compression: stock vs. rebuild

[HeavyFuel]

I took my 440 mag to the engine shop for a stock rebuild, and the pistons (Federal Mogul) that the guy used have a rating of 9.4 to 1.  I looked up the stock compression ratio for my engine, and it was 10.1 to 1.  Should I be pissed, or is this normal, or am I missing something?  Should help with the pump gas thing, but I kinda wanted it to be stock rebuild.  The engine was bored the typical .030 over, and I don't know if he decked the block or not, I hope he did.   

[golden73]

Did he mill the heads at all? If so, that would bump up the compression. Also, what is the head gasket thickness used?

[8WHEELER]

I would not go higher than 9.5 for a street car, and less will not hurt you unless you are
going to take it to the track or street race. If that is the case you can swap on a set of
closed chamber heads 915's are good and bump up your compression over a 906 head.

Dan

[golden73]

From what I have researched 10:1 with iron heads is too much for today's pump gas.
Aluminum allows a higher compression but I dont know how high? (anyone?)
9.4 to 1   sounds about right with iron.

With aluminum you can get to about 10.4-10.5 max on 93 octane

[HeavyFuel]

Thanks, guys. 

Sounds like my builder did the right thing when I told him it was going to be a driver.

Golden73, I don't think that he did anything special to the heads besides reworking the valves, and I'm sure he used whatever seal thickness a factory rebuild would call for.  Not much help there.

Dan, no strip or street racing for me, just hopefully lots of miles during good weather.

[is_it_EVER_done?]

Stock compression ratings were never what they were advertised to be (all makes, not just Mopar). Out of interest, I CC'd a cylinder and combustion chamber on a virgin 69 440 that I disassembled a couple of years ago, and it came out at 9.5:1

[Chryco Psycho]

I agree the factory compression was about the same as delivered  ,
you have the 2355 6 pack piston & open chamber heads the block can be milled  to Zero deck the pistons & use the steel shim gaskets instead of the thick composition one to bump the compression up to 9.7 approx which is lots with todays fuel