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I've been scratching my head over a problem with my old 22nd series Custom 8 which I sold some years ago and myself and the current owner would appreciate any ideas.

First a little background. It was a very high mileage car and while I owned it I did some engine work. Cylinder wall taper was negligible but pistons were worn, so I did a light hone, replaced pistons, rings, wrist pins and bushings, mains and rods (crank was not removed), replaced all exhaust valves and guides, just ground the intakes. Cam was removed, polished, and the lifter bases were polished. Existing springs and lifters were retained, all this was in the 80s and the car has been a sterling runner for perhaps 20,000 miles, up until the current problem. Since my ownereship the current owner has used it very sparingly, perhaps 3000 miles in 14 years.

The car has developed an intermittent miss which usually starts a short time after the engine has been started. While the car idles, the miss will come and go, though rarely is it absent for more than part of a minute. The owner has had the carb done by Daytona, and I rebushed and throughly overhauled the distributor. Plugs, points, condensor, rotor, cap, wires and plugs are new. Timing is correct. There is no vacuum leak at the Electromatic or elsewhere that we can determine.

What gets me is how a miss can turn itself on and off. Manifold vacumm is about 19 when its running right, and fluctuates rapidly between perhaps 12 and 16 or so when it's missing. I haven't taken a compression yet, and no indications of head gasket problems. I'm just beginning to think about one or more weakened or broken valve springs but I'd sure appreciate your ideas. I've probably forgotten some important details but will try to add them as ideas come up.

Thanks for your time and thoughts.

Adding a few details. Car makes no smoke of any kind at any time. When idling normally, if you short the plugs sequentially you get the normal response, i.e. a bit of a stumble on each. When it's missing the first 2 cylinders seem to be nonperforming. At the time of the engine work the manifolds were removed and surface planed and gaskets refreshed. No indication of manifold gasket issues.

Have you been able to isolated what cylinder is missing when it starts to happen?

If it was fuel, then I would imagine that the miss would be more of a stumble across multiple cylinders. If it was electrical at the coil, condenser, or point levels, then it would also affect multiple cylinders, not just one.

If its not electrical (IE, plug not firing, plug wire arching, bad cap, wobble distributor etc), then it has to be in the valve train somewhere....like a sticking valve open if only momentarily.

I agree with you Kev, I've gradually come to the conclusion it is neither fuel nor electrical. For a while I was hopeful as the distributor shaft play was enough, borderline or worse, to make erratic performance possible, but alas, no soap as they say.

The suspect cylinders when its misbehaving appear to be #s 1&2. I do believe that the very limited use of the car may have resulted in gummy or rusted valve stems, but the symptoms aren't quite right.

I'm really enjoying this problem, good and challenging.

Does the miss also occur at a SUSTAINED EVEN speed of about 40-50 mph??? On a 8 cylinder it mite be difficult to detect.

The problem u describe is something new i have been running into over the last 4 to 5 years on my own engines.

Recently, i found that the exhaust valves in a 2.0 F ohC engine were geting real sticky for about the last 1/16" of travel to the closed position. ( COMPLETE major overhaul done on this engine 25k miles ago)

The engine would start and run just fine. Accelerate and wind out thru the gears very strong. It wasn't until the speed evened out to a sustained 40-50 mph that the miss would set in.

I removed valve cover and damned up the valve guide and poured snake oil while spinning the valve and working it up and down to clear what ever varnish or carbon had built up.

Same problem with a small 3 hp Tecumseh engine and a motorcycle engine.

Unkey one or two of the the easy valves to access. Move the valve up and down by hand to determine if the valve gets real sticky toward the full closed position.

On my engines i found that once i pulled the valve closed real fast and real hard by hand that i could not open it nor budge it by hand to open. I had to use a small hammer handle to drive it open the first 1/6" or so to break it loose. This was only on exhaust valves. Not intakes. The intakes were just fine. It took A LOT of snake oil soaking and twirling and working of the valve by hand and drill motor to get the valves freed up thru the full length of travel.

Thanks for your thoughts and observations. I'm told the problem can be present at road speeds and apparently is more often than not. Onset of the problem apparently about 2 years ago. Let me just emphasize again that this vehicle sees VERY FEW miles annually; I'm guessing here without the owner present, but perhaps less than 100 miles in the last 2 years.

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..."

My Packard V8 has ALWAYS exhibited a less than smooth idle. New timing chain, valve grind (18k miles ago) , lots of carb work and it still won't idle as smooth as it should or at least not like any of the SBC's i've owned.

Vaccum steady at 16 to 18 in of Hg. Idle screws (original Carter WCFB) has little to no effect on idle adjustment. In fact i can take the idle screws completely OUT. OR screw the m all the way in. Little to no change.

The idle seems to have become a slightly more ruff over the last 2k miles. I'm suspicious of timing chain or timing gear key position or cam shaft on this one.

Quote:
It's my party

Appreciate your thoughts Ross. He had already put a quart of Shaler Rislone in the oil, and my last advice before quitting today to make this post was for him to head up to the Interstate Parkway and blast along for a while. We've been preaching the "get it out and DRIVE it" sermon to the owner for a while.

Rislone was a favorite of an old German mechanic I worked for as a teenager - he pretty much exclusively worked on flatheat Chrysler products and was a read advocate of it. And when it came to sticky valves, they were no slouch. I've always been a bit learly of snake oil solutions in a bottle, but I guess in this case "might help, can't hurt". Perhaps I'll hear more tomorrow, we've got a rescheduled St. Patrick's day parade tomorrow. I'm thinking about putting some green paint on the whitewalls and taking the 34.