390 Compression Test PSI
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Joined: Feb 2011
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From: California
390 Compression Test PSI
I was talking to my buddy the other day and he had some "Mechanic" come and check out his 72 F-150 Custom with a 390. The "Mechanic" did a compression test and told him that it was at 200 psi and that is too high. I was trying to find some info about what psi you should get when doing the test and it looks like 135-150 (+or- 10% for all the cylinders) is normal. I went to take a closer look at his truck and I think it has cobra heads on it, I am basis this on the 200psi compression test number and the very nice looking valve covers that say cobra on them. I was just wondering if this sounds correct.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com
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Senior User
Joined: Sep 2010
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well just bc the valve covers say cobra on them, dont mean they really are. i have cobra valve covers on my 302 haha, just bc they look really cool. and another thing, i would double check on that comprassion test, that sounds really high, even if u did have the cobra heads. what are the casting numbers on the heads?
Fleet Mechanic
Joined: Dec 2006
Posts: 1,338
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From: UPSTATE NY
dont know about what it should exactly be. mine on all cylinders was around 120, with cylinder 7 at like 105
i believe what is key is that all the cylinders are somewhat uniform and even if the engine is worn, what you are looking for is them to be within a certain amount of each other and evenly worn.
but then you should also have a leakdown test done.
i believe what is key is that all the cylinders are somewhat uniform and even if the engine is worn, what you are looking for is them to be within a certain amount of each other and evenly worn.
but then you should also have a leakdown test done.
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NEMOTORCARS
6.7L Power Stroke Diesel
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Nov 6, 2013 07:08 AM
1967, 1972, 352, 390, check, compression, compressioncheck, compresson, engine, ford, numbers, psi, results, test, wayt
