Well, the Mech shop screwed up one of my rods so I can't measure deck clearance until I get the new one back. All of the other pistons are at least .035 down the bore so I think I will be milling .020 off to leave room for expansion and slop at the mains and rods. But I won't be sure until I get the rod back and reassembled to measure clearance again.
I am pretty sure that I will be milling .020 for a C/R of around 9.3:1 static, and with the comp 235 cam around 9.3:1 dynamic in Denver. I did not think that the mech shop would take this long but I guess they are busy.
akadeutsch wrote: All of the other pistons are at least .035 down the bore so I think I will be milling .020 off to leave room for expansion and slop at the mains and rods.
I wouldn't worry about rod stretch too much. At our low RPMs and steel rods they may stretch at most .003". Also, if the bearing measurement adds that much to the quench you will have a problem as it will be breaking down the hydrodynamic oil surface and riding on the bearing itself. What you have to worry about is piston rock at TDC.
FlyinRyan wrote:I'm sorry Dino, but this is not correct at all. The math is fine, but the assertion that a 10+:1 SCR/ 9+:1 DCR combo cannot work on pump gas is absolutely not true.
Proper plugs, proper fueling, proper timing, proper quench....It WILL work, and it will work great.
I wasn't saying it's impossible; just very challenging, and that propane would be a good alternative fuel.
Glad that you're around to give expert advice.
Insinuating it is a "problem" is close enough. Yes, it will absolutely be grumpy on stock PCM without a proper tune.
When the timing advance isn't cranked up a la Spinal Tap , you'd be surprised what you can get away with (I've done combos with as much as 10:1 DCR) on pump gas, and still make awesome power. The truth will set you free, Dino!
I have to make a couple of corrections to my math. First, my DCR will only end up around 7.9:1 with the comp 235 cam. Second, last night I CC my piston dish volume. I was surprised to find a pretty wide variation. The swing was from 12.8 to 13.8CCs. Average was 13.5CCs, a full 2 CCs less than the advertised volume. This slightly raised my CR. Static now = 9.36:1, Dynamic=7.91:1...in Denver at 5,500 feet. I think I'll be fine running pump gas in Denver.
so I can't measure deck clearance until I get the new one back. All of the other pistons are at least .035 down the bore so I think I will be milling .020 off to leave room for expansion and slop at the mains and rods. But I won't be sure until I get the rod back and reassembled to measure clearance again. 
but I guess they are busy.
