Can I please get some help with a street build 383.

Bore-4.280
Rod-3.375
Piston-L2315F

The short is together with a flat top piston and it’s .008th in the hole.

Cam is an MP 272 adv & .455 lift & 112 lobe

915 Heads are slightly ported they flow 233 @ 500.

Db4p slightly ported single plane intake

Going to run stock manifolds.

915 Heads are at 83cc after valve job.

I was planning on using Felpro .039 head gasket 4.50 bore

What is a good compression range for this combo? Not sure if I should leave the heads at 83 or cut them.

Street car, 4 spd 3:91 gear

Hi Beep , I did a 69 RR with same cam + pistons + manifolds . 727 Auto with 3.55 sure grip . Block decked .020 , pistons popped OUT .010 , and I used 906 heads with Fel-Pros. The heads CC'd around 88 or 90CC's Stock , Had them cut .040 to get to 80CCs. And to use that 272 Cam had machined down the top of the valve guides boss's down from about 3/4" to 11/16 to give me clearance at max lift . I always said it was finally a 10 to 1 383 after all that work . Ran like a Monster . Ronnie

Thanks Ronnie. For the information.

Have you look on KB,UEM web site to figure out what compression ratio you will have? They have several different helpful formula for figuring out a lot of things on our motors
If not due that next
Knowledge is power

I have checked various compression calculators. If I cut the heads to 82.5 cc that should get me 9.46:1

Why the big bore .039" fel-pro head gasket? Why not the .021" factory type head gasket?

The steel shim head gasket is less expensive, will get you closer to a desirable compression ratio and they work well.
Leave the heads at 83cc and install the correct head gaskets.

I calculate with a .021" gasket at 4.32"gasket bore a compression ratio of 9.8:1

This is a good place to be. Factory was supposed to be 10.1:1

You can shave the heads, but anticipate the possibility of having to shave the intake face of the head and taking some material off the intake manifold (an excellent manifold FWIW). DP4B

Have you checked every piston at .008" in the hole? And, what's the piston to cylinder wall clearance? Are you running them loose or at about .0035" In other words: Do the pistons rock and what's the deck clearance with the piston rocked. .029" piston to head clearance may be a little tighter than you would like... I would run it, but that's me.

my speed-pro catalog states; 9.77:1 with 78.5cc chambers and 8.94:1 with 88cc chambers. this assumes a .039 gasket. a .020" steel shim will have the quench distance too tight, a .039" gasket will get quench distance around .045"; assuming block hasn't been cut. if it were me i'd leave the heads at 80+ cc's with a fel-pro 8519 gasket to run pump gas. i did something similar to what you have but used 84cc 906 heads and seems to have worked fine with pump gas.

9.5:1 with iron heads, a smallish cam like the 272/.455, and pump gas is about the max I'd run on the street.
Been there, done that, had to pull timing back on a 3400-lb Duster with AT & 3.23s.
Still ran great, but was octane-limited (Calif 91) and would ping with the usual performance timing curve.
Had that cam decades ago in a basically stock 383 RR restoration, ran nice & was pretty close to stock behavior.
Nowadays I'd run a cam with more modern design.