Exhaust change. How bad will it be?

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1968FormulaS340

1968FormulaS340

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I have a 68 Formula S 340, 4 speed with 3.91 rear. Engine mods are..... Ported X heads, balanced, 11.5 compression, Edelbrock Victor 340 intake, Holley 750 puddle dumper, Crower Street Roller (#31406 lobe center 112?, advertised duration i&e 290-294, duration @ .050” 251-256, lift .550-.555.) RPM range 3200 to 7200, redline 7800+.

I run headers and 3” exhaust with DynoMax Super turbo mufflers.

My question is...I want a more stock look under the hood so I am thinking about putting the stock exhaust manifolds (I have the original 340 HP parts) back on with the full (tail pipes) TTI, 2 1/2” Xpipe system. How bad will this be with my above combo.

Part 2. I know the exhaust change will hurt power, but what kind of a loss will I be looking at if I also put the stock intake and Carter AVS back on.
 
In short. no. I dont think the calibrations, or even the amount of calibrations a stock carb gives you will be enough to make this even worth thinking about. Get another engine if you want stock looks. I would suggest a large small block..416/408, and a cam chosen to run with factory manifolding. The long stroke will keep things very usable, even more sneaky, but you'll have much more usable power on tap.
 
I'd have to agree.Your motor is a large air pump.Everything you've done was geared toward moving more air & fuel through the motor.So going backwards would really choke it down big time.Now you can still make plenty of power with stock type parts,but you build the motor with these parts in mind.With that huge cam & ported heads,you'll be bringing in in more air than the stock manifolds can extract.
 
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