.159

My engine guy says the oem piston is sitting .159 below the deck in my 74 250 block.

Ive heard .090-.150 range is common.

Should I believe his number or mock it up and check it myself?

This guy is experienced and does a lot of engine building, he has a very good rep.

Able to get any measurements on disassembly?
Can't figure on paper as easiest, 1st best guess?

As long as he isn't measuring into the dish. It should be measured at the edge near the pin. Mine was .108 fyi, appeared to be virgin 1970 250. Trust but verify his methodology, hopefully he's not offended. If he is, find another machinist.

This is a virgin 1974 250 block with a C9 casting.

3.71 bore
3.92 stroke
5.99 rod
13cc dish piston 1.5CH
.050 head gasket
58cc head
.049 down in the bore

= 8.85:1 CR

If his numbers are off and the pistons are .029 in the bore the CR = 9.18:1, .009 in the bore the CR = 9.54:1

I may not have to mill the head, so I can use a thinner head gasket.

So there is a little room to work with, if I can find 6 5.99 rods.

The .159 from the block deck to top of piston sounds about right to me, as the earlyier block's had less. My 77 250 had even more than this. Good luck

X2 .159 is common on a 250

Howdy Georgia and All:

"Should I believe his number or mock it up and check it myself?"
Yes, and yes.

As my Dad used to say, "Measure twice, cut once. And wear will make the tear down measurement even greater. Once you get new parts and clean, machined surfaces measurements will tighten up. So, Critical- remeasure on assembly.

Adios, David