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Re: Stock 1972 318 compression height?
[Re: 6o4o]
#354440
06/22/09 11:37 AM
06/22/09 11:37 AM
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Joined: Mar 2005
Posts: 11,269 Slantytown
DUFFMAN
Ask And Ye Shall Receive
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Ask And Ye Shall Receive
Joined: Mar 2005
Posts: 11,269
Slantytown
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My brother just had the heads off his stock, 53k original mile, 1972 318 about a month ago. The below deck height of his pistons measured at 0.070", but I've read that a stock 318 can be as far as 0.090" in the hole.
Assuming 0.070" in the hole, if you just go to a 0.028" MP head gasket you would get 8.97:1 compression. For ever 1cc you remove from the chamber you will gain about 0.1 in compression ratio. What that translates into for how much you have to mill off your heads I don't know exactly, but it should be about 0.005-0.006". Thus to gain another half point in compression ratio you are going to need to remove about 0.030" from the heads.
No longer taking $h!t from anyone!
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Re: Stock 1972 318 compression height?
[Re: stumpy]
#354442
06/22/09 12:27 PM
06/22/09 12:27 PM
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Joined: Mar 2005
Posts: 11,269 Slantytown
DUFFMAN
Ask And Ye Shall Receive
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Ask And Ye Shall Receive
Joined: Mar 2005
Posts: 11,269
Slantytown
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Yes you need to remove 0.0095" of the intake surface for every 0.010" you remove from the deck. So for 0.030" off the deck remove 0.0285" from the intake surface.
You will also need shorter push rods. The stock push rod length is about 7.500". (it varies a little) Here's the formula to figure out what length push rod you need;
Push Rod Length = 7.500 - Delta/cos(14) Delta = amount milled + difference between old and new head gasket crush
This is assuming you don't change your cam and/or lifters, then you need to take the cam base circle and lifter length into account. If you are changing cam and lifters I recommend you get an adjustable push rod and a cheap 8" calipers from HF to determine what your push rod length needs to be.
No longer taking $h!t from anyone!
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Re: Stock 1972 318 compression height?
[Re: DUFFMAN]
#354443
06/22/09 04:02 PM
06/22/09 04:02 PM
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Joined: Jan 2003
Posts: 16,123 Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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silvolite replacements are 1.741 CH, sealed power replacements are 1.72", I'd guess it's somewhere around there....
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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