ThePabst

You should see a milky pallor to your oil or external leakage with a bad head gasket.... You also may see a whiteish tint (should be bluish grey) and detect a sweet smell/taste to the exhaust during early mid warm up. A compression test does not always detect a gasket run from the water jackets to the cylinders. Small runs can actually 'seal' themselves during the compression stroke due to hydraulic action. A leak occurs, in the form of steam during the exhaust scavenge or when cold through seapage. The test shoul be done on a HOT engine... on one does that.

Are you loosing coolent?

FYI, The HG's in my Cutlass and K1500 pick up of this vintage BOTH puked head gaskets due to exposure to Dextron. Lots of info on the net about that issue.

Psychored

So what is NORMAL, temp wise? I've noticed my 89 gets up in the 220's driving in town. I'm a little concerned about it.

XR_Strider_GuY

Another quick way but not always conclusive. From a dead cold start the car with the radiator cap off. See if you can see bubbles in the surge tank. If there is this indicates exhaust gases being pushed into the coolant.

ThePabst

You want to see about 190 to 200... but they can run as high as 240 or 250 even on real hot days in traffic with AC blasting. Much more than that and you need to find out why it's getting hot. There is PLENTY of discussion on the web and in the forums about corvette heat issues. Just not allot of agreement.

The simplest, cheapest thing to be sure all seals for the hood and rad. are good. It's just foam and looses it's sprit over the years... Also be sure the factory stuff is in good working order... air dam, belt, fan clutch, fan etc. The biggie is making sure your fan shrouding is intact and tight as well as keeping all the ducting and covers in place. My C3 had a rotted core support on an otherwise nice car. (Since I was able to find several suppliers, that must be a Vette thing). It was leaking air like it's a hobby, I bought a beautiful reproduction off the net... it fit perfectly and went a long way in cooling things off for me. Waring!! Science content: All your really doing is creating hi and low pressure zones. Sealing off most of the engine compartment seems counter intuitive, and does trap heat, but forward motion creates positive atmosphere in front, and the fan and shrouds behind the core creates negitive atmosphere; That all equals air low, a good thing for us Vette guys.

I am a real tinkerer and a machinest... I put a big electric fan from a late 80's V6 Tarus on mine and made sheet metal shrouding and an air box. I also put a monster oil cooler on her with SS braded hose and a filter relocater. I know, it's all real Harry high school stuff, but 'I' think looks cool and had a blast making it and putting it in.

1fatcat

The best method I have used for testing head gaskets is as follows:

1. On cold engine, remove pressure cap.
2. Remove oil filler cap (to release escaping blow-by durring testing).
3. Remove all spark plugs.
4. Remove both valve covers and all pushrods (to ensure all valves are closed).
5. With appropriate adapter (certain compression guage hoses work great) fill each cylinder with compressed air, one at a time, and watch for rising coolant level or air bubbles at the filler opening.

There should be no bubbles or rising level. If there is either, then air is escaping the combustion chamber from a head gasket, cracked head, or cracked cylinder wall (likeliness in that order).

Use caution when filling cylinders with compressed air, as the crankshaft, belt and pulleys will rotate up to 1/2 turn when cylinder is pressurized.

I know this might sound like a lot of work, but it's not too hard to remove pushrods on a vette. You can do it without removing the valve covers or pushrods by rotating crankshaft to set each piston at TDC on the compression stroke. You need to get it perfect or the compressed air will just send the piston down and cause a valve to open. If it ends up being a headgasket, all this testing is not time waisted as you would need to do this stuff anyways.