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29 Pontiac valve spring cups


Guest Sam_ca

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Guest Sam_ca

I recently acquired a 1929 Pontiac Landaulette which appears to overall be in fair condition. After minor fiddling it started and ran without much enthusiasm but also without overheating or any outward indications of distress other than being lethargic and a persistent miss. I was not expecting it to be a rocket sled so the funky performance didn't give me the warning it perhaps should have. During my first drive out of the neighborhood I started getting some serious misfiring and it seemed increasingly unhappy. So, I started looking into things.

Pretty quickly I found that the exhaust valve for #3 had dropped and the spring was free-floating along with the valve. Some creative wrenching resulted in getting all 12 valves out and cleaned up. The root of the problem looks like damage to about half of the valve spring cups, with one being completely destroyed - no sign of the center part. Looking closer, I noticed that some of the valve springs are tighter on one end than the other, and those cups which were undamaged were in the tight ends of the springs. Furthermore, two of the tappets were single piece inserts with thread lockers, and theo others are all bolts ground flat with lock nuts.

So, what should the valve cups and springs look like really? I'm convinced that there are a mixed set of cups, tappets and springs in the engine and some sort of incompatibility is the cause of the failure.

Is there a source for new valve spring cups or is there an acceptably close equivalent? I have exhausted my short list of parts suppliers with no luck. Worst case I suppose I can take them to a machine shop and just get a set turned. I have about 6 good ones, and the rest look like they were attacked by an angry honey badger.

Thanks!

Sam Brown

Edited by Sam_ca (see edit history)
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Guest Sam_ca

Update: Visited my local engine builder who recommended using a modified modern style set of keepers for the valve springs. He found a set that are for the correct diameter stem and could be turned down to match the spring diameter. Anyone try this?

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Ichanged the valves and keepers on my engine 320,000 miles ago and had no trouble until three years ago when two of the original cups split leaving the flat part on the valve stem and the cuped part around the tappet. I couldn.t find a suitable replacement so the local machine shop remade my cups using a hardened washer for the bottoms. It has been 36,000 miles since with no trouble.

I don't think that any modification really matters as long as the original dimensions between the valve seat and camshaft remain the same.

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