1966 6 cyl. 240. I posted this in the 66 section then realized i should have posted here.

I recent bought this project truck. Before i spend too much time on it wanted to check compression.

5 of the 6 cylinders are within 5% of 110. The sixth is at about 75. I put some oil in the low cylinder and the compression went up to about 110.

This truck has not been running for about 15 years. I got it started enough to notice it needs a water pump and shut it down.

This indicates a ring issue and not valves, right?

Suggestions? I did not want to do a rebuild. I would like to drive it.

Thanks
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You are correct.

 

Yes it could be the rings but it could also be due to it not being run in 15 years. If you checked the compression before running it then I'd run it through at least one warm up then check again.

 

Or squirt something like Gumout into that cylinder, let it sit a while and run it a little to see if compression improves. Then change the oil, now that it's been diluted with Gumout, and you probably should anyway after sitting for 15 year.

 

Thanks for the help. i will report back.

 

Well, I finally got the truck running for a while. I checked the compression in the one low cylinder, and it came up to match the others. Thanks for the help.

 

Good. Now install the turbo and you are ready to go!