Packard Forum Index » Pre-War (1899-1942)

1940- 356 engine. Pressure takes 20-30 seconds or so to come up to 40-50lbs at idle.Pressure stays good from then on. Removed oil sending unit to check for flow. Oil Flow coincides with slow pressure build up at start up. Only thing I can of is a blocked screen on the pump. Any other ideas before pulling the pan?
Bill

Mine acts the same way. Takes a few secs to work its way up and then stays at 40, unless I'm sitting in stop and go traffic.

It's typical on any engine at startup for oil pressure to accumulate rather slowly, or at least not instantaneously and is dependent on several things including the temperature and viscosity of the oil and the type of oil pressure gauge. And a direct-reading pressure gauge (bourdon tube type) will respond instantly but the electric sending units typically have a lag and slower response. Your observation of 20 seconds or so to reach full pressure seems typical and I don't know that it's indicative of any problem.

That said, dropping the pan to clean it and the intake screen is always a good idea especially if you don't know that it's been done recently.

Dear Bill:

That is slow. I would drop the pan and make sure the pick up isn't loose and sucking air. Especially since symptons indicate a mechanical gauge would also be slow.

When new the fast idle cam on the carburetor had the motor spinning pretty fast upon start up so oil pressure should be instantaneous. On senior models this symtpom indicates a clogged capillary tube to the gauge due to plating.

Good luck with your car.

I blew out the tube to the sending unit and put a screwdriver in it and it seemed clear. Do you know how far in the capillary tube goes in before it connects to main oiling system? Is there a place to get a diagram of the actual flow of oil through a 356 engine?
Bill

This is out of 46 fact book and I believe a fairly typical oil flow in all the S-8 engines. Some of the senders come off the loop on the drivers side where the filter takeoff would be. Various plumbing was done on the filter depending on year. Others like this one have the pressure taken off the main bearing supply.

I don't believe there is any length of capillary tube inserted -- just a fitting screwed into a location with the tube soldered or otherwise attached.

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Here's an illustration of a 356, Bill, for a 1940. The route through the oil filter may be reversed on your car.

edit: Use a mirror to see if there is a stamping on the bottom of the oil filter canister that says INLET or OUTLET

Joe

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Thanks for the diagrams. The filter on my 356 is on the opposite side of the block. Opened and cleaned out the filter canister as it doesn't drain completely. Ran the engine with the top of filter canister off and the filter out. Not like modern cars, as the flow is very low. There are only two small feed holes in the stand pipe in the center of the filter and the feed to the filter itself is teed off the oil sending unit and is only 1/4" tubing.
Bill

Now wait a minute. Look at the diagram in post #7 above titled " 1940oilflowweb.jpg". It shows 2wo oil lines connected AT the oil filter, one at the bottom of oil fitler and one at the side of the oil filter near the top. But EACH of those 2wo oil lines are connected at their other ends to 2wo different oil galleries inside of the engine.

SO does that mean that one of the main oil galleries is pressureized by oil comming thru the filter FIRST??? Which means that if the oil filter were completley removed form the engine then one of the oil galleries would not recieve oil???

In 1940 there were several versions of the 356 filter flow. Originally it started out with all the oil to the lifters flowing thru the filter as the drawing shows. Starvation and noisy lifters was found to be an issue as filters dirtied so a special filter with a bypass valve was made available. Apparently that was not totally successful so a different flow path was chosen with lifters getting a more direct feed. Improvements were still needed so the plumbing was changed again for 41 and later engines. All this is documented in the service counselors.