Re: Help me pick the right pistons. 78 440
[Re: cougar_cat_25]
#2639204
03/31/19 03:05 PM
03/31/19 03:05 PM
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Joined: Jul 2004
Posts: 3,813 Arlington, Texas
bobby66
master
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master
Joined: Jul 2004
Posts: 3,813
Arlington, Texas
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Went to freshen up my 1978 440 before slapping on the new trick flow heads and found a cracked ring land. Engine builder has retired and pistons don't have part numbers stamped, so might as well do a set. Current set up with stock heads and cast crank was supposed to have a 9.5 CR (bore:4.350, stroke: 3.75, chamber volume: 92 cc, deck height: 0.10, comp height: 1.988, weight: 860 g, weight with pin: 1122 g). Biggest change will be the 78 cc chamber on the TF heads. My understanding is the aluminum heads would handle the higher comp ratio if I stuck to the same size piston. So hypereutectic or forged? How close to weight do I have to get? For example I found a forged set that weighs 1072 grams with pin. Thanks guys The Sealed Power 2355's would be a good place to start. Small valve reliefs, though....
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Re: Help me pick the right pistons. 78 440
[Re: cougar_cat_25]
#2639256
03/31/19 06:09 PM
03/31/19 06:09 PM
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Joined: Jun 2008
Posts: 3,916 usa
lewtot184
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master
Joined: Jun 2008
Posts: 3,916
usa
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You're right. I ran those number through a CR calculator and I don't know how he thought it came to 9.5! Valve relief would be a good idea, and 10.3 would be a good number to shoot for. you might get a 10.3 number with Icon 836's and take some weight off.
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Re: Help me pick the right pistons. 78 440
[Re: cougar_cat_25]
#2640087
04/02/19 09:18 AM
04/02/19 09:18 AM
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Joined: May 2011
Posts: 4,489 northern,Ohio,USA
Clanton
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master
Joined: May 2011
Posts: 4,489
northern,Ohio,USA
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Lighter pistons are better than heavier and I think I read that 10 grams +/- would work but all have to be equal weight.The crank should have a balance weight mark on it saying what weight.
Last edited by Clanton; 04/02/19 09:25 AM.
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