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Discussion Starter · #1 ·
Refreshing my 350hp 327 short block. Pistons are forged L2166N. Looks like sealed power still makes their own version.

My question is where do I measure deck height? Off the machined outer area or off the inner area thats flat and not domed? Also, does anyone know what cc dome they are? I've been looking and haven't found anything.

Pic is before disassembly.

 

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Discussion Starter · #6 ·
Now that I have the dome number, where do I measure for deck clearance for the compression ratio calculation? I'm thinking it should be from the inner, highest flat area where STD is stamped, not the machined area around the circumfrence?
 

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Now that I have the dome number, where do I measure for deck clearance for the compression ratio calculation? I'm thinking it should be from the inner, highest flat area where STD is stamped, not the machined area around the circumfrence?
Correct.
If you want to get picky, you can also figure out the small lost amount from where they machined the rim around the top of the piston.
 

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Discussion Starter · #8 ·
Correct.
If you want to get picky, you can also figure out the small lost amount from where they machined the rim around the top of the piston.
Thanks, yeah not getting too fussy with this engine just want to get it running good again. Want to make sure I have enough compression so it runs good but not too much. I know the quench won't be great, but I'll live with it. Using the standard blue fel pro head gaskets from the kit with this one. I thought about using some steel shim gaskets but not sure how good the deck surface needs to be so they seal good. The heads were resurfaced. 76cc heads, 5.3cc dome, pistons .025 in the hole, .040 head gasket thickness comes out to basically 9:1. Using a Lunati Voodoo 702 cam with 219 int./227 exh duration @ .050. If I ran the steel shim gaskets, my quench would be a lot better at .043 but I'm worried that the 9.4:1 compression ratio might be a bit much for regular pump gas.

Oh yeah, and I would calculate my dynamic compression ratio but my cam came with a BLANK cam card. I'm going to need to call Lunati in the morning and hopefully they'll email me one. Their website has gone the way of all websites lately and is more slanted towards selling product than having useful information and they don't even have a way to look up cam cards anymore like they used to.
 

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There is a .028" thick composite gasket available from GM Performance, and a .026" from the aftermarket.

The version I use is the Mahle/Clevite Original/Victor-Rienz #5746.
Mahle Original, Head Gasket, Chev SB, 4.100" Bore, .026" Compressed, Each - Competition Products

Compression calculator I ised at Wallace Racing says your at 8.9:1 with your given dimensions and assuming 4.166" gasket bore since you posted "standard blue felpro".
With the Mahle gasket, it shows 9.22:1, with a not terrible quench of .051"
With .015" shim, it shows 9.47:1, with a great .040" quench.

Compression Ratio Calculator - Wallace Racing
 

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Discussion Starter · #10 ·
@ericnova72 The million dollar question is will the reduced sensitivity of .040" or .051" quench offset the increased compression ratio? This is going into a car that will be driven quite a bit but not a ton so it won't kill me to run premium in it but was trying to avoid it. I'm thinking it's probably a crap shoot.
 
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