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Discussion Topic:
Compression
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Fhower |
12-08-2018 @ 12:15 PM
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Member
Posts: 32
Joined: Dec 2016
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I have a 1941 Convertible with a 59A Flathead. It runs smooth and no smoke, but has low compression, around 60lbs. My altitude is around 5,000 so normal should be around 90lbs. I have thought a short block from H&H might be in order, and would essentially have a new engine, but it is pricey at $3,500. Any thoughts or suggestions would be greatly appreciated!
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ford38v8 |
12-08-2018 @ 1:36 PM
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Senior
Posts: 2774
Joined: Oct 2009
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Don't fix it if it ain't broke.
Alan
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carcrazy |
12-08-2018 @ 1:45 PM
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Senior
Posts: 1680
Joined: Oct 2009
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If it runs smoothly and all of the cylinders have compression pressures that are within 10 PSI of each other, I would just drive it and enjoy it. I never want to open up a good running engine just to make it "perfect".
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MG |
12-08-2018 @ 2:01 PM
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Senior
Posts: 1262
Joined: Nov 2009
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What procedure did you use to check the compression?....
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cliftford |
12-08-2018 @ 2:54 PM
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Senior
Posts: 845
Joined: Jan 2014
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Was the battery strong and did you hold the throttle open when cranking it? Is your compression guage accurate?
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Fhower |
12-09-2018 @ 8:02 AM
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Member
Posts: 32
Joined: Dec 2016
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I keep the battery (Optima) on a charger and it appears to be strong. I did not have the throttle open however. I will retest it, I assume this is to make sure the is adequate air getting to the cylinders. The procedure was to take a compression tester on each cylinder and crank it with a remote switch. I did check the compression tester against my air compressor and it seem pretty accurate (set the regulator to 60lbs and the compression tester, with adapter, read same.) I really appreciate the thoughts.
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cliftford |
12-09-2018 @ 8:45 AM
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Senior
Posts: 845
Joined: Jan 2014
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One more thought: Did you crank the engine over at least 3 revolutions for each cylinder?
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TomO |
12-09-2018 @ 8:48 AM
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Senior
Posts: 7263
Joined: Oct 2009
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I would not replace the engine when low compression is the only problem. The engine should be at operating temperature (drive it for at least30 minutes, maybe longer in the cold weather), the throttle should be wide open and the battery at full charge before taking a compression reading. If your readings are consistent across all 8 cylinders, the engine runs smoothly and seems to have adequate power, I would leave it alone. If it is lacking power, I would talk to someone in the High Country Regional Group about timing and carburetion for high altitudes.
Tom
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Ev |
12-09-2018 @ 7:28 PM
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Member
Posts: 1
Joined: Dec 2018
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Hello: 1. An unscientific question to ask. Did you check your 59A block compression at 5000 (approximately mile high) feet? If so, do you have the opportunity to check your compression at near sea level to see if your compression increases or remains as 60 pounds at your advertised altitude? 2. Would you consider judicially shaving your heads or using a thin copper gasket to increase your compression at your mile high geographic location? As usual, shaving a head or using a thinner head gasket on a flattie may run the risk of valve interference into the head or reduction of airflow.
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CharlieStephens |
12-09-2018 @ 7:46 PM
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Senior
Posts: 894
Joined: Oct 2009
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I would like to send you an email or PM but both of them are disabled. It might be valuable to you if you changed that. A general location might also prove valuable at some point. In the meantime, how about sending me an email at the address shown in my profile? Charlie Stephens
This message was edited by CharlieStephens on 12-9-18 @ 7:48 PM
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