383 PISTON HEIGHT

[BSB67]

I rebuilt a couple that I had back in the 70's and the parts book gave you a choice of positive or zero deck height for pistons. I actually went with the zero because the trick back then was to run 67 440 heads to have the closed chamber.

As long ago as 1978, you could not buy a 1.932" compression height replacement piston for a 383. You bought the 11.5:1 domed piston and milled most of the dome off to get a 10 or 10.5 CR

 

[Garys1969RR]

Oh wow! Never thought about that! I have always used the steel shim gasket . Started in the 70s. You know I have a 1969 383, from a Polara, buried in the motor pile at my son's house. I'll take it out next year and see what it's got for Pistons.

 

[chtampa]

I think the positive piston was a part of what made a Commando or Magnum motor. The change to open chamber heads started in 68, add the taller pistons, flowing exhaust manifolds and cam. Then you had that ultra fast unsurpassed 335 hp that is still the scourge of the street!

 

[PurpleBeeper]

All this stuff is interesting & all sounds correct..... I think to be sure, you'd have to measure your piston height vs. deck. I never knew that the idea of pistons sticking up out of the block for '68/'69 HP 383's was vs. the "blueprint spec" (but it sure sounds true). I never ran/rebuilt a '68/'69 HP 383, so I have no first-hand experience.

 

[miller]

Have to admit, every Chrysler engine I've been into, were HP types. Don't know on non-HP, but wonder if they used different rods that were shorter? I've always used YL rods, both 383s, and the first 440.
Any rate, used KB (237) pistons on the 440, supposed to be same dimensions as stock HP. Both decks, and heads cut .005", and wound up less than .002" in the holes. Used a .028" shim, to keep near stock CL.

 

[mopar 3 B]

Built the 68 383 in 1980.The Fel-Pro .040 gasket was something new and allowed the use of 915 heads.

 

[w.Hudson]

In the late 70's, 78 or 79, we built a 383 that performed better than any other 383 in stock form that I have been associated with.
Because the correct piston was not available we used a stock bore stock compression piston for a low performance 440. Bored a 1968 block to fit these pistons and it had a zero deck height. Used 906 heads and a stock 440 HP 375 horsepower cam and exhaust manifolds.
This motor stills runs today.

 

[Garys1969RR]

How much did you need to bore it? About .065" ? That's a lot to bore a 383 block. Sounds like it worked out well.

 

[w.Hudson]

Yes it was less that .070 over bore. We set the piston to cylinder clearance at .0045 and put some easy street miles on before it made any wide open runs.
I wish I had a dollar for every person that told me that it wouldn't work LOL

 

[Cartel]

just reading this thread. can I used L2315 pistons in a 66 383 and 516 heads?

 

[BSB67]

just reading this thread. can I used L2315 pistons in a 66 383 and 516 heads?

Yes.

 

[Cartel]

Yes.

ok thanks. I see they have 1.920 comp h
they only list them for 68 up not 66.
is there something about that I should look into?

thank you for the fast reply!

 

[BSB67]

ok thanks. I see they have 1.920 comp h
they only list them for 68 up not 66.
is there something about that I should look into?

thank you for the fast reply!

Blocks are generally the same within production tolerances. That piston will be about 0.015 to 0.020” below the deck on an uncut block. Head gasket choice accordingly.

If you’re adding a medium performance cam, check piston to valve clearance. A big cam probably won’t clear.

 

[Kern Dog]

I've heard some engines were as much as .100" in the hole ....

My '70 383 2 barrel pistons were .076 down.

If you measured all the unrestored 383's out there, they are probably all over the place. Mopar certainly didn't have time to blueprint deck heights. My 68 (disassembled in 1980) was 30 in the hole.

Mine was rated at 8.8 to 1? It calculated at 8.12. Using a .039 Fel Pro head gasket would have dropped it to 7.85.

 

[mopar 3 B]

Just remember 516 heads are closed chamber. 906 heads 68 and up where open.
Don't forget to check piston to head clearance on the 516 head. They may require thicker head gaskets to get the right clearance.