a few l03 questions
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a few l03 questions
i'm trying to work up a compression ratio for my l03 with vortec heads installed. problem is i need to know
1. piston: dished or flat top? how many valve reliefs
2. how for down the bore is the piston at TDC
3. stock head gasket bore and thickness
4. stock combustion chamber size (i believe it to be 58cc)
or, does anyone know approximately what the compression ratio would be on a 305 with vortec heads? stock is 9.3:1, that much i know. ideally id like to keep it above 9:1.
the setup i have in mind involves a pair of vortec heads with a GMPP TBI intake. an lt1 cam, or a close approximation to it. the lower half of a 454 throttle body unit. im gonna go after a set of roller rockers. basically my end goal is +\- 300 HP and better than 300 ft/lbs. its a daily driver.
any and all input, tips or advice is welcomed and greatly appreciated. i just want to make sure all my homework is done before i get into the motor. i dont like suprises
1. piston: dished or flat top? how many valve reliefs
2. how for down the bore is the piston at TDC
3. stock head gasket bore and thickness
4. stock combustion chamber size (i believe it to be 58cc)
or, does anyone know approximately what the compression ratio would be on a 305 with vortec heads? stock is 9.3:1, that much i know. ideally id like to keep it above 9:1.
the setup i have in mind involves a pair of vortec heads with a GMPP TBI intake. an lt1 cam, or a close approximation to it. the lower half of a 454 throttle body unit. im gonna go after a set of roller rockers. basically my end goal is +\- 300 HP and better than 300 ft/lbs. its a daily driver.
any and all input, tips or advice is welcomed and greatly appreciated. i just want to make sure all my homework is done before i get into the motor. i dont like suprises
Supreme Member
Joined: Sep 1999
Posts: 7,072
Likes: 13
From: Philly, PA
I'll take a crack at it....
1. Slightly dished, 4 valve reliefs. About 8-10cc worth of total dish.
2. .025" factory spec, same as almost all SBCs
3. If anyone really knew the answer to this we'd all be rich. I've always assumed it's about 5cc worth of head gasket volume but I don't know for sure. Certainly thinner and smaller than typical .039" thick 350 "rebuilder" head gaskets, but by exactly how much I don't know.
4. 58cc spec.
Add all that up and you'll drop right on top of 9.3:1.
Swap on a set of Vortecs without changing anything else and you'll be just shy of 8.9:1. I'm using 62cc as the chamber size for Vortecs since those who have measured them out almost always come up about 2cc smaller than their published 64cc spec.
1. Slightly dished, 4 valve reliefs. About 8-10cc worth of total dish.
2. .025" factory spec, same as almost all SBCs
3. If anyone really knew the answer to this we'd all be rich. I've always assumed it's about 5cc worth of head gasket volume but I don't know for sure. Certainly thinner and smaller than typical .039" thick 350 "rebuilder" head gaskets, but by exactly how much I don't know.
4. 58cc spec.
Add all that up and you'll drop right on top of 9.3:1.
Swap on a set of Vortecs without changing anything else and you'll be just shy of 8.9:1. I'm using 62cc as the chamber size for Vortecs since those who have measured them out almost always come up about 2cc smaller than their published 64cc spec.
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