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502 with low compression

Old 10-07-2008, 07:56 AM
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Default 502 with low compression

I am looking to buy a 27 fountain and just had a compression test done on it. It’s a 502 mag with 166hrs on it. All the cylinders were around 150 except #5. It was 110. Any ideas on what the cause could be and how much it would be to fix. I know its hard to tell without pulling the motor apart. I am trying to figure out how much to drop my offer that I made him. Should I bail out on the deal?

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Rob
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Old 10-07-2008, 08:30 AM
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With low hours like that I would suspect valve issues due to a failed injector. I tulipped 3 valves on one of mine due to low flow from the injectors. You could have a leakdown test done, that should tell if it's valve issues for sure.
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Old 10-07-2008, 05:30 PM
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you can shoot some reg oil in the cyl and re-ck if it goes up then you have a piston/ring issue(doubtfull though) my bet is a valve..Rob
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Old 10-07-2008, 06:45 PM
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Get a leakdown test performed and it will tell you if it is valves or rings and then you can accurately make an offer based on that.
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Old 10-07-2008, 07:14 PM
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Default low compression

my27fountain was the same way when i bought it.it is a 94 502 mpi,mag.it had 395hrs when i bought and 6 was week,[guy let the riser gasket leak].i used that as a barging tool also.knocked off 600 bucks.with few hours on your motor,i would not suppect that issue,but the can leak from the inside out.maybe it got a back wash and hurt a valve.hope this helps
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Old 10-07-2008, 08:35 PM
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did it ever get hot?
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