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4.7L Exhaust. 2.75-3"?

XJoshua

NAXJA Forum User
Location
Pueblo, CO; USA
Well I was looking on Dino's site and saw that for my expected HP range i should be running 2.75" exhaust on a 4.7L. Now im assuming that chart was made for stock heads. So with me having a 4.7L with SBC valves and 2000 intake ported and head running tuned headers would pushing to 3" be a waste of money. Ill be running a universal hiflow dynomax cat and super turbo muffler because i love the sound and its cheap on the wallet.

I dont think anything else will have a play in the sound. but ill be running 32s with 4.10s or 4.56 havent desided yet.
 
That sounds way too big. I don't think you'll take advantage of more than 2.5"?
 
I'm with Cal on this one. Maybe 3" if the motor could turn hi rpm...but no.
 
LOL Cal...I'm a old bike racer....high rpm to me begins at 10K.....:eek:
 
I think high RPM starting around 5500, but 8 cylinders instead of 2 or 4, so I guess we're talking about the same thing ;)

I put 2.5" exhaust on my XJ with a bored throttle body and borla header (granted, not stroked) and noticed *no* gain.

Vintagespeed has a 4.6 in his MJ with stock exhaust and it will spin the tires until you get bored with the idea.

The 4.0(/4.6)'s strong points are in the 1200-3200 RPM range, and your not going to push that much exhaust through.
 
I followed Dino's advice about putting a 3" flange on the header for a 4.7 stroker. 3" pipe all the way back and then a 2.5 reducer. Put a flowmaster 2.5 to 2.5 muffler Delta 40 muffler. Then 2.5 out the back.

SOUNDS LIKE POOOOOOOP

tinny sound..popping and bad.

The theory was a 3" crush bent will reduce to 2.5 roughly. And consider a 5.2L v8 motor is using a 3" to 2.5" pipe stock from the factory. Usually opened up to a 3" all the way back. So in theory, the 3" to 2.5 should be good for a 4.7L motor...but mine sounds pretty bad.
 
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