After a year of the Vette sitting (following the birth of my 2nd son)...trying to get my '89 running good again. ~128,000 miles on the car - I am the 3rd owner and have no idea on previous history - overall very well taken care of.

Prior to shutdown the car lost enough coolant to trip the low coolant light every week (about 100 miles of driving per week). It also started to run poorly - poor and uneven/surging acceleration. (I'm hoping the problems are related!)

I pulled the plugs - all looked normal except #7 - looked a bit wet. I figured it was a bad head gasket so I ran a compression test today: (motor hot and at WOT)

1 - 173; 3 - 175; 5 - 172; 7 - 170
2 - 169; 4 - 175; 6 - 175; 8 - 167

I decided to retest #5 and #7 - started it again and let it run maybe 15-20 minutes:
#7 plug - I was able to shake (what I am assuming) coolant from the hot plug onto the work bench immediately after pulling it.
Compression: #5 - 172; #7 - 190?

After I was done with the retest from #7 I was able to shake quite a bit of coolant out of the hose of the compression tester.

Any way this is not a bad head gasket? (ie intake gasket or cracked head)? I don't notice any smoke on start-up. #7 plug was smoking when I pulled it out after running the car 20 minutes.

I'm not sure if I should start tear down or run a pressure test and block test next weekend??

Thanks for the input.

 

My guess would still be a blown head gasket. There is only about 1/16" between the cylinder wall on #7 and #8 and the holes for the coolant to pass into the head. Your compression probably went up because the coolant was in the cylinder and reducing the chamber size.

A bad intake gasket is more often oil related not coolant. If the intake gasket is bad the coolant would be going into the valley and then into the oil pan.

With coolant going into #7 you eventually were running only on 7 cylinders. Hence you poor performance.

Afraid you will have to pull the heads off. Be careful when you take the head off that had #7. I am sure you will find the the gasket is blown where I indicated.

Good luck....and congratulations on son #2 .

 

Thanks John - that's what I thought as well. Yeah - look forward to hanging out with the boys in the garage as they get older...

Anyone know of a good machine shop in Houston area...please let me know.