440 Comp. ratio and piston height

[mike1965]

The pistons I have are the 2350p sealed power , now with the 77-78 block what would I need to do to get 10.5 - 11.0 comp. what head cc and what deck height.

How much taller are the 2350p pistons compared to the 1977-78 stock pistons

 

[Garys1969RR]

First thing we need to know is the C/H of that piston. Do you know what it is?

 

[mike1965]

First thing we need to know is the C/H of that piston. Do you know what it is?

Compression Distance (in):
2.061 in.

 

[Garys1969RR]

OK with a C/H of 2.061", your piston will be .021" below deck. Using the United Engine and Machine C/R calculator, and these specs: .020 gasket thickness, 4.350 cyl bore (.030 O Size) 84cc head volume such as the Eddy Performer RPM has, you get a C/R of 10.7 to 1.

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This assumes a gasket diameter of 4.40". This will also get you a squish/quench area of .041" which is just right for that engine.

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I was tryting to find that piston on the Summitt web site, but couldn't locate it. Only found 350np30 Where did you get yours?

 

[mike1965]

OK with a C/H of 2.061", your piston will be .021" below deck. Using the United Engine and Machine C/R calculator, and these specs: .020 gasket thickness, 4.350 cyl bore (.030 O Size) 84cc head volume such as the Eddy Performer RPM has, you get a C/R of 10.7 to 1.

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This assumes a gasket diameter of 4.40". This will also get you a squish/quench area of .041" which is just right for that engine.

Thanks Gary for that info that was what I was looking for.

Now can you please tell me the stock piston C/H on a 1977-78 motor

 

[bigmanjbmopar]

I cc'ed mine -24cc to get 9.6:1 just throwing it out there.

 

[Garys1969RR]

I had a 77-440 that I took apart, and the pistons were way down below the deck. I'm thinking .120 to .140 down. All deck heights on the 440 have the same factory spec of 10.725" from the crankshaft centerline to the deck surface. But they do vary. Don't know the C/H on a 1977-440 piston.

 

[Meep-Meep]

In my experience the late model 440's have a huge bore chamfer that is worth a few cc's by itself. As an example my 77 440 has the KB 237's that are about .015" in the hole, steel shim gaskets and 915 heads. All that comes out to 10.1:1. If this was on an early block I bet it would be close to 10.5:1