bigfatls6

iTrader: (34)

The engine is a forged 347 with 58cc chambered heads. Can an engine with 12:1 compression be safely run on 93 octane? Also can it be run on 93 octane with optimum timing in it? Or will the timing have to be retaderd? I will be running the f13 cam in it from Futral Motor sports. These are the specs on the cam 230"/232" .595"/.585" 112LSA - aggressive profile with a 2500-6800 RPM range, rough idle.
I would also like to know what is the thickest stock type head gasket that can be used to lower compression? If possible I would like to try to get the compression down to like 11.5:1.

brad8266

iTrader: (23)

I have a similar setup and I daily drive it on 93 octane, tuning will play a big role. It can be done though.

bigfatls6

iTrader: (34)

Are you able to run it with full timing like 28 % or so?

miami993c297

iTrader: (6)

28* of timing at WOT doen't mean the optimum timing for max power, only on some particular cases.

A lot of factors are involved in defining the optimum timing for an engine combo, don't focuse on a specific number, just find what your combo needs...

Christian

slow trap

iTrader: (22)

with a stock gasket and no valve reliefs in your pistons your scr will be 11:6 or so i believe.i had 57cc heads with stock gaskets and had around 11:7 scr and ran a 228r(112+2) with no problems on 93. also that was with a stock bottom end, does your aftermarket pistons have valve reliefs ? that will drop your scr down there to.

brad8266

iTrader: (23)

More timing doers not = more power. Max power occurs when the burn is 14 degrees ATDC, depending on your engine combo and other stuff it could take 18 degrees of spark timing or it could take 24 degrees to get the main burn to occur then, it varies. A good way to tune it is to use a dyno and tweak timing until you make max power while logging no knock.

2001 Pewter WS6

iTrader: (43)

12.1:1 CR here and I run 28 degrees of timing at WOT and zero knock....

allngn_c5

iTrader: (3)

I am glad to read these responses. I am considering a block freshening with new pistons, rings, and rod bolts, maybe forged rods as well. I wanted to up my compression and was wondering if 12 to 1 would fly on 93 octane. I'd be milling my heads a bit further to achieve the desired compression.

bigfatls6

iTrader: (34)

My pistons are probe pistons and have 4cc valve reliefs.

MPHmotorsports

iTrader: (18)

With a good quality tune and 93 octane you will be 100% fine.
Were in about the hottest city year around down here in Ft. Myers Florida and we have many cars running between 11.5-12.2 CR daily driving.
Jeremy

Thimble

iTrader: (2)

And you probably didn't factor those missing 4cc's when you did your compression calculations?.That doesn't add up to 12:1 no how no way.

Stock bore, stock stroke, 58cc heads, -.007 deck, and -4cc pistons, You would be in the 11.0-11.4 ballpark depending on gasket thickness.

jermzz

iTrader: (18)

I plan on 12:1 on 91 if that makes you feel better. Just gotta make sure the DCR is right from what im told.