1989 460 compression
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From: Sacramento USA
1989 460 compression
Hi,
I have been having a problem with misfiring. By pulling the wires off the distributer, we found the second cylinder back on the drivers side wasn't firing. After testing that cylinder, we found to have between 110 and 115 compression. The other cylinders are running about 135 to 140 compression.
Does anybody have any ideas on why this cylinder is so low? Are there any other tests I can do?
Thanks,
Greg Frank
I have been having a problem with misfiring. By pulling the wires off the distributer, we found the second cylinder back on the drivers side wasn't firing. After testing that cylinder, we found to have between 110 and 115 compression. The other cylinders are running about 135 to 140 compression.
Does anybody have any ideas on why this cylinder is so low? Are there any other tests I can do?
Thanks,
Greg Frank
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From: Nevada
1989 460 compression
Put a couple of tablespoons of oil in the low cylinder before you test it. If the psi comes up, it's a pretty good indication of failing rings. If not, you'll need to do a leakdown test to determine if the problem is a valve or valve guide.
When you say not firing, is it getting spark to the cylinder? If it is, I'd say you have a burned valve that won't let the cylinder hold the mixture for combustion.
When you say not firing, is it getting spark to the cylinder? If it is, I'd say you have a burned valve that won't let the cylinder hold the mixture for combustion.
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From: Hawthorne USA
1989 460 compression
[updated:LAST EDITED ON 29-Jul-02 AT 01:09 PM (EST)]If you have a cylinder leak down tester you can put your piston at TBDS and put some air to the tester. by doing this you can find out if you have a bad valve or if your rings are shot. If the motor is old you could have some carbon on a valve. and that would not let it seat properly. if you do have a tester or can get one, here is what to look for.
when you apply the air take off your oil cap. if the sounds like it is coming out of there your rings are bad. if it sounds like its coming from your carb your intake valve has a problem, or if it is coming from your exhaust you have a exhaust valve problem.
or you can try a can of restore. you can buy at any parts store and it only cost about 6 dollars. I have had good luck with it on high millage motors.
sorry so long,and good luck.
jeff
when you apply the air take off your oil cap. if the sounds like it is coming out of there your rings are bad. if it sounds like its coming from your carb your intake valve has a problem, or if it is coming from your exhaust you have a exhaust valve problem.
or you can try a can of restore. you can buy at any parts store and it only cost about 6 dollars. I have had good luck with it on high millage motors.
sorry so long,and good luck.
jeff
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From: Sacramento USA
1989 460 compression
After pulling the wire, you could hold it an inch or so from the post and see the spark jumping to the wire. When we pulled the other wires, one at a time, there was a noticible difference in the idle. This one made no difference.
The engine was rebuilt a year or so ago, but I don't think they did a very good job. It leaks oil all over the place
I will try the oil in the cylinder and see if it holds.
Thanks!
Greg
The engine was rebuilt a year or so ago, but I don't think they did a very good job. It leaks oil all over the place
I will try the oil in the cylinder and see if it holds.
Thanks!
Greg
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Joined: Jan 2000
Posts: 966
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From: Crooked River Ranch, OR
1989 460 compression
The differance in your compression test isn't really that bad to cause a missfire. Try swapping a couple of plug wires around to see if it's a bad wire. Put a new plug in the missfiring cylinder to see if it's the plug. Check the dist. cap to see if there is arcing inside the cap or a terminal is corroded...Deen
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