I am trying to find the specified leak down rates for the OEM lifters. The factory service manual doesn't have any information and while the Tank manual describes testing of lifters it is only a comparison test against a master hydraulic lifter for which no information is given. The test fluid is listed as dry-cleaning fluid, which isn't especially helpful either. General motors must have published something somewhere but I have not been able to find it so far. Any help would be appreciated.
I have built a test rig to measure the leak down rate but I have no specifications on what it should be nor what fluid the test should be conducted with. What I do know is if the lifters leak down too fast they will be noisy and if they leak down to slow they are liable to pump up and not allow the valves to seat properly and would also be problematic in getting rid of any trapped air, so there must be some acceptable range of leak down rates.
I would also like to get some used 41 - 48 OEM lifters to test to see how they perform against the specified leak down rates. If someone has some they would be willing to part with please let me know.
Tom Beaver
There was a special tool Tom, Test Fixture no 1415655-T-1 and in the 1939 Cadillac Manufacturing Information Book (a factory floor only available book) it states,
Quote.
Total leakdown of oil past ball check valve and piston must be 4 seconds minimum with a 50lbs load. unquote.
In that era, "dry cleaning fluid" was perchloroethylene" known
in the trade as "perc" for short.
You can probably get it on line (I found it on Amazon.com from
several sources) in a quart can. It's cheap, about $5.
Mike
Steve, did the book give any clue as to the piston travel in those 4 seconds and what the test fluid was? Maybe instructions for the test fixture would give the missing pieces. Without all the parameters specified I can't repeat the test. A case in point, I just found factory specifications for 1996 Ford F-series 5.8L engines which gives a minimum leakdown time of 10 seconds and the maximum time of 50 seconds for a piston travel of 0.0625 inches using a 50 pound load and lifter leakdown fluid in the tappet. They give no clue what the lifter leakdown fluid is. I don't know what to do with the data.
Mike , thanks for the information. I will check Amazon.
Tom Beaver
I knew I had a picture of this fixture somewhere Tom. I think you're going to have your work cut out as this fixture seems a little complicated in what it's capable of doing. On the one hand, it has its own reservoir that transfers fluid somehow into the plunger and has a long arm giving a set amount of leverage. Fluid is listed as Kerosine.
How many of these tools must have been out there? Thrown in the scrap since :o
Steve, Thank you for the picture. The test rig looks to be the same as the one shown in the tank manual but it is interesting that the test fluid specified is kerosene while in the tank manual they call for dry-cleaning fluid. The interesting part is that the viscosity of dry-cleaning fluid must be a fair amount different from that of kerosene so timing for a leak-down test would be different. The test rig I have tests only a single lifter and time for the plunger to move a set distance gives the leak down rate.
Tom Beaver
The way I read the instructions timing is irrelevant. The device compares the lifter under test with the standard lifter. If the lifter under test leaks down faster than the standard it is bad, otherwise it is good.
Glen, you are correct, but I have a test rig which tests individual lifters by measuring the time a given force causes the lifter piston to depress a fixed distance. My goal is to measure a set of lifters that I have and determine which ones are any good by comparing the measured leak down times with factory specifications for what is acceptable performance. My problem is that I can't find any factory specifications or at least any specifications that are complete meaning what test fluid, what down force, what distance the lifter plunger is to travel and the maximum and minimum leak down times. I can find some of the information but not all of the information. It must be out there somewhere otherwise the lifter manufactures would not have been able to supply the correct parts. The test rig that Steve indicated simply compares a given lifter with a master lifter to determine suitability, but that master lifter had to have been created and tested first and I would like to find out what specifications it was created for.
I guess if I could get my hands on a couple of sets of used OEM lifters I could measure all of them and get a pretty good idea what the maximum and minimum leak down times should be.
Tom Beaver
What I quoted from the factory advice is the answer but one would need the factory tool to do it with. The factory specs go on to say how to prime the tool with Kerosene before fitting the plunger. You can't just make yourself a custom tool then expect to see some factory specs on how to use it.
The plunger travels such a small distance they must be talking about the full travel and the tool must have a gauge to show the 50lb pressure required on the lever. It should then take 4 seconds to fully depress it.
The only solution for you as I see it with your own tool it is to buy a new lifter, test that, and compare others against it.
Tom,
Whit Otis borrowed my leak down tester and did a lot of testing. He sent you an e-mail, did that help?
the Johnny
John,
I did talk with Whit and he sent me what information he had. He didn't have any specifications for the Cadillac lifters but he did have a complete set of specifications for Jeeps, which I will probably use, and I am also trying to get some more information from the Ford dealership since they use/have used a similar test for hydraulic lifters. Here is the the info on Jeep lifters that Whit found.
Jubileejeeps.org â€" The normal tappet will take approximately 10-45 seconds to “leak-down†using kerosene as fluid media with a 50 lb load, and a plunger travel of 0.125â€.
Tom Beaver
This morning I was looking through the 1949 Manufacturing Information for something else and found that Cadillac had a complete engineering specification for a leak down test of a 1949 lifter. This is constructed quite differently than a flathead lifter but I would think the principle is all the same and the spec would be very similar if not identical. It specifies the oil viscosity, force, travel distance and leak down time. I think that covers all of the variables. The fluid is a kerosene and oil mixture, 32-34 seconds viscosity (Saybolt) at 100F. The plunger is loaded with a 50 lb. load and the time for a plunger travel of 0.125 inch is 12 to 40 seconds. See first attachment for a more complete description.
The second attachment is an explanation of lifter operation and source of noise. Just some very interesting stuff. Lifter noise is actually the valve hitting the seat. It is not the lifter or any of the valve train.
Brad,
Thanks so much that is exactly what I was looking for.
Tom Beaver
That seems to be at odds with the 1939 Manufacturing information Brad, which states 4 seconds??
Steve, The trouble with your reference is that it is not a complete specification so it's hard to compare the two, but the number they give for the minimum leak down rate certainly is different. From what little fooling around I have done with measuring leak down rate so far, I would say that a lifter with a 4 second minimum time probably would be noisy in operation. The maximum leak down rate isn't given but I think this is equally important because if the lifter is really tight they can tend to pump up and then the valves don't seat completely and it would also take a really long time to clear any trapped air. Also the source that Brad quoted seems to be in pretty good agreement with the specification that Whit Otis found for the jeep engines. It seems to me that we really don't have a very good record of what went on when they designed these things 80 years ago. Anyway it gives us something to do now to keep us off the street.
Tom Beaver