OK, this is for a 305!

Would it be better to get L31 Vortec heads and have it milled to maintain my compression in the L69 I have...or would it be better to take the L30's and have larger valves put in?

Of course either set, if I picked up either of them, I would have ported and polished and so on.

What are the benefits/drawbacks or either method?

 

GM themselves say that the L31 Vortec heads have more like a 61cc combustion chamber than the 64cc the factory rated them at.

That means you will see, at most, a 1/2 point compression loss on your 305--or around 5 hp. In exchange, the heads will probably add 40 hp.

Does that sound like a good swap to you?

Me too

 

Well that sounds like a good swap, great swap! However, if I can maintain the factory compression of 9.5:1, that would be even better yet.

I know that people have had them honed before, but am curious which is more effective, to hone the L31's or have the L30's machined to fit larger valves.

 

I would be leary of enlarging the valve seat. There is only so much hardened metal around the seat, so enlarging it runs the risk of exceeding the design. Just get a good 3 angle valve job on the L31s.

 

the L30 heads go for about $750 new because they aren't made in great quantities for the aftermarket like the L31 ones are. They also don't have the fastburn looking combustion chambers. They look like TPI heads with a vortec intake pattern. Its probably best to just get the L31s milled. Me, Pablo, and UnderDogRS looked into the L30 heads. Underdog even got some on ebay but sold them again when he got his LT1.

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-Tas
'89 Formula WS-6 made in Van Nuys, CA, U.S.A.

305, TBI, 700R4, P.A.W. 14x3 open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips, Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248)
Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options


[This message has been edited by Tas (edited December 10, 2001).]