what grade of fuel will these DCR's require? thanks...

7.543 / 8.72 static CR

8.403 / 9.74 static CR

9.137 /10.6 static CR

 

These estimates are based on quench chambers. An open chamber motor will need higher Octane.

 

i didn't think to mention, open chambers.

 

The 7.543 DCR is probably OK with 89 Octane even with open chambers, but I would be worried about a DCR of 8.4:1 with open chambers, if I wanted to use 93 Octane pump fuel. The 9.1:1 DCR should be OK with 99 Octane with open chambers.

 

89 with 7.5 (dcr)... closed head?


(most oz 2v heads combustion chamber is actually 55cc though reported as 58-62cc) I measured mine @ 56 after polishing)
so most cr will be higher than calculated with those heads.

Tim had one with higher dcr than mine with his pistons and cast oz 2v heads that burned premium pump under load. Mine isn't really tested on pure pump yet but is about 8.3-8.4 dcr with the same set up as tims but supposedly a little lower dcr and is running ok thus far on 91 with some lucas octane boost...after chatting with tim i'm expecting it to run ok on 92 which is the highest pump i've found here. I've even considered putting this engine in my daughters car if it does run well on premium and building a different propane version for my truck... wasn't expecting a 8.4dcr to run on pump and if it does i'm not going to waste the 'most excellent' quench on propane..that would be stupid beyond even what i usually do.

anyway,then theres the temp, vehicle weight, polishing chambers, towing or not yada yada. and the difference in pistons...ie badger vs tim's flattops.... badgers, from what i've read, has a a detonation profile like listed above...what about the better pistons?

So I guess I'd agree if were talking low risk for detonation and not pushing the envelope... someday we will have enough info to take this discussion to the next level.

All of this (what i've said) is suspect and what i've read or witnessed thus far.