

Single 3" with 2 chamber Flowmaster and 12" resonator at rear (no cat - we don't need them in NZ) Here's how it sounded Some original photos have not been recovered yet.

EVLHSV thanks for posting the vids, sounds pretty nice.

I'd go for a twin 2.5 inch system personally , mainly for clearance purposes ,go for either a single 3 inch resonator or twin 2.5 inch if fitting one. I've found out you've gotta be careful who you get to do the work, when I bought my SS , the bloke who used to own it was quoted $4000 to weld up the header pipes to the cat converter pipes (has a custom sports system fitted) because it was never done when the car was new, they wanted to take the engine out. I got it done locally for $50 and it only took about 1/2 - 3/4 of an hour to weld the pipes up , I couldn't do it myself as it needed to be done on a hoist , this was done without removing the engine.