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Discussion Topic:
no compression
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runningon8 |
11-13-2016 @ 9:03 AM
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Member
Posts: 44
Joined: Oct 2016
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1936 engine rebuilt in 93 and approx 3500 miles since rebuild so obviously has sat a lot. Engine fires right up but has a slight miss. Changed plugs and noticed one was fouled when I replaced them. Ran a compression test and all cylinders are at 90 except the one with the fouled plug. If its a stuck ring couple mechanics told me to spray PB Blaster in the cylinder and let it set for a couple days then put oil in cylinder, spin with plug out, then plug in before firing engine. Could also have a stuck valve, broken push rod, rocker arm which now will require dismantling engine. Any ideas on other simple solutions before taking a wrench to her.
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alanwoodieman |
11-13-2016 @ 1:11 PM
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Senior
Posts: 868
Joined: Oct 2009
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more than lily a stuck valve, my advice is to put a mixture of 50% atf and 50% acetone in the cylinder and if at all possible blow a little up towards the valve. what happens is the oil drains from the cast iron guides and then the valve stems rust to the guide--what compression did the foulded cylinder have?
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flathead4rd |
11-13-2016 @ 4:44 PM
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New Member
Posts: 169
Joined: Oct 2009
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There are no push rods or rocker arms in a flathead engine. You most likely have a stuck lifter or valve. If you can't free it up with the given advice then your easiest next step is to pull the intake manifold and check the valve train. No need to pull heads at this point.
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cliftford |
11-13-2016 @ 5:37 PM
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Senior
Posts: 845
Joined: Jan 2014
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My opinion: low compression and a fouled plug on one cylinder sounds more like broken or stuck rings than a stuck valve. Do another comp. test, putting oil in the weak cylinder and see if the comp. comes up. If so, it would indicate rings. Soaking it may or may not help the problem.
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runningon8 |
11-13-2016 @ 7:43 PM
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Member
Posts: 44
Joined: Oct 2016
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No compression at all.
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runningon8 |
11-13-2016 @ 7:52 PM
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Member
Posts: 44
Joined: Oct 2016
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No compression at all on the cylinder. I did put some oil in there and the compresssion came up ever so slightly. I will try the mixture recommended and see if that does the trick, if not will be pulling intake. Thanks for the advice.
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Drbrown |
11-13-2016 @ 10:29 PM
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Senior
Posts: 571
Joined: Nov 2013
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Picking-up on cliftford's post and your thought about a broken rod, and although a rare occurrence, no or near zero compression MAY indicate a damaged piston. Loading the cylinder with oil should have done more than tickle the compression reading above zero. No coolant in the crankcase would indicate the absence of a cylinder wall defect. A vacuum meter reading might indicate some interesting info (i.e. they can indicate defective valves)
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GK1918 |
11-14-2016 @ 12:41 AM
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New Member
Posts: 128
Joined: Aug 2016
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I would get that piston up both valves closed and apply shop air. Then you will hear leaking air coming from carb (leaking intake valve) tail pipe (leaking exhaust valve) or oil filler pipe (ring / piston) realated..........
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