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Old Sep 19, 2004 | 05:53 PM
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Question compression - what should it be?
Hi All,
I have an 87 F150 with 302, remanufactured short block from Ford with about 90k on the short block. 290k on the rest. I checked the compression of all cylinders today, lowest was 170psi, highest was 180psi. Problem is I don't know what the compression should be. Will the remanufactured block have a different spec than a stock engine?

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Brian
 
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Old Sep 19, 2004 | 08:56 PM
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I'm not sure what the spec is, but 170 -180 sounds good to me.
 
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Old Sep 19, 2004 | 09:49 PM
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As long as they are all within 25% of each other they are fine. That is about normal.
 
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Old Sep 20, 2004 | 04:46 PM
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Thanks for the replies, they both sound encouraging.

Brian
 
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Old Sep 20, 2004 | 07:23 PM
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I just installed my rebuilt shortblock and I'm only getting around 135 psi. Could my 351 cam cause compression loss? Maybe I need a valve job or something.
 
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Old Sep 20, 2004 | 07:43 PM
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can you determine CR with a compression check?
 
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Old Sep 20, 2004 | 09:02 PM
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If the engine has been bored the compression will be a bit higher than stock, same also if the pistons have a higher deck height.
 
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Old Sep 20, 2004 | 09:24 PM
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My 302 is bored .040 over and still only 135 psi?
 
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Old Sep 21, 2004 | 08:53 AM
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If the cam has valve overlap it can cause lower compression readings too.
 
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Old Sep 21, 2004 | 03:31 PM
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The 351 cam doesn't have more overlap than the 302 cam does it? In that case I'll go back to the stock cam.
 
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