Would the addition of Vortec heads allow me to bump compression up a bit from the lowly 9.3:1 to say like 9.8:1-10:1 or so with out concern of detonation destroying anything? I know it would be problem with cast L98 but what about the Vortec 062 or 906's?

 

As long as you're adjusting compression via the head gasket, no problems I can forsee.

Thinner gaskets make for better quench area management, resulting in less susceptability to detonation...and with more compression.

Cutting the heads and then using fat gaskets is a no-no.

I ran skinny 0.022" copper head gaskets w/ my AFR 190 heads, angle-milled to 58cc chamber size. Plenty of PROM tuning involved to get it dialed in, but even running a fairly hot Vette-based spark map it was a happy camper on 93 octane. Cranking down the advance closer to stock F-body specs (but not all the way there) got me knock-free on 89 octane.

 

Actually most engine builders will bump the compression slightly when using a modern style heart shaped combustion chamber like the vortecs have. They promote alot of swirl which gives you a faster burn, therefore less timing is needed for optimum power and more compression can be used. Most new heads now a days have this style combustion chamber. I know of several engines around here with cast iron vortec heads with 10:1 or a little more compression and running on pump gas just fine. Although you have to have good knowledge of tuning to make it work along with a good camshaft profile etc...
I have a 406 in my Monza that has 10.6:1 compression with World cast iron heads that have the old style combustion chamber and I have the engine running on 94 Sunoco just fine with carefull tuning, I believe with the more modern combustion chamber I could get away with either more compression or less octane gas depending on which way I wanted to go.
If you go with an aluminum head with the new style combustion chamber you could even go up roughly another point in compression and be safe with a good tune. Most engine builders will stay conservative though to cut down on engine damage due to poor tune up etc....there are other variables like camshaft profile, intake design, etc...that will have an impact on octane tollerance...Anyway I hope this helps, I am rambling again. I am sure there are alot of other people on here that have done this. Goodluck,,Larry.

 

Most likely stay with a stock style cam, nothing bigger then a 220 dur. and nothing higher then .500 lift, just good and torquey.

 

I don't understand how you intend to increase the compression with Vortecs. Or with thin head gaskets.

Vortecs have the same chamber size as L98 heads. L98 uses steel shim gaskets from the factory.

The only way Vortecs could raise compression is if they are milled.

 

Awww. Then new pistons it would have to be.

 

The 9.3:1 was the result of 4 valve reliefs plus a slight dish, for about 12cc total, IIRC. Flat tops with 4 valve reliefs would be about 5 cc, which would raise you up above 9.5:1. Any more than that would require some shaving.

It makes sense to deck the block and then use a head gasket of appropriate thickness for .035-.040 quinch height. With flat tops, you should be at around 9.8:1 with 64cc chambers and 4.030" bore.

 

Sorry, I did not realize you were wanting to raise the compression soley by replacing the heads, I thought you were building something from scratch. Just for the record and for giggles, a buddy of mine that runs a machine shop built a little 355 for a friend of mine with old camel hump heads, it was a flat top motor and he made 11:1 compression with that by milling the block until the piston was actually sticking out of the top of the block slightly. Everything was very close and it took carefull machining but he wanted the flat top piston due to the fact that they allow the heads to flow better, no dome to disturb flow in the combustion chamber. He could of made that compression easier with a dome piston but it would have cost a little power. He stuck the motor in an 84 Z-28 with victor jr. intake, 750 dp, 4.56 gears, and a 350 turbo and the car would run 12.0's at 114. Kinda neat, just thought I would share. Sorry for rambling, Larry.