My relatively fresh (5k mi) carb'd '89 roller block just starting using an absurd amount of oil. At idle it's not burning it, but as soon as I hit the gas I can see smoke coming out of the tailpipe. Did I roast a ring or is it possible that my intake leak (internal/external) is allowing oil into the cylinders? I'm hoping for some good news today. I can't afford to fix it if it's a ring. I'm going to get a compression tester this week and check each cylinder, will the "push into spark plug hole" style the auto parts places rent work?
I like the screw in ones the best cause I think I get a better seal with them. But if you can get a good seal the push tight ones work just as well. If you have a choice - I would go screw in. Also, plug color is going to tell you a lot if it is just one cylinder.
The first thing is to pull the plugs to determine if it's one cylinder or all of them,if its one do a compression test and see who much(if any) difference there is between it and all the others 10% is considered normal,if you find one is a lot lower than all the others,spray a few drops of oil in that cylinder and try again,if it goes up,its a bad ring if not it could be a valve seal or guide(where the heads done?)if all the plugs are showing signs of oil(they'll look like they've got soot on them) check the pcv system, are there baffles in the valve covers? Is the pcv valve down to far it the grommet?this one happens more than you think,any signs of oil in the pcv hose is a sure sign of this,if there is oil in the hose leave the pcv valve out of the valve cover block the hole and take the car for a short drive to see if the smoke diminishes,if it does you've found the problem. sorry for the long post,hope this helps Steve
The proper way to take a compression test is: Warm engine to operating temperature ensure that the battery is fully charged pull all plugs affix throttle in the wide open position. disable or adequately ground the ignition secondary. test pressure at each cylinder. test pressure again in reverse order reinstall plugs and wires
Engine Compression Testing 1. Make sure the battery is fully charged. A battery with a low charge will give low compression readings because of reduced cranking speeds. 2. Warm the engine to operating temperature to produce metal expansion and to reduce oil drag. A cold engine will give low readings. 3. After the engine is warm shut it off and loosen the spark plugs one turn. Restart the engine at a fast idle for about 5 seconds. This removes carbon debris from around the spark plug. This will keep small particles of carbon from being blown into the compression gauge. 4. Shut the engine off and remove the spark plugs noting which came from which cylinder. A Z-car engine will run with a plug or two firing at the wrong time. It'll even accelerate and go around the block a time or two. Don't ask how I know. 5. Block the throttle open. 6. In turn, carefully insert the compression gauge in each cylinder and with the starter, turn the engine over through five compression strokes. 7. Make a note of the readings from each cylinder. What was the pattern? Does the gauge pump up fast? Is the max reading obtained after five strokes? (Very important) 8. On all low readings, retake and if it is still low, inject 30 weight oil into the combustion chamber and retest. 9. Check the spark plugs from the cylinders with abnormally low or high readings. look for carbon buildup or oil deposits. 10. Replace the spark plugs and torque them to the recommended specs. Once you've got the readings, it's time to evaluate them to determine just what the future of your engine is going to be. If the gauge pumps up slowly, such as 30, 50, 70, 90, etc. to an almost normal reading, you probably have ring problems. A general rule is that a maximum reading should occur after two strokes. If oil is added to a low reading and the pressure improves, this will confirm worn rings. A persistent low reading generally indicates valve problems. Oil lost through worn valve guides will not be determined through compression testing. Low readings can also be caused by a warped head and occasionally, two cylinders will have very low compression which can be the result of a blown head gasket. It is important to remember that the addition of oil to the combustion chamber will not improve the compression readings if your engine has burned, warped or stuck valves. High compression readings can be the result of carbon buildup or head surfacing. Generally, if the variation between the cylinders is 10 to 15 lbs., this is acceptable, but always check the specs in the manual. It would seem that equal pressure is necessary to have smooth running engine, but it's been found that with only 70% of normal pressure is enough for running smoothly. Also, manufacturers specs usually list a bottom line acceptable pressure and a good engine will usually read 20 to 30 psi over the acceptable readings.
Guess I have been doing it wrong for the last fifty years, never to old to learn though. Compression test is only a guide line to cylinder condition's, camshaft spec's can greatly effect pressures. The leakdown test is what will tell you if rings, valves and such are any good. Then there is the bore-scope to inspect for cylinder scoring etc. But for most of us, the good old compression gauge is going to work fine for analizing ring sealing or valve leaks.
stangclone and I worked it out, the #4 intake valve seal is leaking. When I romp on it, the oil pools at the back of the head, near the drain. It then gets sucked down that valve at an astronomical rate if I'm going uphill.
