Re: Diagnosis Needed

Posted by Ross On 2010/3/27 19:35:58

I'd say the problem is almost certainly sticky valves. Since 1 and 2 share an intake port, if one valve sticks, it will screw up the mixture of the other, and both cylinders will die, esp. at idle. And since you have hydraulic lifters, if a valve momentarily sticks high, the lifter will pump up under it, and if the lifters are good, will take a heck of a long time to come back down. I'd put a good quart of ATF in the gas tank, give the old girl a good shot of Seafoam down the carb, then take it out for a long hard drive.

Of course, the other option, which I have seen all too many times, is that the top piston ring has broken and has migrated up through the top land and is sometimes holding a valve open. "You would cry too if it happened to you..."