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Compression values

2K views 3 replies 3 participants last post by  D Pope 
#1 ·
I'm starting to develop a parts list for my 460 build. I'm looking at the compression ratio calculator listed on Summit's website and I don't know the answer to some of the filtering options. Gasket thickness and deck height specifically. I keep reading about having the block 0 decked in several threads on here. What is the stock deck height, or is there a difference from one year to another? Also, what is the standard head gasket thickness? On previous rebuilds, I've just bought a Felpro gasket kit from O'reilly. I'm trying to figure out what combination of heads vs piston type I need to maintain a safe premium 91 octane pump gas compression ratio. I don't have immediate access to my motor, so I'm unable to get the engine numbers to tell what year block I have. I just know it's a 429, but I plan on going with a 460 crank.
 
#2 · (Edited)
Most 429/460 head gaskets are .038-.046. Felpro's standard gasket is .041. Most are have a 4.500 bore diameter.

Deck is the distance from the top of the piston to the top of the block/head gasket surface. Zero deck means they are the same height. Factory blocks ranged from 10.300 to 10.322 deck height (in theory), but this is of little consequence as you're going to deck the block to set the piston/deck height as desired, and stack height of pistons can vary from one manufacturer to another. Generally, 0 to -.005 deck is most desirable with commonly available head gaskets.


;)
 
#3 ·
Thank you for the reply. My knowledge of engine building has mainly been near stock replacement parts. Stock crank, heads, new pistons at whatever bore size needed, stock heads, etc. This is my first actual performance build where I want to pick and choose performance parts.

Reading your post, you figure the block will be decked to match whatever pistons you're running, so does stack height matter? Just assuming I'll have to bore it .030 over, and a 3.85 stock 460 crank, with 95cc Edelbrock heads, a .041 head gasket, and 11cc dish pistons the compression calculator comes up with 9.22-1. Would this be a safe ratio for 91 octane, mostly plains driving in Kansas with occasional towing of my car or pickup?

I also looked at 75cc heads and 33cc dish pistons with a 9.08-1 C/R. I haven't bought heads yet, but have settled on Edelbrock performer RPMs and just curious which combustion chamber/piston combo would be best for my application. Nothing radical, just a street cruiser with occasional towing duties. I realize cam selection is going to be another determining factor in overall performance of the vehicle, but I assume I need to get the piston and head combo figured out first to determine what cam is needed.
 
#4 ·
On a stock block the deck height will vary up to .040 or so from one cylinder to the other so decking the block makes them all the same as well as setting the quench distance.
 
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