Exhaust system for '66 GMC 305E V6

[athan66]

I'm seriously thinking about upgrading the exhaust on my truck. Right now it has a 2 inch single system that does not sound very good and seems to be quite restrictive.

Since my truck is pretty much stock, should I opt for a larger diameter single system (2.5" or 3") or go with a true dual system with 2.5" pipes?

If I go single system, I would have the pipe exit behind driver's side rear wheel. If duals it would be either straight out the back or side exits behind the rear wheels.

For mufflers, I like the sound of Dynomax on V8 engines, but I have not heard them on the V6. Torn between Ultra-flos and the quieter Super Turbos. I realize many like Flowmasters, but I'm not sure the sound does it for me.

Appreciate any and all input and suggestions here

[Corts60]

Personally, I wouldn't go bigger than 2.5" and that may even be too big for these v6's. These engines create peak torque around 1200 rpm, have 7.5:1 compression, and have a super mild cam so I wouldn't be too worried about exhaust restrictions. A nice set of 2.25" duals with an H pipe would be probably be just about right for this old girl. Just my opinion.
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[Billett]

I'd suggest the same. 2.5 is big for a stock 350 v8 so its a bit much for a v6. 2.25 would get you by and an H-pipe is always a good idea. Mufflers on the other hand are all about your own opinion on sound. Lots of people swear by their preferred brand or style, but it really comes down to what sound you like to hear every time you start her up.

[athan66]

Thanks for the quick replies guys. Regarding the tubing size, most of the generic research I've done suggests what you recommend -- 2 1/4" max for this application.


On Jolly's site however, he seems to suggest a much larger size in his performance upgrades section (hopefully no issues in copying this here).

"Better Exaust System
Dual 2-1/2 to 3 inch exhaust pipes is a nice improvement, and the 50 series Flowmasters Mufflers sound great on these engines. "

[Billett]

I was recently looking into the same thing and what I found, (take it at face value since everything on the net isn't true), is that you could probably use 3" pipe, but in general it is used on higher performance engines. I have a stock 350 so 2.5" is perfect. If it was a built stroker then 3" would be much more suitable. What I'm trying to say is that with your motor 2.25" is fine, but if you upgrade your internals and pour more power through it then a 3" exhaust would certainly help it breathe better and gain some more hp. Stock motor and the 3" pipe decreases exhaust velocity and will make you lose a bit on the low end.

Again, just stuff I've read on here while doing my research.

[1Bad62Pro/Street]

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