Help on 408 build

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836.3 - swept
63.5 - head
11.2 - gasket(8553)
20.5 - piston
1.0 - area above rings
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932.5 - total
96.2 - total minus swept
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9.69 - CR
 
The CR calculator is still up and loaded from this AM LOL

I am getting 9.7:1 for:
  • 4.00" stroke
  • 4.03" bore
  • 64 cc head chambers
  • .049 thick head gasket with a 4.18" bore hole (That's the spec for the 8553PT Felpro kit head gasket
  • 21 cc dish volume (I add a bit for the crevice space down to the top ring)
  • .000" deck clearance
DCR with that piston and your present cam is 7.9:1 installed at an ICL of 108 degrees.

NO worries whatsoever over 1 gram.. that is down 'in the noise' for a street engine. 10 grams... I can go either way; no 'flaming' from me on that matter. It's generally agreed that stock SBM's, including 340's, had a factory tolerance of +/- 20 to 30 grams for all the balance work. It is fortunate to have a substitute piston to be THAT close!

And no worries over re-examining this... it is a lot to absorb and weigh back and forth.
 
this is with his home ported heads or new ones?\
if AL he's good to go
If Iron, well with either he has to sneak up on the tune
or take the chambers out to the bore-not the gasket if he can DIY
this combination should pull real good
still 4.11s
 
Those numbers are for either head and this suggested piston. His open-chambered iron heads have apparently been shaved quite a bit down to 63-64 cc chamber size, which is right where most AL heads are for chamber size.
 
Hopefully in a few weeks I’ll post a video of it running. Pistons are paid for and on order. No going back now lol
 
So good news. Got the engine running yesterday with the new pistons and today I got the timing done. Took it for a ride. Pinging is gone and I’m happy with the end result. Still some fine tuning but I’m happy the compression is now in a controlled zone that I can run on pump gas
 
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