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post #1 of 4 (permalink) Old 08-27-08, 06:28 PM Thread Starter
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Compression test: low in 1 and 2 after gasket work

Here is the update: car still running, but still rough at idle. Did a pressure check today, and got from between 100-150 psi for cylinders 3,4,5,6. 1 and 2 (the cylinders with the misfire codes) only come up to 60. Bad news. I did the oil check where you add a few drops of oil to the spark plug holes, and the pressure rose to 75. So that means there is some piston ring wear, but I don't think that's the main problem. When I did the head gasket replacement, I pulled the heads and took them to the machine shop where the machinist said that the rear head (1,2,3) was out .006 which was the outermost range of tolerance, but still in tolerance. So he re-surfaced them and he pressure checked the valves and said they were ok. I'm 99.9% sure there was nothing wrong with the re-installation of the gasket and heads. I torqued them in the order and to the specs provided by Ford. My main question is this: assuming the machinist didn't screw up the resurfacing, is it more likely that I've got a problem in the block or a problem in the valves? I'm leaning towards the valves, thinking maybe the valve seals are cooked which may cause the loss of compression. I don't think it's likely that the block would be worse than the heads and visually inspected it for cracks and didn't see any. What else should I be thinking about here?

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post #2 of 4 (permalink) Old 09-06-08, 11:38 AM
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Re: Compression test: low in 1 and 2 after gasket work

I am having the same problem. Someone please help us!
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post #3 of 4 (permalink) Old 09-06-08, 03:29 PM
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Re: Compression test: low in 1 and 2 after gasket work

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Originally Posted by jdhgator View Post
Here is the update: car still running, but still rough at idle. Did a pressure check today, and got from between 100-150 psi for cylinders 3,4,5,6. 1 and 2 (the cylinders with the misfire codes) only come up to 60. Bad news. I did the oil check where you add a few drops of oil to the spark plug holes, and the pressure rose to 75. So that means there is some piston ring wear, but I don't think that's the main problem. When I did the head gasket replacement, I pulled the heads and took them to the machine shop where the machinist said that the rear head (1,2,3) was out .006 which was the outermost range of tolerance, but still in tolerance. So he re-surfaced them and he pressure checked the valves and said they were ok. I'm 99.9% sure there was nothing wrong with the re-installation of the gasket and heads. I torqued them in the order and to the specs provided by Ford. My main question is this: assuming the machinist didn't screw up the resurfacing, is it more likely that I've got a problem in the block or a problem in the valves? I'm leaning towards the valves, thinking maybe the valve seals are cooked which may cause the loss of compression. I don't think it's likely that the block would be worse than the heads and visually inspected it for cracks and didn't see any. What else should I be thinking about here?
Did you replace the Plugs after the Head Job?? This may have a little effect in this. Also your are correct if the Valves are worn, or not seating correctly will cause this too.
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post #4 of 4 (permalink) Old 09-06-08, 04:09 PM
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Re: Compression test: low in 1 and 2 after gasket work

Quote:
My main question is this: assuming the machinist didn't screw up the resurfacing, is it more likely that I've got a problem in the block or a problem in the valves? I'm leaning towards the valves, thinking maybe the valve seals are cooked which may cause the loss of compression.
Thats a huge compression drop. Being those cylinders are side by side it would almost have to be the head gasket, cracked head or cracked something else but I don't thinks it's the valves or valve seals.
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