4.6 DOHC in '67 exhaust questions...

[reenmachine]

I'm having a custom exhaust system made for the 4.6 DOHC in my '67 convertible. The engine combo and the IRS make it anything but straightforward.

I'm using the stock exhaust manifolds. I believe the stock exhaust has 2.25" tubes, and it looks like most of the aftermarket stuff is 2.5".

My question is this:
Is there any reason to go larger than the stock 2.25" given that I'm running stock manifolds on a '00 Cobra DOHC engine with no supercharger or anything?

2.25" pipe would be easier to fit in the cramped confines under the car, but I'll go 2.5" if there would be a real performance gain.

 

[tomustang]

My stock H-pipe is 2.5in. I wouldn't let a DOHC choak itself with a 2.25.

I would love to see your progress considering I have a 67 convertible as well.

 

[mogs01gt]

the stock pipe maybe 2.5in but the inner diameter could only be 2.25.

For sound a little bit more power, I would atleast try to use 2.5, besides that will give you a lot of muffler choices.

 

[reenmachine]

I would love to see your progress considering I have a 67 convertible as well.

I have a stickied thread over in the "Classic Tech" forum. Check it out!

 

[tomustang]

the stock pipe maybe 2.5in but the inner diameter could only be 2.25.

For sound a little bit more power, I would atleast try to use 2.5, besides that will give you a lot of muffler choices.

in 98 the GT's switched to 2.5, the 96-97 years were 2.25. there was no innner/outer difference size. I don't know about the chage in Cobra's but my 98 Cobra is 2.5, i'm sure the anything 98+ is too.

 

[mogs01gt]

in 98 the GT's switched to 2.5, the 96-97 years were 2.25. there was no innner/outer difference size. I don't know about the chage in Cobra's but my 98 Cobra is 2.5, i'm sure the anything 98+ is too.

sometimes there is a difference. on two different advertised 2.5in catbacks, flowmaster and Dynomax, the inner diameter was different for a 94 5.0 I installed them on but I wasnt talking about stock exhaust directly, I was making a general statement.

suprisingly, flowmaster wasnt a true 2.5 inch exhaust pipe.

 

[tomustang]

yeah i heard about that flowcrapster size.