| Flatbob | -- 11-02-2009 @ 8:01 AM |
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My '36 after a rebuild that I did has low compression 60-90lbs. Have driven car 35 miles, no smoke and idles nicely. I think I may have adjusted the valves improperly during assembly. The engine is in the car, no timing marks on crank pulley, heads & pan on; so how do I find TDC? I know I want piston all the way up on power stroke and both valves closed.
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| supereal | -- 11-02-2009 @ 9:23 AM |
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Pull the plugs, and put your finger over the plug hole as you turn the crank pulley. You will feel pressure when the piston comes up on the compression stroke. If your engine idles properly, makes no smoke, and you don't hear any valve clatter, I'd just drive it and have fun. If you find one or more cylinders a bit low on compression, squirt some oil into the cylinder and test again. If the compression doesn't rise, it could be a leaky valve. Flatheads before '49 have no timing marks on the crank pulley.
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| Flatbob | -- 11-02-2009 @ 12:24 PM |
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Super, I believe I can hear one lifter making noise but I have very little experience with a flathead so am not sure what I should hear, am guessing that's the cylinder showing 60lbs. I've put MMO in the tank & crankcase. I have 35 miles on the engine and so far has performed ok, suppose to take it 8 miles to the upholstery shop tomorrow for the top, probably "sweat bullets" all the way there and back. Thanks for the help.
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| supereal | -- 11-02-2009 @ 1:04 PM |
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Having one lifter make a clicking noise is about "par for the course" for most of us. If that is the cylinder that is low, it is doubtful the valve clearance is at fault, as a too tight clearance doesn't make noise, as does one that is too loose that taps. With that few miles on a rebuild, I'd drive it a while, as you may see some improvement as the rings seat. Often, not staggering the ring gaps can cause low compression, but it may be temporary. Have fun with your car. Don't overdo the MMO. We are seeing spark plug fouling when it is overdosed.
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| TomO | -- 11-03-2009 @ 7:45 AM |
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Use a screwdriver or a stethoscope to isolate the ticking. If it is coming from the cylinder with the low compression and oil in the cylinder does not raise the compression, remove the intake manifold and inspect the valve guide for that cylinder. You may have missed the groove for the horseshoe clip in the guide and the guide is just being held in place by friction. I have found it easier to determine if the clip is in the correct position if I take the valve removal tool and pull the guide down for a visual check. Tom
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| BERTHA | -- 12-04-2009 @ 7:06 AM |
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I use a whistle attached to a compression tester fitting. Screw into #1, crank over by hand when it stops toot'n it's TDC.
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| 51f1 | -- 12-04-2009 @ 12:11 PM |
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Sorry, but being a '51 truck owner, I always feel compelled to correct people when they say or imply that the 8BA/8RT engine was built between '49 and '53 ("Flatheads before '49 have no timing marks on the crank pulley"). Actually the 8BA/8RT engine was used in '48 model trucks. It was not used in cars until 1949. A correct statement would be: Flatheads before the 8BA/8RT engine in trucks in 1948 and in cars in 1949 have no timing marks on the crank pulley. The 8BA and 8RT engines are virtually the same engine. Richard This message was edited by 51f1 on 12-4-09 @ 12:13 PM
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