compression of a stock 1968,383????,

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Jims71duster

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I'm just looking for the rough numbers on a 68 383,, Its bone stock,, its got 906 heads, has not run since 1974 except for when I tryed it out to buy it. I know I have to rip it apart to re gasket and seal it but I was thinking about doing a little bit of internal work while it was apart but I don't want to go above 10:1. so if these are already a high compression engine then I wont do anything except bolt on's. Thx in advance
 
Jims71duster said:
I'm just looking for the rough numbers on a 68 383,, Its bone stock,, its got 906 heads, has not run since 1974 except for when I tryed it out to buy it. I know I have to rip it apart to re gasket and seal it but I was thinking about doing a little bit of internal work while it was apart but I don't want to go above 10:1. so if these are already a high compression engine then I wont do anything except bolt on's. Thx in advance
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There should be no problems at 10-1 which is what I'm running on my 70-383 with pretty agressive internals on pump premium but I personally wouldn't go any higher.

Terry
 
I think what he was asking is the compression of a stock motor. If it was a 2bbl. itis 9.2-1 if it was a 4bbl. it is 10.0-1.
 
1970duster440 said:
I think what he was asking is the compression of a stock motor. If it was a 2bbl. itis 9.2-1 if it was a 4bbl. it is 10.0-1.
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yup,,, thats the number I needed,Its is a 4 barrel ,,so if I'm right then thats as high as person wants to go for a street machine. Thanks for the help too terry {nice car also}
 
Measure how far the pistons are in the hole. A 10:1 factory engine usually is actually closer to 9:1. With the large combustion chambers on the chrysler big block heads its hard to get a true 10:1 in a 383 without pop up pistons.
 
If it`s the Magnum (old school ) version it would actually have a possitive deck height , around + .010 " . Watch the valve clearance when sellecting a cam. Get a set of 67' closed chamber heads with Felpro .043" head gaskets to get the comp way up . This however is not easy to live with on the street. (premium + booster all the time )
Have Fun !
Chryco 557 :wink:
 
dusterdon said:
Measure how far the pistons are in the hole. A 10:1 factory engine usually is actually closer to 9:1. With the large combustion chambers on the chrysler big block heads its hard to get a true 10:1 in a 383 without pop up pistons.
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Yes, the 340s were like that too. Rated at 10.5:1 but more like 9.5:1 actual. The factory compression ratings were not accurate. Thickness of head gaskets used can also make compression higher or lower.
 
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