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2.25" vs 2.50" exhaust system

cmayna

cmayna

DILLIGARA?
Donator
I am ready to take Shag in for its exhaust system. I had my muffler guy come over to see what I have and he feels comfortable installing a 2.25" system but thinks that 2.50" pipe especially between the Zbar and the steering box is going to be tight. Might have to dimple that area.

So for street application (351c, 4v heads & stock manifolds), can I get by with 2.25" ?
 
I bet you could "get by" with 2.25", but 2.5" would probably be better.

Then again, what's a few HP... you probably wouldn't even notice the difference in the seat.
 
If I thought you'd ever take it to the track, I'd say find a way to shove the 2.5" in there. Since I don't think you will, it won't matter at all ... go with the 2.25"
 
What John said! Not like you'd notice a few less ponies (on the street).
 
Craig, I dont know much about your motor but it is always best to try to reduce backpressure with your exhaust system when trying to make hp. The 2.5" pipe will have a "deeper" and slightly louder sound. If the car is just going to be a cruiser then a 2.25" system will be okay but it will cost you hp. If making the most hp you can is your goal then a 2.5" system is the smallest I would run. What mufflers are you planning on running? If you're going to run a restrictive muffler that wont flow as much as a 2.5" pipe anyways then the point is mute.
 
I'm planning to run Dynomax's Super Turbo mufflers which do come in both 2.25 and 2.50 systems. I am afraid that if I attempt 2.50, I might need to have the pipe that goes between the steering box and Zbar's lower arm, slightly crimped inward for clearance. If this was needed, would going 2.50 still be worth it?
 
Keep in mind when the muffler shop bends any size pipe it will be slightly pinched... unless they have a mandrel bender. I looked throughout the SF Bay area, and I couldn't find a shop with a mandrel bender.

So if you start with 2.25" you'll have some pinches in the pipe, especially when the pipe is bent over the axle tubes, which will be smaller than 2.25". I say you might as well start with the larger 2.5" pipe, who cares if there's a minor pinch around the z-bar... you're gonna have some pinches in other places, too.

my 2 cents.
 
The place I used in Daly City near the cemeteries had a mandrel bender. They gave me a great deal when I told them that, I knew a guy, who knew a guy (if you know what I mean) :ep

Anyways, I would also go with the 2.50 if you can squeeze it in there. Hell, my single exhaust is a 2.25" for my little six.
 
What is the outlet size of the manifold. Going much larger than that will be a waste. Are you planning a merge (X) pipe? It makes a difference in low to mid range power and does not hurt the high end.
 
My vote is for the 2.5" exhaust. Those Clevelands have large heads for a reason, they like to breathe! If this were a 289 or 302, I'd be all over the 2.25" for convenience. I think you'll be holding your motor back with 2.25" exhaust. Have you given thought to the Magnaflow Stainless kit? I know it's set up for long tube headers but for the price it really can't be beat. All of my local exhaust shops wanted more for a 2.25" aluminized shop-bent exhaust than the 2.5" stainless mandrell bent kit would have cost me.
 
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