bore 4.08
stroke 3.78
cylinder hv 67 cc c3ae c
effective dome volume +10 trw l2291f +30
here is the problem I don't what to enter deck clearance 0.05=9.39 cr and 0.005=10.32 cr 9.39 would be ok don't want to go over 9.5
compress gasket thickness .041
Any hep with correcting my numbers thanks Emery

631/2 galaxie XL 390
Rangon red
F-427 intake
C3AE-C heads
C0AE castiorn headers

hmmmm, 67 cc chamber? i think your over 9.5

You will have to mock up what you have and see how far the pistons are below deck. It's just one thing that you'll never know, since the block could have been decked a million times in its life.

Theoretically, with a standard FE deck height (10.170"), you should be at:

10.170 - (3.78/2) - 6.490 - 1.776 = .014" below deck. However, as mentioned earlier, your block could have been decked that far or more over its life time.

Brent Lykins
B2 Motorsports, LLC

deck clearance 0.05=9.39 cr and 0.005=10.32 cr 9.39

.05 = fifty thousanths. Not likely.

.005 = five thousanths. most likely.

You need to measure the piston in block at top dead center to know. Also you said + 10 cc on piston volume. Is it a pop up dome piston?

57 Club Sedan
428 CJ
TKO600
Currie 9+
Tru-trac
Caltracs

no I think +10 cc is what you add to cylinder volume -10cc would be a dome.

631/2 galaxie XL 390
Rangon red
F-427 intake
C3AE-C heads
C0AE castiorn headers

Plain old TRW/Speed-Pro four eyebrow deal. It'll likely end up somewhere between .010 and .020 below deck unless the block has been whacked a ton. You're gonna end up around 9.75ish if I were to guess, and it'll be just fine. Ten gazillion 390s are running up & down the road with those pistons - they were in the top 10 sellers for TRW and Speed-Pro for the entire 12 years I worked there...

Barry Rabotnick
Survivalmotorsports.com

It's interesting how Ford rated compression ratios back in the day.
The 4V 390 was listed at 10.5 and the 2V was listed at 9.5:1.
When measured the 4V ones were close to 9.5, nowhere near the advertised 10.5
The dished 2V pistons were closer to 8.5:1