84StarshipBerly

So I'm building my first motor and I'm absolutely exploding my brain trying to figure out all of this with Static and Dynamic compression ratio and my quench.

My parts:
Sbc 350 .60 over
Eagle SIR5700BPLW rods
Trw l2304 060 piston which seem to be speed pro now with the .100 dome
stock 350 crank balanced to rods and pistons
I-037 world/dart sportsman II heads with 64cc chambers
I'll be using a comp XE284H-10 cam

So my issue is is calculating compression ratio and getting the quench right and still be able to use 91 octane gas. My piston sits .030 in the hole and with a .028 head gasket I come up with 10.99:1 static compression using the summit calculator and .058 quench. Looking online I see that .060 quench seems to be the maximum but .040 is where you want it apparently. Using a dynamic compression ratio calculator I get 8.23:1 dcr. So would all of that be safe to run and have no problems with pinging with correct timing or am I screwed and I have to dump even more money into this thing. I'm not entirely sure what compression ratio is safe for those heads since I see all types of different answers. Any help is appreciated.

sofakingdom

iTrader: (1)

Is that MEASURED? Usually with that kind of pistons it's more like .045" down. Often more. Stock, the clearance is around .025" +.015" / -.000", and those pistons add the .020" of "rebuilder" clearance. So, yeah.

Given these parameters:

4.060" bore
3.48" stroke
64cc chamber
2.4cc dome volume
.045" deck clearance
.028" gasket
Cast iron heads

I come up with 10.5x:1 compression. Not pushing it too hard on pump gas. That's WWWWWWAAAAAAAYYYYY too much cam though; or more accurately I should say, since there's no such thing as "too much cam", only "not enough motor", that that's not enough motor for that cam. I'd strongly urge you to dial it back at least 1 step, which would be the XE274. Maybe even 2 steps (XE268), epecially with those highway gears (3.42) and if you still have the stock converter.

Yes your quench is poor (very large) but since your compression isn't trying to push the envelope it's not really a big deal. You'd do better to worry about ANY AND ALL sharp edges in the chambers: radius the top of the bores, grind a chamfer where the head chambers meet the deck, back-cut and radius the valve margins, etc. Anything you can do to avoid sharp edges or thin metal in the chambers will help, always.

84StarshipBerly

Yes I was using a bridge and dial indicator in line with the wrist pin and got .030" pretty consistently. I was told that cam would be okay especially since I would put a 3000 or 3200 stall converter in as well. My heads also have the comp 986-16 springs on them as well so if I decided to change to the cam that's a step down would I also have to change the springs?

Fast355

iTrader: (2)

I 2nd the cam being way off. That cam will want more like a 4,000 rpm converter to get with the program and will not really wake up until past the point the heads are strangling it. Step back to something around 226 @ 0.050.

sofakingdom

iTrader: (1)

No. They'll be fine, if set up properly.

84StarshipBerly

Alright thanks! I'll keep all this in mind. It at least gives me some relief knowing all of this so I really appreciate it.

tom3

I'd worry some about piston to head clearance too. The chamber shape might not work with those pop-up pistons?