360 Deck Height

[it's all dodge]

I believe my late '75 360 should be a 9.599 deck height, right? Just wondering how many on here have measured a stock virgin block, and what deck height did you actually have?

[345Dart]

9.584 here

[it's all dodge]

So wouldn't a piston with an adverticed compression distance of 1.637 be .05 in the hole .050? if I really had a 9.599 deck? Half the stroke,+ rod length, + compression distance, deck height minus the compression height .050? I got near .070 in the hole, whats up with this?????

[345Dart]

Originally Posted by it's all dodge

So wouldn't a piston with an adverticed compression distance of 1.637 be .05 in the hole .050? if I really had a 9.599 deck? Half the stroke,+ rod length, + compression distance, deck height minus the compression height .050? I got near .070 in the hole, whats up with this?????

1.79+6.123+1.637+.050= 9.600" Maybe you have a tall block of 9.620. Its possible - just like mine was supposed to be 9.600 and it was 9.584 or .016 less than advertised stock.

[it's all dodge]

It's cause the compression height was not what Summit said (mis information on their part) the real height for the SEALED POWER 405 CP is 1.576, called the tech guy at SEALED POWER. Not their fault, SUMMIT RACING needs to get it together! So my machine shop DID do as they said (milled about .040 off the block) Now I am stuck with some .111 in the hole pistons, well, before we decked it, if I hadn't decked anything, or not milled the heads with stock valves, it woulda been in the 7s for compression.YEEEE HAAAWWWW!

[86 MOPAR]

For what it's worth, when I took my 360 apart I measured the deck clearance and it was on average .110" in the hole with a dished piston. Some quick measurements of the dish, figuring on a standard Felpro Gasket, and with let's say a 65cc head since I don't know what mine actually are, would make it a 7.78:1 compression ratio.

I have not measured the true deck height yet, but I know this engine has never been apart before. The engine is a flat tappet carbureted 360 from a 1/2 ton 1986 PU. Hope this helps, CJ

[Jacksdad]

Originally Posted by it's all dodge

It's cause the compression height was not what Summit said (mis information on their part) the real height for the SEALED POWER 405 CP is 1.576, called the tech guy at SEALED POWER. Not their fault, SUMMIT RACING needs to get it together! So my machine shop DID do as they said (milled about .040 off the block) Now I am stuck with some .111 in the hole pistons, well, before we decked it, if I hadn't decked anything, or not milled the heads with stock valves, it woulda been in the 7s for compression.YEEEE HAAAWWWW!

Been there myself. The 405s I got in a kit from Summit were supposed to give me 9:1 if memory serves (it was a while ago), but when I measured everything and cc'd the heads (which had already been milled) I was looking at closer to 8:1 - about the same as the 7.8:1 stockers I was replacing. On top of that, when I had the block decked I found the passenger side needed an extra 10 thou machined off to give me matching compression heights. Live and learn...