Vortec vs stock heads

[scoob4444]

Just wondering the compression difference between the stock heads and the vortec heads on a 350

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[rich weyand]

Regular heads: spec 8.5:1, probably more like 8:1.
Vortec heads: 9.4:1.

[scoob4444]

Thanks

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[LeftysRodandCustom]

Agreed Rich, stock heads have a 76cc combustion chamber, vortec is closer to 64cc

[BADAZ chevy guy]

Vortec heads also have larger intake runners and flow much better. Cam options can be an issue though. vortec valve springs will bind at any lift beyond about .046 lift, unless you have them machined for bigger cam lift. Stock intake manifold wont work either.

[DustyRusty]

vortec valve springs will bind at any lift beyond about .046 lift, unless you have them machined for bigger cam lift.

Do you mean .46 inches of lift?

[BADAZ chevy guy]

Yes. .46 lift. I really hate it when those darn zeros run amock.

[Captkaos]

Heads themselves do not determine compression ratio.  It is the combination of the bowl area, piston volume, bore, stroke and head gasket thickness.

Putting Vortec heads on a generally stock Pre 86 truck will raise the compression roughly a point if you want a generic answer.

Most late 80's 350's had 8.2:1 compression, 305's had 9.2:1...

[LeftysRodandCustom]

While heads are not the only factor in determining compression ratio, they will definitely make a noticeable change when going from one chamber size to another. All should be taken into account, but in my opinion a stock 882 casting belongs in the junk yard if there's a vortec, bowtie, etc. available.