If in fact you can successfully make a correlation between casting numbers and the various finished part numbers that were derived from a single casting, it will be quite an achievement. These casting numbers which appear on cylinder heads, oil pumps, etc. have confused a lot of folks over the years, thinking they are part numbers. Good luck on your venture.

I assume you're familiar with the Service Counselor issue which discussed the change from machined to cast domes on the (1955) 320 engines and the resultant change in casting numbers? It notes that the characters "CD" will be added to the casting # 440854 for cast domes (though it was not added for the earliest cast heads). The cylinder head with the machined domes was 440689.

The casting number on my spare 56 engine (Utica #D-6748)which I believe to be unmolested is #6480408CD, as is the number on my 56 Caribbean (Utica #C-1137). Hope this helps.

PS - I looked long and hard at the last digit of the 56 casting number and believe it is an "8", not a "6", though it's less than perfectly clear.

I assume you took the compression with all the plugs removed and the choke valve held open? And did you do it "dry"? If so, I'd add a tablespoon or so of oil into each spark plug hole, crank the engine over several times, and then take it again. If the readings increase significantly it indicates ring and/or cylinder bore wear, if they don't it indicates leakage at the valves which is far easier to deal with. L-head engines of this vintage typically need a valve grind every 30,000 - 50,000 miles, sometimes more frequently if driven consistently at higher speeds.

Compression ratios for the 1941 Six were 6.39 std and 6.71 optional and I'd guess that 1940 was about the same, so I'd think compression readings of about 90-95 psi should be expected.

I can't give you any specifics, perhaps others will chime in with first-hand experience, but I can tell you there are people who have removed the torsion bars without the special tool. Cementing eyelets deep into concrete floors, using chains and cables/winches, etc. come to mind. So it can be done.

Solex (tinted) windshields were made available starting in 1952. And to those who have had to buy a new windshield for a 55/56 Caribbean, $325 would be the steal of the century.

No, I don't think so. 55T-16 refers to holes in the shaft itself, while I believe PackardV8 was speaking of the holes in the rocker levers themselves.

PackardV8 asks: Do the rocker arms have an oil squirt hole in them directly above the push rod????

I don't know, I checked the valve area oiling some years back before I realized that there were two different style of rockers, w/ and w/o those holes. And I don't think I've ever read in any of the STBs or SCs anything about that difference. Do you have any reference or information about them?

My car has the dual Rochesters, so I'm giving you this based on what I think the single carb model is like. The vacuum line from the intake manifold runs in a steel tube to the rear of the driver's side cylinder head, and there it is held down to a bolt in the head that also includes the body/engine ground strap and the steel vacuum line from the crankcase. From there both continue with rubber hoses up to a junction block on the cowl near the wiper motor. The block also connects via rubber hoses to the wiper motor and the washer head. Of the 2 vacuum sources, you'll have to grope around a bit to see which comes from the manifold and which from the crankcase. Temporarily plug the one from the crankcase with a bolt or similar.

The wipers should still give decent performance except under heavy throttle load with the crankcase pump disabled. If not, more than likely the wiper motor either needs internal lubrication (I use Mobil Vacuum Pump oil) or servicing. My crankcase vacuum line is intentionally closed off and my wipers are excellent under all conditions except full throttle when they slow down a bit.

I agree with Jack that it doesn't have the correct symptoms for a valve seal problem. Why not take a compression test first before you much deeper into it, and let us know the results. Also how about a manifold vacuum test at idle? How much vacuum and how steady is the reading? And how about running a rifle-bore cleaning rod down the oil return holes in the head - very important! These holes are not overly generous is size and if partially restricted you can get quite an accumulation of oil in the head which could then overwhelm the valve/guide clearance.

And one other thing to do first, take the vacuum line from the vacuum pump in the crankcase (joins to the vacuum block near the wiper motor) and remove it and plug the end. I think there's a very good chance that the check valve on the side of the block has failed and you're pulling oil from the crankcase vacuum pump directly into the intake manifold. Happened to me, looked like I was the mosquito exterminator coming down the street.

Comments about lack of lubrication to the valve area doesn't agree with observations on my 56 Caribbean with 90,000 miles. I don't know the entire prior history of the engine, but think it has never been opened. Though the car is a late one (#254) the engine is an early one (C-1137); it doesn't have the valve spring baffles and the valve area is generously oiled when running, enough to spatter all over the inner fender in just a few moments of running.

No, I don't believe that is correct, though the Caribbeans were in fact delayed because of the seat issue and apparently it proved to be too much handwork to fit the underseat heater, thus they were not installed although allegedly standard equipment. According to an analysis of the build slips, the 3 cars that had the underseat heaters were not early cars, they were #s 1096, 1119, and 1230. It would be interesting to examine one of these and see just how the heater was fitted because looking at my own Caribbean convertible, it wouldn't fit w/o alterations to the floorpan.