Re: TRUE compression ratio for 1969 440
[Re: BSB67]
#2274024
03/22/17 12:09 AM
03/22/17 12:09 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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IIRC JohnRR priorly posted that a 68-69 piston has a 2.030"CH & is ~.050 in the hole (as we know block deck heights vary) but you might plug it all into united machines' calculator. You know the std bore and stroke & the gasket dimention is available along with a good guesstimate on the 906's CC's & I'm assuming the piston has reliefs (find that info too) then let your fingers do the walking. also see if there are differences in 6pak pistons (not my area).
live every 24 hour block of time like it's your last day on earth
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Re: TRUE compression ratio for 1969 440
[Re: fast414]
#2274089
03/22/17 03:54 AM
03/22/17 03:54 AM
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Joined: Aug 2003
Posts: 43,129 Bend,OR USA
Cab_Burge
I Win
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I Win
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Posts: 43,129
Bend,OR USA
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Iam to believe that a 1969 440 has a compression ratio of 10:1 to 10:5:1 ........how is that when the piston is down in the whole and the heads are open chamber ????......wouldn't the compression be like 9:2:1 ??
Not the four barrel magnum motors from the factory would be over 9.7to1, probably closer to 8.8 to 1 I've CC a lot of stock 906 heads that had 92.0+ CC per chamber and those stock magnum flat top pistons with no valve reliefs where down over -.030 in the hole No where close to NHRA blue print specs.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: TRUE compression ratio for 1969 440
[Re: fast414]
#2274216
03/22/17 01:32 PM
03/22/17 01:32 PM
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Joined: Jan 2003
Posts: 14,493 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
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So. Burlington, Vt.
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9.2-9.4 is about where the math comes out........ Depends on the actual deck clearance (block height) and chamber volume.
The added c/h of the 6bbl piston is offset by the 4 valve pockets, so there is no gain in compression with those pistons over the 2.030 c/h 4bbl piston.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: TRUE compression ratio for 1969 440
[Re: fast68plymouth]
#2274268
03/22/17 03:34 PM
03/22/17 03:34 PM
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Joined: Jan 2003
Posts: 25,757 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
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Posts: 25,757
Rio Linda, CA
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Stock '68-'69 Magnum with 90 cc heads, .050" deck and a .022" head gasket is around 9.4-1
The INTERNET, the MISinformation superhighway
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Re: TRUE compression ratio for 1969 440
[Re: fast414]
#2274285
03/22/17 03:55 PM
03/22/17 03:55 PM
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Joined: Jan 2003
Posts: 74,979 U.S.S.A.
JohnRR
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Iam to believe that a 1969 440 has a compression ratio of 10:1 to 10:5:1 ........how is that when the piston is down in the whole and the heads are open chamber ????......wouldn't the compression be like 9:2:1 ??
Factory advertised and ACTUAL compression ratio are not the same when it comes to Ma Mopar . they ran on pump gas in the day because the gas then is not the same as the swamp water being passed off a gasoline today ...
running up my post count some more .
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Re: TRUE compression ratio for 1969 440
[Re: fast414]
#2274518
03/22/17 10:43 PM
03/22/17 10:43 PM
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Joined: Jan 2003
Posts: 14,493 So. Burlington, Vt.
fast68plymouth
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I Live Here
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Posts: 14,493
So. Burlington, Vt.
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That's a fair question Russ.
You're probably correct in that "new" they were likely closer to 87-88cc.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: TRUE compression ratio for 1969 440
[Re: fast414]
#2274769
03/23/17 01:22 PM
03/23/17 01:22 PM
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Joined: Jan 2003
Posts: 74,979 U.S.S.A.
JohnRR
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I have checked more than one 906 that was never rebuilt, and never cut, and they were 90+ , valve recession ?
running up my post count some more .
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