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  #1  
Old 12-17-1999, 04:06 PM
mopar_nerd mopar_nerd is offline
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I need to know the size of the combustion chambers for these two heads. I know that the compression ratio is lower for the 340 from 1971 and up, but is it because of the heads or the pistons? Or both?

Thank You

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  #2  
Old 12-17-1999, 08:20 PM
Elwenil Elwenil is offline
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Ok, here is the info I have on 340 heads, I hope that it is accurate, but if not, I'm sure someone can correct it. Here goes:
68-71 Cast.# 2531894, 63cc
70T/A Cast.# 3418915, 65cc
72 Cast.# 3418915, 65cc
73 Cast.# 3671587, 65cc
ok, that one has me stumped. I dunno if my book is wrong or the T/A heads may have just had radically different machining on the same casting as the 72 heads. I'm not that familiar with T/A heads to be honest. Anyone else?
~Elwenil~ ~.\|/.~
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  #3  
Old 12-18-1999, 12:16 AM
340king 340king is offline
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I don't know about the "X" or "J" heads specifically, but I recently cc'd a set of 273 commando heads. They were 65 cc's. I thought they would go closer to 60 flat. With this in mind, I would be surprised if the open chambered heads were under 70 cc's.

The chamber on the T/A heads should be the same as the "X" or "J" heads. The only difference should be the intake pushrod location and the offset intake rocker.
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Old 12-18-1999, 10:15 PM
340dave 340dave is offline
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My x heads are 63 cc. The change in compression ration was in the shorter pistons. the 10.4-1 pistons stick out of the block at tdc, I think mine were out .014 or so. The lower compressi0on engines also had the cast crank.
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  #5  
Old 12-21-1999, 08:20 AM
Dave Dave is offline
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What ever you do you actually need to do the cc'ing of your heads. The book will tell you what it is supposed to be but it is typically WAY off in stock form. I just did a set of 015 cop heads from 1980 and the spec on them is supposed to be 68-72 cc. The machine shop told me these things measured out at 80cc!! Checkum.
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  #6  
Old 12-21-1999, 11:48 AM
DartGT66 DartGT66 is offline
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Every single head I have measured has been way over the factory ratings, but I haven't kept book about them. Latest measurement was stock '83 318 heads that were 68cc. The '68-71 heads I prepared for the engine had a 'deep' valve job done, and after I modified the chambers they were 73cc. These heads on a stock 318 short block would give about 7.5:1 CR, a little on the lower side. That is, if you have a blower.
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