Technical -22 cc hemi pistons

I’m getting my 392 overboard .030 and deciding on pistons, should I use -22 cc pistons for naturally aspirated application on a stout street engine or other recommendations , I want around 10 to 1 compression on it with stock rods and crank ,heads will be stock also with stock gaskets , I’m a little confused on the math

 

CC your combustion chamber (the head) and let the piston maker do the math, tell him the CC's, what gasket and what you want for final compression ratio. Give him information and he'll do the rest.

 

As noted, you need to CC your heads - to know the chamber size - then you add a little bit for the gasket thickness (about 10ccs for your bore).

Here is info from Ross on their 22 cc domed pistons:

Ross dome top pistons for the 392 Chrysler Hemi: Compression ratio is 9.5-1 with a 107cc cylinder head chamber and 10.5-1 with a 97cc chamber.

 

Pretty sure you don't need that minus sign.

Even my Hemi blower pistons have a dome, just a small one, and I am at 8.5:1.

-22cc would be a dished piston.

 

Gimpy's exactly right - the 22cc is for the dome - as clearly noted in the Ross specs. It is not a 22cc dish.

 

I think the confusion is the CR calculators. They state (summits anyways) - for dome and + for dished.

 

That’s the way I understood it - is for domed and + is for dished am I wrong ? My 1957 3ne57 was rated at 375 hp factory from what I’ve read with 9.5 compression and they went to 10,5 in 1958 I’d like to come in at around 10.0 after I’m done

 

That is because you're reducing total CCs with a dome . . . and increasing total CCs with a dish . . . kind of b***-akwards from the piston manufacturers.

 

Once you set up a simple math problem
Say you’ve got a 100cc combustion chamber
you want to increase compression ratio with domed pistons and other math tells you you want 85 cc combustion chamber
100 -15 = 85 so that’s a -15 domed piston.
Or say it’s a 55 head and you want 85 cc
55 +30= 85 or a +30 dished piston.

 

10.5:1 works just fine with pump gas on a Hemi.

They can handle a little more compression that a wedge combustion chamber due to the namesake shape.

If you are having pistons made, just fill out the form. It will have a section for desired compression ratio.

Ross makes all of my Hemi pistons. They are absolutely flawless.

 

I understand why, but I think that is what confuses people who use the calculator.

 

Robert, before you order pistons have your machinist check the block to insure that the decks are parallel to the crank. If they are off a bit, not uncommon, then fix that before measuring deck height.

 

Good advice from 73RR - any align-boring and deck work needs to be done before measuring the compression height for ordering pistons. I never ***ume that the stock specifications are correct - always better to precisely measure and if you need to "move the pin a bit" to get the piston where it should be, then inform the supplier - Ross is usually happy to do it for a nominal fee.