| woodwagon47 | -- 10-27-2009 @ 3:56 PM |
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I have a 47 ford with an engine that was rebuilt about 6 years ago. I devoleped a poping noise and got worse. I ran a compression test on it and found 5 - 8 only have 20 lbs compresion. I has adjustable lifters. I checked the adjustment and the exhaust was a little tight. I reset it at 14 and still 20 lbs. I pulled the head off and everything looks OK. Should i do a valve job on it or what. This engine ran fine until this year. The guy that rebuilt it knew flatheads real well having raced them in the midwest during his heydays.
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| 37RAGTOPMAN | -- 10-27-2009 @ 5:04 PM |
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HI Did all the cylinders 5 6 7 8 all have 20 lbs of compression? ,this could be the head gasket,or warped head, you might have had loose heads nuts,not being retorqued after engine being broken in,? besure to check all the valve springs and the movement of the valves making sure all go up and down,and seat, when it was running did it miss only on one cylinder? you could have done a leak down test, using compressed air into the cylinders one at a time, this could have pin pointed the problem, will need a little more info, hope this helps,37RAGTOPMAN
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| woodwagon47 | -- 10-28-2009 @ 11:18 AM |
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Thanks for the reply: Only 5- 8 have low compression. I have the head off and i cannot see anything wrong with the gasket. Thought it was an ignition problem as i put new wires on it and rebuilt the distributor. It had a popping noise in it when you ran it. All the valves seem to be opening and closing. It has adjustable lifters and I checked adjustment on 5 and It was 12 and 12 I opened ex to 14 but no difference. What am I missing. Should I have the head checked. Alll cylinders are dry in the head, so it is firing.
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| supereal | -- 10-28-2009 @ 1:48 PM |
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The head gasket doesn't always show if and where it is leaking. The fact that all cylinders on one side have low compression indicates the head or gasket as the cause, or perhaps incorrect torquing, as the problem came on gradually, you say. Have a machine shop check it to be sure it is flat, and look at the combustion chambers to see if there are signs of valve interference. If the valve to head clearance in insufficient, it doesn't take long to cock valve heads, leading to leakage. At our shop, we check compression with a "leakdown" test. Compressed air is injected into each cylinder with the piston at the top of the compression stroke. The rate the pressure goes down tells us what is happening. Badly leaking valves can be heard at the tailpipe, too. If you squirt oil into the cylinder before retesting, and the compression doesn't rise, you likely have a problem with the valves.
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