<VV> 140 Engine: Dropped Valve Seat or ? ? ?
corvair at frontiernet.net
Mon Sep 11 18:37:17 EDT 2017
I bought a '65 Corsa in 1995 to use as a spring, summer, and fall commuter. It was in decent shape, but not worth restoring without spending a lot of money on rust repairs. About a month after buying it, I was synchronizing the carbs when it suddenly started running roughly. I noticed the choke pull-off on the passenger side head was "fluttering." When I went to turn the car off, I noticed the vacuum gauge fluttering also. I suspected a dropped valve seat. After I took off the head, there was the seat dangling on the neck of the #5 exhaust valve. Fortunately, no damage occurred. I took the head in to a shop experienced with aluminum heads [Porsche & VW], and they replaced the seat as well as the valves and springs which I had delivered to them from Clark's. I dimpled the aluminum evenly around each seat before reinstalling it hoping to prevent it from reoccurring.
After driving the car for 22 years and 90,000 miles without any major problems, it started to "act up" again. I was leaving a suburban plaza and accelerating up to the 40 MPH speed limit when the engine suddenly started running roughly. I thought it might be the ignition system. After arriving home, I shut it off and looked over the plug wires, distributor cap, and rotor. I didn't see anything. and didn't do anything else to it that day. The next morning, I started it, and it ran normally, so I started to drive around my neighborhood. After a few miles, the missing returned, so I returned home. Leaving the engine idling, I looked it over and saw the passenger side carb choke pull-off fluttering. I thought, "Here we go again." I shut off the car and let it sit. I was busy with my Lakewood and didn't want to do more than one project at a time.
A few days later, I took off the valve cover on that side and turned the engine over by hand as if doing the cold valve adjustment. I discovered that #3 exhaust rocker arm was loose and the valve spring appeared to be partially compressed. A few weeks later I needed to move the Corsa so I could get my Lakewood out. The Corsa started and ran normally with the exception of the tapping from the loose rocker arm. I ran it for 10 minutes at 1000 RPM fast idle and then dropped it to idle for another 5 minutes. No problem except for the rocker arm tapping.
Does anyone have any suggestions for other things I can check that could cause this problem? I don't understand how a seat could re-insert itself. Could the valve be sticking in the guide? Can anything be done about it other than taking off the head?
Any ideas would be appreciated. I know I've had my money's worth and then some from the car, but it's such a great driver that I'm somewhat sad at having to give it up.
I have more respect for the fellow with a single idea who gets there than for one with a thousand ideas who does nothing. - Thomas Edison
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