Need Physics help... Boost leak or no?

[TweekedGT]

Ok, I've been having problems with my blower not seeing full boost. I have a 9# pulley on my KB kit but am only seeing 6#'s of boost at my gauge. I believe my stroker should reduce the amount I am seeing at the gauge due to the increased displacement but
I am not sure by how much. Do I still have a leak over and above the potential boost decrease of the 302 stroker motor. Any physics experts out there figure this one out? I know there are some variables but even a rough guess may help. I can't see it being possible to lose 3#'s of boost through a leak, the motor has to play a role somehow. I have increased the displacement by 21CI or 7%, but a 33% loss in boost seems high but is it plausible?

 

[jstreet0204]

More displacement, blower cams, longtubes, high altitude, etc. These things are all going to lessen the boost you see. By the time you add them all up I don't think 3lbs is unusual, since that 9lb reference was made on a stock motor. I see about 2#'s difference just between summer and winter temps here in NC.

 

[TweekedGT]

More displacement, blower cams, longtubes, high altitude, etc. These things are all going to lessen the boost you see. By the time you add them all up I don't think 3lbs is unusual, since that 9lb reference was made on a stock motor. I see about 2#'s difference just between summer and winter temps here in NC.

That's what I wanted to know. I still think I have a manifold gasket problem but not so severe as to leak that much boost. Thanks!

 

[trinity_gt]

Yep, just remember that boost is little more than a measure of manifold backpressure. If you're able to move that much air through the engine your boost reading may drop but you'll still be making great power. It's not unusual to read articles that say after a series of mods (and going from stock to a forged stroker counts as "mods" I'd say...) the indicated boost actually drops but the power goes up.

If you are getting lower boost now and are still within the rating of the air pump (blower), consider increasing its speed with a pulley combo to get you to 9#s again. Sounds like the motor can handle it.