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Old 08-19-2012, 08:49 AM   #1
DR
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Default 1930 Model A engine compression

Does anyone have the range for compression on the for the engine. My compression test was 50, 60, 0,0, I have a blown head gasket between the 3rd and 4th piston. Just wondering if anyone could provide some normal readings. There was water coming out the oil pan when I drained it. Any suggestions on what else I should be doing in terms of getting it back into top performance?

Thanks
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Old 08-19-2012, 08:56 AM   #2
lindy williams
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Default Re: 1930 Model A engine compression

65 lbs new engine with stock head. 50-60 lbs, good used engine. Below 45 lbs, definitely bad valves / and or rings.
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Old 08-19-2012, 08:57 AM   #3
lindy williams
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Default Re: 1930 Model A engine compression

65 lbs, new engine with stock compression. 50-60 lbs, good used engine. Below 45 lbs. definitely bad valves/ and or rings.
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Old 08-19-2012, 09:30 AM   #4
Al 29Tudor
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Default Re: 1930 Model A engine compression

I also had a blown head gasket a couple of months ago and even had water in the valve chamber and out the exhaust pipe. It might be a good idea to open up the valve chamber and dry it out.
Good luck.
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Old 08-19-2012, 09:51 AM   #5
Tom Wesenberg
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Default Re: 1930 Model A engine compression

I always use 50% antifreeze, which can destray babbit and inserts if it gets into the oil, so if that what you also use be sure to get it all out of the pan and dipper tray.

Look for evidence of how the water got into the pan. You should see marks in the gasket where water has travelled, or maybe a crack in the head or block.
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Old 08-19-2012, 03:15 PM   #6
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Default Re: 1930 Model A engine compression

Quote:
Originally Posted by lindy williams View Post
65 lbs new engine with stock head. 50-60 lbs, good used engine. Below 45 lbs, definitely bad valves / and or rings.

Is that checking with a differential pressure tester or the 'ol turn-the-engine-over-with-the-starter method?
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Old 08-19-2012, 10:17 PM   #7
DR
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Default Re: 1930 Model A engine compression

Thank you for all the advice. I checked it with a snapon pressure gauge and turned the engine over with with the starter. Sounds like I am in for a treat, and some learning about engines more indepthly. But this is good for me, to explore things like this anyway. I appreciate the advice.

Regards,
Dan
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Old 08-20-2012, 12:47 AM   #8
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Default Re: 1930 Model A engine compression

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Originally Posted by socalplanedoc View Post
Is that checking with a differential pressure tester ... ?
How many of us that are not an A&P have one of these, or even know what one is?
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Old 08-20-2012, 06:45 AM   #9
socalplanedoc
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Default Re: 1930 Model A engine compression

ya, I know... occupational hazard I guess. But when I see compression numbers that low it makes me wonder. Even my old international hit-miss will make numbers higher if you crank it long enough. I see so much variance in technique using the "run it with the starter" method that when I don't feel comfortable using it to judge the health of an engine that i havent known since it was new.
I manage the maintenance on a dozen planes - doing a Skylane with a Continental O-470 right now (6 cyl, opposed, 471 Cu. in. 230 hp). Diff test, borescope, oil analysis, examing the contents of the oil filter, inspecting all 12 spark plugs, fuel flow/cyl temp/exhaust gas temp data stored and downloaded... all that really spoils a mechanic and makes it pretty easy to diagnose engines
I'm still a rookie when it comes to Model As though... the temptation to put a bunch of probes on it is strong... It's hard to resist the dark side
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