will vortec heads increase compression ratio? if so how much.

 

Depends on what they're replacing, and what's underneath them.

 

there sitting on top of a stock 350 and replacing stock 89 heads.

 

"Stock 350".... covers alot of ground.

The only "stock" heads in 89 were either TBI heads, iron L98 heads, or aluminum L98 heads. The first 2 have 64cc chambers, the aluminum ones have 58cc chambers.

Vortec heads are 64cc. If you don't know exactly what you're working with, preferably by casting number and piston part number, it's near about impossible to predict what it is now, and what it would become.

 

sorry for not making that clear enough. anyways, its a 89 completely stock 350 tbi motor. it has a lt4 hotcam, rpm airgap intake, stock vortecs (stock gaskets), 1 5/8 headers

 

Completely stock 350 TBI...What is this engine from? Assuming the heads are the 193 swirlie heads, they are cast as 64cc.

 

the motor is from a camaro.

 

It is either one of those "magical" 350's, a swap or a stock 305. 350 TBI's were not found in 3rd gens. I would check a few casting numbers.

 

THe L05 was never an option for the F-body, so something isn't lining up here.

Anyway, assuming it is the 193 heads, you should have no real compression difference.

*edit* There is a strange phenomenon that occus upon selling a car. Somehow the 305s turn into 350s.

 

That is pretty weird aint it? When I was f-body shopping before I found my current camaro I musta looked at 4 cars all claiming to be 350's ...you cant argue with the owners either cause they know EVERYTHING. Well, anyway...

Vortecs are claimed to be 64cc but everyone I know who has actually had them cc'd has come closer to 61-62cc's. So, swapping a set of 64cc heads for Vortecs just might raise your compression a little ...not much, but they might.

 

On most stock GM motors a "stock" head gasket means a .015" shim gasket. If you now have a typical stock replacement gasket (.038 to .046") thick and didn't deck the block then your cr would now be lower than stock.
It's all in the details.

I was under the impression that the stock 350 TBI head had a 76cc chamber.

 

The '193's that came on my L05 were claimed to be 64cc by Pace Performance, and some other sites I found that sold the Caprice replacement engine. I didn't measure them myself but I'll take their word since they are marketing those numbers.

 

both 191's and 193's are 64 cc's. I measured them myself.