I bought a 1970 Corvette, 350/300 HP Turbo 400 car about six years ago. Documentation shows it only has about 71,000 miles. The car has an inordinate amount of blow-by. When I first picked up the car it was really bad, but now that I drive it every month or so, it seems to have gotten a little be better. If the mileage is correct, that would indicate the car has done a lot of sitting around over the years.
If the mileage is correct, then I would suspect that the rings are probably stuck as opposed to being worn-out. If that is the case, then is there a way to un-stick the rings without tearing into the motor? AJ
Submitted by: Andy Bedoian
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I had a similar issue, but not exactly the same, a year ago. I'm not sure this would apply to your situation. My #8 plug kept getting oil fouled and would misfire under high load conditions. Valve guide seals? Oil ring not seated? Before tearing the engine down too far, I pulled the intake manifold and found that the intake gasket at the lower part of the port had been sucked in so that there was a direct leak into the oil valley. So that cylinder was pulling oil vapor directly into the intake port. On top of that, #7 cylinder had a leak at the top of the port, so it was running somewhat lean. The gasket was a FelPro 1205 which had been on the car for about 15 years. FelPro now makes that same gasket with a steel core (just like the GM originals). That fixed the problem.
Did you run a compression test to see if a certain cylinder has an issue. I agree with the other respondent not to add goo to the engine, but on a Chevy V6 (60,000 miles) that had lower cranking compression (120 psi), I used a product called XADO and it worked as described. After 1000 miles, cranking compression increased to 165 psi although admittedly,I did not notice a blowby problem on this motor, I just ran a compression test and thought the numbers were on the low side.
A great PCV valve I have used is made by ME Wagner, and it is a dual flow adjustable and will scavenge the crankcase much better than a stock piece.
Not sure if this will help you, but just some ideas that may apply.
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D on
4/3/2016 3:06:00 PM
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Wow I?ve heard of making assumptions before AJ but you take it to a whole new level. I have zero idea how mileage directly correlates to wear. I guarantee you we can put 100K worth of wear on an engine in a couple days at the track. Actually it isn?t impossible for us to kill an engine during testing. We also see cars with very low miles destroyed by missed oil changes. This is especially true on cars with ultra low miles because they often get serviced based on miles rather than elapsed time. This leads to moisture contamination which kills piston rings or bearings during their infrequent use.
I would first find out what?s causing the problem then repair accordingly. First is the blow-by really excessive and where are you seeing it? Your crankcase breathes through a PCV (Positive Crankcase ventilation) system so nothing should be visible except a possible accumulation of oil in the air filter. Begin by testing the amount of air flow at the end of the inlet tube at the air filter. There should be enough vacuum (suction) that it will hold a standard business card to the end of the hose at idle. This is not the PCV hose but rather the inlet hose usually to the right valve cover. If the suction is low check for blockage in the PCV hose and fittings. If none is found remove the valve covers and look for crud in the oil splash baffles.
Finally if there is no blockage anywhere in the PCV system consider having a BG Products engine oil flush performed. We have used this system on some of the Northstar Caddy?s and problematic Hondas where they used a quart of oil every fifty to seventy five miles and brought them back to a quart in one to two thousand miles. But whatever you do don?t buy a can of glop off the parts store shelf and throw it into your oil as the results could be catastrophically bad.
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Anonymous on
3/19/2014 12:35:31 PM
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