[RedGT350LuvR]

A little history-I’ve had my 65 K-Code for 3 yrs. and I’ve not been in the motor and don’t know when it was last worked over. Since I’m going to do the Mustangs Across America, I want to get it right. I did a compression test and numbers 1 thru 6 all were within 10% of each other with 5 cylinders being 170 and one 160. #7 was only 130 and did not come up any after adding a tsp. of 30 wt. so I know I have a valve problem there. #8 was only 130 but did go up after adding the oil. My question is-Why only 1 cylinder showing ring wear? The first couple of yrs. I had the car, if I drove it for some time at real low RPMs like in a parade, I would start seeing white looking smoke after a while. The temp. would never go above about 190. Last summer it got to were I can’t drive it at slow speeds at all without it running hot. I put in a new thermostat and added an aluminum radiator (already had an elect. fan and I don’t think the bottom hose is collapsing) and it didn’t help any. Is this a completely different problem or is it related anyway to my compression test results? I would definitely appreciate any advice on what I should do.

[Ivy66GT]

Could well be you have some broken rings. Overheating tends to cause broken rings since the rings expend, the end gap disappears and the rings butting against themselves break the rings. It can happen in only one cylinder or all of them. If the rings are broken up bad enough oil may not help the compression reading.

Do a leakdown test. That is the only way to know if its rings or valves.

[cindys_sn95]

are you losing any water? you could have a small crack in the head, or weak gasket.

[Dustysdawg]

#7 and #8 are both 130. Coincidence? I doubt it.
Sounds like a bad/blown head gasket between the two cylinders, or some type of crack between the two cylinders.
I would pull the heads and check everything out. If it is the gasket, I would have the heads surface flattened, then put on new Felpro head gaskets. If it is a crack, that is a whole other issue.

The over-heating problem is most likely related

[RedGT350LuvR]

Oops...sorry, a little typo on my part-#7 is 130 and #8 is 150. I've not had any real water loss but with the white looking smoke, I really expected to find side by side cylinders to have the same reading indicating a head gasket problem but that wasn't the case and as I mentioned, #8 came up after adding the oil and rechecking where #7 didn't. Do you still feel it's head gasket or a crack?

[Dustysdawg]

With the low compression and the over-heating problem, I would suspect the head gasket or a crack. Generally, ring problems don't cause overheating. But, overheating can cause ring problems. Have to find the overheating problem first.
There are two types of white smoke. White/White which is water, and White/blue which is oil. Did you notice if the smoke had a blue tint?

[RedGT350LuvR]

I didn't really notice a blue tint but I couldn't swear that it didn't have a little. I just don't really remember any blue tint.