My 65 442 is 4 speed and all original, has standard exhaust manifolds. pipes out back appear to be 2". not sure what collectors are but have been told 2 1/2 or 3" out is the way to go . any thoughts on that appeciated !

 

Not sure how modified your engine may be - since you have the factory manifolds on it I'll assume not too wild. I would avoid 3" without question. I suspect you might actually see your street performance reduced with this size. Way too big for anything other than pretty modified engines moving a LOT of air. 2.5" is fairly common and will work fine but you'd probably be just as good with 2", depending on your modifications.
A well tuned exhaust system should help scavenge the cylinder charge. Going too big on your exhaust size reduces the system's ability to efficiently move the gases out of the system.

 

I think Eric is still the only source for an exact reproduction system. They are generally reproducing these several months behind the date of payment:

Muscle Car Exhaust Systems - Gardner Muscle Car Exhaust Systems (gardnerexhaust.com)

 

Hi,

The factory system/Gardner is 2 or 2-1/4" and the tail pipes neck up to 2-1/2" only in the chamber section, Walt V use to make tailpipes stock or custom ones that were 2-1/2" the whole way, not sure if anyone else makes them as heard he retired.

My 65 Cutlass running a 455(450hp) is going to be 2-1/2" with a set of Walt's larger tailpipes.

3" might have some issues getting around everything over the axle and wouldn't have the same look as factory pipes unless someone is making a larger version of the chamber style.

Here's a picture of the larger tailpipes on my car:





doesn't look any different from the outside but no neck down above axle like the factory or Gardner system




Regards,,
Jim

 

As of the beginning of 2021 I could not find anyone that had resumed production with Walt’s tooling and work. The Parts Place began offering a much cheaper system but it does not have the factory chambered pipes. I could not find chambered pipes offered except as a part of Eric’s complete system.

 

thank you. when we got under car we saw Flow masters in place so we left that alone. ran new 2 1/2 from there to behind the rear wheels. feels/sounds much better now. thank you

 

good thoughts. we went 2 and 1/2. good blend of rumble and improved air flow. thank you