| woodwagon47 | -- 03-01-2010 @ 3:07 PM |
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I have my engine out of the car due to a popping noise that occured last fall. The engine was rebuilt about 5 years ago and has ran great until now. I took the heads off and pulled all the valves, replaced 3 guides, and refaced the valves. They looked good but i did it anyway. I had the heads resurfaced. This engine has run engine great since it was rebuilt. A friend said I could have a cracked block, It starts popping after it gets warm. The heads were not bad but they were warped a little. Before I took it out I ran a compresssion test, number 1 and 4 20 lbs and the rest about 80. no oil in cylinders, seats look good to the eye. any ideas? It was not using any oil and carried good oil pressure.
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| Pauls39 | -- 03-01-2010 @ 5:29 PM |
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When you checked the compression did you check it wet with some oil in the low cyl? This would seal the rings. If they were still low I would suspect a valve problem. Did it pop back through the carburator or out the exhaust? We will need more information. Post back when you can. With the information at hand,I would suspect bent or sticking valves or worn guides.
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| woodwagon47 | -- 03-01-2010 @ 7:41 PM |
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I checked the compression dry, no oil in the cylinder, It had 3 bad valve guides that I have replaced. The engine has been converted to later valves and one piece guide. When I took the heads off the cylinders were dry that is no oil up in them. The valves seem to be straight not bent. The guides came right out, it has adjustable lifters and the clearances were good. One thing we noticed is that the rotor button has a lot of play in it, but none in the distributor. As I said the heads have been resurfaced. It is popping back through the carburetor. It has never backfired. It will idle fine, then when you get it out on the road and up to temp it starts popping. Your lucky to get it up to 50. After sitting for awhile I mean a week or so its a little hard to start but after you get it running it starts right up. Right now the motor turns over easy on the floor. with a socket on the crankshaft pulley. It has an electronic ignition on it and all new wires. I sent the electronic distributor back to Philbun for testing and they said it was fine. igniti
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| supereal | -- 03-02-2010 @ 10:13 AM |
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This is a long shot, but late last year we had an engine in our shop that had odd compression readings on two cylinders. The owner was told that it had been "rebuilt" just before he bought the car. It, too, was popping. We found that two of the replacement valve seats were loose when the engine was warm. Whomever did the job overcut the block, and tried to secure the seats by staking the edges. Another common cause is weak or broken valve springs, often hard to spot, or failure to completely seat the valve guide forks. When we convert a early engine to straight stem valves, we cut an extra seal groove in the guides to be sure they don't leak. Also, check to see that the crankshaft key holding the gear that turns the timing gear is intact, and hasn't sheared or swedged. That will interfere with the timing, also a cause of popping and backfiring.
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| Pauls39 | -- 03-03-2010 @ 5:39 PM |
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Just a guess but I would look at this mainly as a valve problem. Like Super said check the valve springs. We have seen a mix of short and long springs with assorted keepers, early springs with late rotaters, they don't mix well. Be sure yours are a set and that the installed spring hight is correct. You may need shims to get the correct installed spring lenght and pressure. Lap all the valves/seats to ensure good contact. It may be a separate issue, but that rotor should be tight. Replace it if need be. Some of the parts made off shore leave a lot to be desired.
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