Dealing with an engine with oil blow-by - hoping for some thoughts and coaching on options |
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Dealing with an engine with oil blow-by - hoping for some thoughts and coaching on options |
Tdskip |
Jun 25 2019, 01:13 PM
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#21
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Advanced Member Group: Members Posts: 3,686 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None |
OK - so here is the scoop on the '74 AZ car that has me about to learn new things.
This is the car that has the 2.0l case with 1.8 heads. Runs strong, good pulling power, no bad noises, and has good oil pressure. Came to me with a recently put together engine with no guarantees but believed to be redone heads and fresh bottom end. Price was right on everything so I bought it, no regrets. The issue I am seeing is that the engine has too much blow-by. After a short time (under 30 miles) it started smoking very noticeably from the breather and blew out the oil seal on the breather tower. Since then I've changed the oil and done more heat cycling and it's smoking significantly less (barely noticable now) but I still have too much blow-by. I don't think I have much to loose by driving it some more and seeing if the rings seat better but I am working on the expectation that isn't going to work. Assuming the most likely case, which is that the rings don't seat any better, I believe I would need to pull the heads and pistons off and start again. Yes/no? Should I be thinking of just replacing the jugs and pistons with a new set from AA or do these clean up (in general). I believe replacement is the usual approach these days. I think I would plan to send the heads out for servicing as a precaution so I know I have good ones with good oil control going back on. Assembly from this point should be pretty straight forward I'd think? Thanks, appreciate the continuing education here. |
jcd914 |
Jun 25 2019, 10:40 PM
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#22
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Advanced Member Group: Members Posts: 2,081 Joined: 7-February 08 From: Sacramento, CA Member No.: 8,684 Region Association: Northern California |
Couple thoughts:
Since you don't have history on the engine there are too many unknown variables but it might still be seating in the rings and improve with milage. It can easily take a couple thousand miles to fully break in an engine. You say it has a single Weber carb and runs well, so the engine has much more potential since the single carb on a flat four works poorly in general, meaning with better induction it could run really well. The long flat intake runners with the single carb promotes air fuel seperation between the carb and the heads and fuel falls out of suspension. Warm climate help keep fuel in suspension but is not enough. Commonly the single carb is set up overly rich so there is still enough fuel in suspension for the engine to run on. One of the potential issues you maybe dealing with is too much raw fuel getting to the cylinders from an overly rich mixture to make the carb seem to work. The concern here is with the excess fuel washing oil off your cylinder walls leading to rapid piston, ring and cylinder wear. Test, don't guess. Do compression test AND leak down and see what is going on. If you tear down latter you will still want to know what the compression and leak down were before you took it apart. Nothing like guessing about issues before you reassemble. Jim Note: No 1.8l 914 engines have EGR ports in the heads. Late 2.0l heads have Air Injection ports but that is just the 75/76 2.0l engines. |
tejon007 |
Jun 26 2019, 12:57 AM
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#23
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Newbie Group: Members Posts: 45 Joined: 10-February 10 From: Northern California Member No.: 11,344 Region Association: None |
Couple thoughts: Since you don't have history on the engine there are too many unknown variables but it might still be seating in the rings and improve with milage. It can easily take a couple thousand miles to fully break in an engine. You say it has a single Weber carb and runs well, so the engine has much more potential since the single carb on a flat four works poorly in general, meaning with better induction it could run really well. The long flat intake runners with the single carb promotes air fuel seperation between the carb and the heads and fuel falls out of suspension. Warm climate help keep fuel in suspension but is not enough. Commonly the single carb is set up overly rich so there is still enough fuel in suspension for the engine to run on. One of the potential issues you maybe dealing with is too much raw fuel getting to the cylinders from an overly rich mixture to make the carb seem to work. The concern here is with the excess fuel washing oil off your cylinder walls leading to rapid piston, ring and cylinder wear. Test, don't guess. Do compression test AND leak down and see what is going on. If you tear down latter you will still want to know what the compression and leak down were before you took it apart. Nothing like guessing about issues before you reassemble. Jim Note: No 1.8l 914 engines have EGR ports in the heads. Late 2.0l heads have Air Injection ports but that is just the 75/76 2.0l engines. Not true...I had a '72 with EGR heads (from a bus). Ok, so it's not normally an issue, but he said there was an unusually large amount of blowby. Shouldn't have even mentioned it... Mixed and matched parts from unknown motors...could have heads with EGR ports as one possibility. If so, what was done? It's anyone's guess. Inspect and as we both said, perform compression and leak down testing... So, whatever...less guessing and more testing. My Best |
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