383 quench

[kez2]

find a good compression ratio. I have 69 non hp 383. My pistons are about 67 thousands on the odd side, 1,3,5 7. And 62 thousands on the even side. I think there pretty far in the whole. My heads are 440 source stealth aluminum heads 80cc's. Head gasket 440 source .51 compressed. I'm thinking of taking 20 thousand of the odd side and 15 on the even. Any help is appreciated

 

[kez2]

I'm using flat top pistons as well

 

[Budnicks]

Get a Cometic 0.027" (by like 4.350" bore or smaller)
& make them a bit closer to the bores size 'for head gaskets'
(make sure that 'no ring of the head-gasket 'doesn't go into' the combustion chamber)
stock were like MoPar/Direct Connection 0.018"-0.020" 'compressed' 4.310" bore
'steel shim' style gaskets

but ideally,
for performance based engines, you want about 0.040" of quench,
from the head surface to the top of the piston (gasket included)
yours are already way down in the hole can't get there, with 0.050" gaskets
& piston down 0.065"-0.067" in the hole, that's 0.115" plus, down in the hole
even with a closed chamber head or 80cc combustion chambers,
but you can make it better...

Your giving up (probably min.) a full compression ratio with that combo...
even for our crap gas we have today

 

[68-500]

What pistons do you have? 69 flat top or dish should both be near 0 deck.

 

[1 Wild R/T]

The common 383 2bbl piston has a 1.848 Compression Height...

The spec for a stock 383 Deck Height is 9.98, typically the number is "close" but taller is common & shorter is rare...
Stroke 3.375 x.5 = 1.6875
Rod 6.358
So, 1.848 +1.6875 + 6.358 = 9.8935
9.98 - 9.8935 = .0865

To be effective maximum quench is around .060... Ideally it should be close to .040... Some guys run it considerably tighter.... Some factory engines in the 90's were as close as .025.... That proved to be a little to close....

If your pistons are .062-.067 in the hole your only chance of quench is no head gasket at all...

So, either forget about it or expect to be replacing pistons & decking the block...

 

[kez2]

The common 383 2bbl piston has a 1.848 Compression Height...

The spec for a stock 383 Deck Height is 9.98, typically the number is "close" but taller is common & shorter is rare...
Stroke 3.375 x.5 = 1.6875
Rod 6.358
So, 1.848 +1.6875 + 6.358 = 9.8935
9.98 - 9.8935 = .0865

To be effective maximum quench is around .060... Ideally it should be close to .040... Some guys run it considerably tighter.... Some factory engines in the 90's were as close as .025.... That proved to be a little to close....

If your pistons are .062-.067 in the hole your only chance of quench is no head gasket at all...

So, either forget about it or expect to be replacing pistons & decking the block...

I was thinking decking it atleast. 050 but my engine builder thinks that's too much. He says 15 on one side and 20 on the other. I guess I need to CC the 440 source heads and go from there.

 

[1 Wild R/T]

I was thinking decking it atleast. 050 but my engine builder thinks that's too much. He says 15 on one side and 20 on the other. I guess I need to C the 440 source heads and go from there.

A set of pistons with taller C/H would make it easy... The 1.918 piston if the deck height is .9.98 would be .0165 in the hole.....

 

[1 Wild R/T]

Icon Pistons IC687-030 Fits BB Chrysler 383 Dome 4.5cc Bore 4.280

 

[Jerry Hall]

The 67 383 that I recently built is still standard bore, and the flat top stock pistons are 16 thousandths in the hole. I went with, I believe 020 steel shim head gaskets on the stock 516 closed chamber heads with the 1.60 exhaust valves changed to 1.74 with a little port work. The cam I chose is just under. 500 lift so no geometry changes needed.

 

[1 Wild R/T]

The 67 383 that I recently built is still standard bore, and the flat top stock pistons are 16 thousandths in the hole. I went with, I believe 020 steel shim head gaskets on the stock 516 closed chamber heads with the 1.60 exhaust valves changed to 1.74 with a little port work. The cam I chose is just under. 500 lift so no geometry changes needed. View attachment 1792891

Should make for a strong running 383.. Unfortunately steel shim gaskets are kinda hard on aluminum heads...