compression ratio?

[dodgedifferent2]

so i have to get some new pistons for my 340 since i had to overbore
i am at .04 over now

I have some w2 heads with 62 cc heads.

I have been playing with compression ratio calculators because i want to keep it on pump gas. The best octane rating around this area is 92. I am thinking i want to keep the compression to work with this octane.
I was told 9-1 or max 9.5 to run 92. If i went to 8 i could run the 87.

Is this true? I always thought 10-1 would work with 92 octane without pinging.

Whats your take?

 

[69.5CUDA]

i always thought if the tim ing was right you could push up just past 10.5...but with the eth in the fuel these days im not sure any more

 

[68R/T]

Timing does have a lot to do with it, but the caveat is, if you boost the compression to increase power, but have to retard the timing in order to run that compression, what did you gain?

Some of the things that you can do to lessen your chances of pre-ignition and still run respectable timing and compression:

Eliminate any possible 'hot spots' in the combustion chamber. This can easily be done by anyone with some patience and a die grinder or a Dremel tool. Run a lower temp thermostat, Definitely electronic ignition. Plus the right cam can lower your static compression ratio and still offer performance gains.

My waGOON is running a 'mostly' stock '68 440, (advertised c.r. is 10.25:1), and I have it tuned to run regular 87 octane. The only mods are the previous mentioned plus a pocket porting and a '72 hi-po 400 cam and composite head gaskets. I realize that there's a world of difference between a 340 & 440 bore & stroke-wise, the 440 being more of a torque motor. So, one other mod I did was replace the centrifugal advance springs with 2 of the lighter ones. That way I'm getting full advance about 2,000 rpm. :huh: