Engine size vs reversion.
 

Is there a relationship? Example my 498" BBC is running a 272/280 duration @ .050" cam on a 112+4 installation. My exhaust pipes exit completely underwater which makes it very quiet which I personally like especially with BS noise laws. Anyway with my 498 there is no problem with reversion with the exhaust I am currently running. Would the same or basically the same cam be reversion free in say a 540" or 572" using the same exhaust? Does the larger motor pull more back on overlap and does the extra flow leaving the exhaust basically keep the reversion away? I hope I am stating what I am thinking clearly.:rolleyes:
Thanks,
Craig

Dang, no answers! Well with a larger motor the vacuum signal to the carb will be better than a smaller motor running the same cam. Does this also mean there is more vacuum during overlap to pull back the exhaust, or will the added exhaust flow / velocity offset the increased "exhaust vacuum"?? I guess it is one of those things you won't know until you try it out.

NO SIR VETTE WITH THE SAME SIZE CAM IT WOULD BE LESS THE LARGER THE ENGINE ,sorry about caps it was stuck !!:D

Bobby,
That is good to know and kinda what I thought. I try thinking things through and sometimes come up with some off the wall thoughts about what may happen. Thanks for the response.

Yes I do the same thing ,,brain fade at my age !!!:D :D

On your cam specs; Did you mean that the cam is 272/280 minus 50* or 272/280 @ 50*? If it is the latter then that is a LOT of duration! I didn't know you could run a cam with those specs in a boat WITHOUT getting reversion. Just curious.

I agree that those duration #'s are astounding. This is an important topic. Could you double-check them?

The duration I mentioned is not a misprint. The specs are @ .050" lift and I currently do not have any reversion problems with the 498" motor and and the CMI exhaust I am currently running. They exit about 6" below the water so they are real quiet at idle and at the same time because of the drop there is a lot of dry pipe which keeps the reveresion at bay. The reason I ask about the larger motor is because my 498" is running 13.2:1 compression and $3.00 gas. If I go to a 572 or 598 I can run 10:1 comp and use basically the same cam on pump gas and make close to the same amount of HP as the 498 is now running 110 octane.

Just curious....if your gross cam lift duration @ .050 is 272/280 what is your running duration?

Duration @ .020" lift is 308/316, and the duration @ .050" lift is 272/280. Advertised duration isn't even listed on the cam card. Lift is .714" and valve lash is .024" hot.

WETTE VETTE, if you go up an cubes, with no other changes, the power curves will be as high, but at a lower rpm. If you want to do this, you really need better heads. If the heads are up to the task, your cam will probably be good, but if the heads are not good enough, your top speed may drop with a noticable increase in low speed torque!!!

Blown 1500,
I figured some CNC heads will be needed to feed the 598". I still want to turn 5500 to 6000 RPM so I still may need to tweak the cam grind a bit. I will definately talk to you about the AFR's when I get to that point. Only downfall right now with the AFR's is I already have the bolt on Jesels for the Dart heads. Talk to ya later!!