compression!
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Junior User
Joined: Oct 2003
Posts: 94
Likes: 0
From: College Station, TX
compression!
ok, i figured this would be the place to put this one.
i'm doing a ground up build for a 351w/408 stroker and want to supercharge with a whipple. i want to be able to run pump gas (92 octane), and i was hoping to put out about 12lbs of boost.
most people i talk to say a normally aspirated motor shouldn't be run over 11:1 to stay on pump gas.
i'v read a few articles that state that the engines 'effective' boosted compression can be MUCH higher than you would normally build a engine for (like 18:1 under full boost), i used this article:
http://www.motorsportsdigest.com/forced2.htm
to figure that i could build my motor for 9.5:1 compression and with 12lbs of boost still only hit 17.3:1 effective compression. this sounds prety darn good to me.
this motor will see light street/strip use in my '91 f-150.
anyone see any problems with this?
i'm doing a ground up build for a 351w/408 stroker and want to supercharge with a whipple. i want to be able to run pump gas (92 octane), and i was hoping to put out about 12lbs of boost.
most people i talk to say a normally aspirated motor shouldn't be run over 11:1 to stay on pump gas.
i'v read a few articles that state that the engines 'effective' boosted compression can be MUCH higher than you would normally build a engine for (like 18:1 under full boost), i used this article:
http://www.motorsportsdigest.com/forced2.htm
to figure that i could build my motor for 9.5:1 compression and with 12lbs of boost still only hit 17.3:1 effective compression. this sounds prety darn good to me.
this motor will see light street/strip use in my '91 f-150.
anyone see any problems with this?
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
Bascially you need less static with MORE boost. Seeing this is a "street" motor, I think you will be okay. You definitely want to watch your a/f ratio. Detonation is a key factor in making it stay together.
I've watched some friends put motor after motor together from playing on the ragged edge with there superchargers.
Larry
I've watched some friends put motor after motor together from playing on the ragged edge with there superchargers.
Larry
Junior User
Joined: Nov 2003
Posts: 92
Likes: 0
ok first of all i say ur risking ur money here a 351 w/408stroker? ok if that is right u have to bore it out what .040?? in this case i would hesitat running it over 2000 rpms letalone a supercharger. i would get the lowest compressin piston i could find and only run about 5 lbs thrust on it if u want it to last more then a year
Moderator
Joined: Jun 2003
Posts: 3,547
Likes: 70
From: Calhoun GA
A 94 Lightning with a built 408 stroker ran a 10.9 in the quater runnin' (i think) 14lbs of non intercooled boost. I would suggest running an intercooler though...much lower discharge temps and you can run more timing. In the end, it's all about the tune.
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