1941 346 Valve train noise, need advice please.

[Harold]

I just finished installing a rebuilt 346 and when I started it the valves sound like solid tappets.(very loud) Since they aren't adjustable I wonder if they weren't oiling if the noise would be this bad? It does have 30-40 pounds of oil pressure. I plan on pulling the top off and double checking everything, however it all looked right the first time. Any advice would be greatly appreciated.

[Harold]

If anyone has an oiling diagram they could forward that would also be appreciated. Thanks

[Carfreak]

http://www.modifiedcadillac.org/documents/1940s/1944/1944%20Light%20Tanks%20Service/tn/1944%20Light%20Tanks%20Svc-16.jpg.html

or

http://www.modifiedcadillac.org/documents/Shop_Manuals_and_Illus_Catalogs/1941%20Shop%20Manual/tn/41%20Shop%20Manual%20-%2038.jpg.html

[Bob Schuman]

Harold,
On any engine with hydraulic lifters, it is good practice to fill the lifters with oil before installation. This is done by submerging each lifter, one at a time, in engine oil in a small can or similar container, then pumping the lifter plunger until all air has been replaced by oil. You can tell by feel when the lifter is full, it will get very stiff to move the plunger.
This very likely was not done on your engine. The lifters will eventually purge themselves of air and quiet down, and this may take one hour or more of running the engine at 1000rpm or more. I would not expect any cam or lifter damage from this on the lowly stressed valve components in the flathead.
Was the clearance between the end of each valve stem and the heel of each cam lobe checked before installing the lifters? It should be 3.000 inches, to cause the lifters to operate near the center of their range of travel. If that clearance is too far off of 3.000 inches, that can be the cause of your problem.
Bob Schuman,CLC#254

[Bill Ingler #7799]

Harold: Hopefully as Bob said running the engine will purge out the air trapped in the plunger assembly. I have included two pictures to talk about another possibility. One picture shows the lifter body and the plunger assembly. The other picture shows the plunger assembly apart. Now when these two pieces of the plunger assembly are machined, they are machined as a pair with very close tolerance. These same two pieces, comprising the plunger assembly, should always be keep together as a pair. Could all 16 plungers assemblies have been taken apart for cleaning and not mated back as pairs? This could cause excessive leak down in the plunger assembly causing noisy lifters.

[Harold]

After just two minutes run time the lifters pumped up! Whew! Thanks for responding.

[Doug Houston]

One other little question I was going to ask. What was the model year of the engine, but that came out in the last message.

When the new engine came out in 1936, the oil feed to the lifters was from the center main bearing, into the center camshaft journal, and on to the lifters. Stating it otherwise, the oil feed went through the camshaft bearing, and up to the lifters. The 1936 camshaft journal was grooved, to make a path for the oil to go on to the lifters.

Often, a new camshaft has been installed in a 1936 engine, and there is no oil going to the lifters. This is because there is no groove in the later camshafts. The oil feed to the lifters was changed in 1937, to the external pipe that remained through the end of the 1948 engine production.

When the external feed was done in the 1937 engines, there was an inline oil filter used in that feed line. Cadillac found that it wasn't needed, so it was discontinued, and never serviced as a replacement part. The parts books showed a pipe and fittings to replace the filter.

Other engines over the years used the cam bearings to feed oil through, and in all cases, found out that with bearing wear, oil fountains out of the cam bearings, and never gets to the overheads. It appears that Cadillac woke up to that mistake within the firat year, and made a good fix with the extermal feed.