302 Compression challenges

It also came with some deep dish pistons which I measured and calculated to be 42.35 CC.

This combination yields 6.43:1 compression according to the Summit compression calculator. I have to assume this combination was never a factory assembly.

I'm debating decking the block 0.020 to get it to the "normal" 302 height, adding flat top pistons and bigger 351W valves and porting it to take advantage of the bigger valves. Then I'll have a 10:1 302 that'll make significantly more power than the current setup.

I'm expecting 300hp with the cam I have.

what is the piston to deck clearance of the short block with the pistons in it now?

can you post up a pic of the piston dish, 42+ cc's seems rather extreme even for 1974

no way that's 42.x, i'll be surprised if it's 10

I like the tool, made my own recently and used it to measure the D5 heads. 

Guess I'll recheck my measurements using the tool.

The measurements I took and the math I had the internet do for me:

My mistake was using diameter instead of radius here:

Oops.

So a rough example could be say 1000cc displacement plus 100cc chamber, divided by the 100cc chamber, thus (1000+100)/100= 11 ... or 11:1 compression. Are you adding the chamber volume to the displacement volume before dividing the chamber volume?

It's been ages since I looked at 302 dimensions. Most pistons stock would be in the 1.6" or taller range IIRC. So a 5.098" rod is about 5.1" plus a 1.5" stroke half length, the 1.60" guess piston height, I'd think the stack to be around 8.2 or very close. That's where the quench is, what's left, hopefully it's under .050" to the piston top for an efficient explosion.

I measured 1.607 pin height on the pistons pictured above.

1.703 - 1.607 =.096 and

1.06 - .096 = .010 below the deck. A reasonable safety margin with a .040 gasket.

Before I bore this 302 to accept my .030 over pistons, How will adding a tenth of an inch taller pistons affect the rotating assembly's balance?

Has anyone done this?

While googling, I found the opposite is a common enough thing that both Scat and Eagle make a crank. I have a worn out (it's already .030 and the pistons are sloppy) '69 351 in the collection. Now I want to build a .060 over 398. 

i'm not saying you can't do it, but i wouldn't even if i had professional quality equipment in good nick available to me. the cost of the learning curve is just too high compared to letting the man with hopefully decades of experience work his magic. modern piston alloys will not survive the loads & pressures involved in pressing the pin into a press fit rod, the the rod furnace is a must! i'm aware there's a way with the right fixture to support the rod and float the piston in the press, but again is it worth the risk? and yes you can do the static balancing yourself & save a couple bones. it's not so much the quality of the scale but the fixture, how it sits on the scale. precision repeatability is the tricky part. dynamic on a complete stroker rotating assy? yeah i'd say that's pretty important, there's a reason they spin it real slow the first time. 

what alloy are your pistons?

yes the rods are weight matched at both ends, in the balance calculation the small end is reciprocating weight and the big end is rotating mass. 

never heard of that piston, probably because it's for a 240-6 LOL but makes sense for a stroker. 

depending upon the cam and valve sizes you may need to cut on the valve reliefs some?

240, 289 & 302

1.585" CH but they're not giving dish volume, what's the crank stroke and what rod are you using?

in what block?