Well I'm getting closer and closer to finishing up my 302 and getting it in my 67. One thing I am unsure of is the size exhaust needed for the V8. I currently have 2" exhaust all the way and was curious if that is too restrictive for the 302. I'd like to be able to keep the exhaust in since all I would need is pipes from the headers to my x-pipe, but if not possible I will replace it.

 

I would say that's ok for a very stock 302..Any mods and I would go at least 2 1/4 or 2 1/2..
How restrictive your mufflers are and how badly crimped the pipes are at the bends will also make a huge difference in how free flowing the system is no matter what size it is..

 

Well the 302 will have port matched stock heads, weiand intake, edelbrock 600cfm carb, nonstock pistons, and HEI ignition.

 

I'd shoot for 2-1/4".

 

Are the pipes mandrel bent or crush bent? If they're mandrel bent they'll look the same size at all the sharp bends (over the axle) and be smooth, if they're crush bent they'll have ripples at the sharp bends. Mandrel bent will be 2" throughout the whole system and flow well enough for a semistock motor, crush bent will be as small as 1 1/2-1 3/4" at the bends which means your whole system can only flow that much.

If you're stock heads haven't been ported they won't flow that much better, port matching is a good idea but if they still have all the emissions humps, slag and sharp corners they still won't flow any better than stock.

If you're into doing it yourself you can get flowmaster tailpipes (mandrel bent 2 1/2") kits for ~$130 and put some low buck turbo mufflers on if you think your 2" is too small.
Jon

 

My 2" exhaust isn't even a year old. The pipes the guy made me are mandrel bent, but the premade exhaust pipes from mufflers to tips are crush I believe.

 

I would go with 2.25. Hopefully you can still use your tips. Have them expanded to fit your new pipes.

Put your new/used pipes up on craigslist. I bet you can find someone with a bone stock V8 or an I6 that will buy them.

Are you going with turbo mufflers again or something like Magnaflow or Ultraflo?

Having said all that. The 2 inch exhaust would work. The big block cars came with 2 inch pipe from the factory if I remember right.

You could always run it for a while and change it later.

 

i'd go with 2.25" as well, however I bought stainkless boxes, strainless headers so I want to have the tubing stainless as well. And I have an awful problem sourcing 2.25" stainless pipes in Ireland, probably have to get them from UK.
So if you want to go stainless check around if you can get tubes and bends in 2.25" size. if there's a problem, go with 2.5". if you go for steel tubing 2.25" should be fine. It is for me.

 

I am running 1.75" pipes on my 55 Lincoln with a 341, and Mitch is running 1.75" pipes on his Falcon with a mild 302, your 2" pipes are MORE than adequate for your 302.

IMO The NEED for giant pipes has been greatly exaggerated by the aftermarket exhaust companies and the fast and the furious crowd. (3" pipes on a Honda add 96 HP)

Your 2" pipes will work just fine, and they are CHEAP, cheap enough to at least try out before you wack-um off.... You will be happy with the way they perform and IMO "smaller" pipes just sound better...

 

I vote for the Magnaflow 2.5" stainless exhaust kit. You can get the kit for a song compared to what some exhaust shops will charge to make an aluminized kit for you. What happens if you opt for the 2.25" exhaust and then in a year or two you decide to drop in a stroker motor? I say go with a size that you won't outgrow in the near future, and the stainless will last you forever. Talk to Dan at Performance Peddler and mention the VMF (sold hundreds to members of that site) and ask if the $350 deal is still possible. The Magnaflow kit has an X-pipe and is made for long tube headers, so you may have to have a shop make some extensions to the manifolds if that is what you have. I would look into getting headers if you haven't done so already, because porting heads and installing a larger exhaust will still have the restrictions of the manifolds.