2 questions.

First, if I puchase some vortec heads and want to apply them to my 305 HO, how much should I have milled off?

Secondly, if I later upgraded my 305 to a 350, how would that affect my compression ratio?

Thanks.

 

It'll bump your compression pretty far up on a 350. You'll need to use thick gaskets and pistons with a slight dish (you might get away with 4 valve reliefs if your gaskets are thick enough) to keep it reasonable. I'm not too sure about how much you'll need to shave, but you need to shoot for 58cc chambers.

-Mark W.
'88 SC Camaro w/ 305 TBI

 

What size of chambers do the vortec heads have, and how would I find out?????

Thanks again.

 

The Vortecs have 64cc chambers. I had a Car Craft issue where they did a 305 build up with the L31 Vortec heads...I don't remember where that magazine is, or how much they shaved 'em. Go search the archives, you might be able to find something there.

-Mark W.
'88 SC Camaro w/ 305 TBI

 

I found the Car Craft issue on-line. They milled 'em .045 and said they got just about 10:1 with .015" thick gaskets. That means they were right around 58cc chambers, maybe just a little less. Here's the article...
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Parts list

-Mark W.
'88 SC Camaro w/ 305 TBI

 

If you mill some off of the head, are you not running a greater risk of the valves hitting the cylinder?? I am thinking of doing the same thing.

 

most engines i've built, with stock head deck thickness or even milled up to .03 using a zero deck block and flat top pistons will have around .25 valve to piston clearance. i always dummy up my engines with out gasket so you could add .04 to that. i wouldn't use a shim gasket ,you need a very good finish to make one seal. i'd go with a composition type gasket. i use fel-pros and spray them with a coat of k&w copper sealer and never had a leak.

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