i have a pair of 5.7 vortec's with flat tops,stock roller,air-gap,600edelbrock,closed cool,i use valvetech gas
my math says 9.9to1

....has any body run anything like this.....

give me some detonation horror stories

should i go to a longer cam with wider LSA or should i be ok

looking for efficiency and no quench lectures please

dirtyplumber:
Are your vortec's automotive engines or are they from Merc. etc. If your pistons are stock your compression ratio is actually 9.5 to 1. This compression should not be a problem even with 87 octane fuel. If your vortec motors are 1995 or later they have hardened valve seats and should not need valvetec fuel unless you prefer it. If you engines are marine units the cams are a little larger specs than automotive units already. If you need more power I would suggest talking with a good cam company like Comp Cam or Crane and get their recommendations based on how you will run and use the boat.
Hope this helps,
Raylar

raylar ;my vortecs have real flat top 4VR pistons (030.over)not the slight dish that come with all vortecs (marine being high silicon)automotive are regular cast, and stock marine roller cams 196-206/.431".451"/109
valvetech is just what they have at my marina (93 octane)the owner of the marina runs twin 454's with 8-71's
i'm hoping i'll getaway with 28 to30 deg. of adv. total
delco EST wich =6 to8 deg. of adv. initial
probably won't idle to good with much less
surely somebody must have stuck some flat tops in a vortech

I have flat tops on a pre 86 block and installed vortecs on a sbc. The cam I chose is a comp 270h. Runs stromg with a total advance of 32. This is what Dennis Moore recommends.

I am going to be putting vorecs on my '97 SBC. I am leaving the standard pre vortec flat pistons. I am going to use the GM head gasket (12557236) that is used on the vortec marine engines. It is a little thicker than some others (051). I am not planning to change the cam. Would anyone know what my compression be?

And how do I calculate it?do I take the measured compression, subtract 15 and divide the difference by 15?

DonM

don ,if you look again your pistons probably have a slight dish unless they are pre 1986