Cleaning and repair of hydraulic lifters

[Author nameAuthor names are only available to PAS members.]

I have been working on getting my ’35 hydraulic lifters to seal and have some notes and perhaps tips for others. The PASB’s have many discussions over the years on how to check the lifters, both original procedures from the factory and tips from restorers. Unfortunately I found some of the details could use with some modification and elaboration.

First, this entire discussion relates to the plunger and the ball check valve assembly that slips into the tappet body itself (I call the tappet body the piece actually rides on the camshaft). Just to make things more interesting, the PASB’s refer to 2 different designs of tappet, the original that was used from 1933 to 1935, and the second design used for ‘36’38. The second design was adapted by Packard and Cadillac after Pierces’ demise, and WWII war surplus plungers built for the Cadillac powered “Stuart” light tank are still available through Egge. Those plungers are apparently interchangeable with the ’36-38 Pierce by modifying the top plunger cap height, and therefore ‘36-‘38’s can avoid the repair issue by replacing with NOS.

The two designs can be identified by the latter having exposed springs below the plunger cap and the 1st design having springs below in the tappet body. My tappets are neither design, having exposed top springs but having the bore dimensions of the 1st design, suggesting that the late ‘35’s had an interim design change and are not interchangeable with the Cadillac NOS. This made it necessary to use the existing tappets and repair as needed.

The basic method for checking the lifter is to put a rubber hose over the check valve end of the plunger and try to blow through it while immersed in gasoline up to the oil feed holes halfway up the plunger. A good check valve is indicated by having no bubbles appear. There are a few mitigations from the Pierce literature, maybe a few bubbles are acceptable and the check ball can have a drop of gasoline on it while doing the check (dry is the hardest condition for this test). In the member’s forum Ed Minnie indicated that this test isn’t foolproof, his experience was that the ball could be corroded in spots and could pass the test but once in service the rotation of the ball could cause a leak when the corrosion hits the seat.

The first plunger I checked leaked badly and led me down an unfortunate path of trying first to lap the seat with grinding compound and a lap fabricated on the lathe and polished to a taper. The ball was basically in good shape with no corrosion. The seat seemed to be in poor condition so next I tried cutting a new conical seat with an angle mill and lapping with tapers. Still no luck, and each round was cutting further into the plunger body risking unrepairable damage. Finally I cut down a 37 degree stainless flare fitting sleeve down and pressed it into the plunger body to create a new seat. At least with this I don’t keep cutting into the original metal. Out of the box this leaked some and I had to find a better way to lap the seats. I had tried internet searches looking for some sort of prefabricated conical or spherical ball hone at the start but found nothing. The original valve uses a 3/16” ball bearing and the seat was cut spherically. Finally three weeks into the disaster I found the right combination of keywords for the google search and found the answer – a company named Bal-Tec supplies copper balls encrusted with diamond grit specifically for lapping ball check valve seats – precisionballs.com. They come in 3, 6, and 9 micron grits, and “armor plated” which is 3 and 6 or 9 combined for longer life and pre-bonded on shafts. This did the trick for lapping the new seat and after many days labor, delays, and fussing I finally have the #1 sealing and ready for installation.

Meanwhile I have found that the whole process of checking the seat for leakage is more involved and when done thoroughly led to the conclusion that at least 14 out of 16 of my seats were actually good as is – actually better sealing than the two I ended up lapping. It could be if I had figured this out in the first place the first lifter might have been okay without touching it. Removing the 5/64” press fit wire dowel pin that keeps the ball in the plunger (with only ~.020” clearance) is a non-trivial matter, and “simply” pressing that pin out to lap the seat and replace the ball should be considered carefully before trying to “fix things that ain’t broken”. In my “series 1 ½” lifter, the pin must be ground flush to the taper of the plunger after installation or it will hang in the tappet body.

Doing the bubble test is meaningless if the lifter isn’t cleaned as well as feasible, whether it initially passes the test (from having thick oil still in the seat) or fails miserably from bits of contamination such as carbon particles.

I now have a procedure as follows for checking the ball seats: Pull the plunger cap off the top (it slides off, sometimes by hand or with gripping by pliers with protection from the jaws marking the surface). Flood the plunger body from the cap side with solvent such as WD-40 aerosol to flush the check valve. Clean the plunger body inside with swabs until they come out clean. Flood again and then blow through the cap end with compressed air and plugging the fill holes halfway down the plunger to force the air through the check valve past the ball. Follow by blowing air through the side holes at the tip. A buzzing sound means the ball is being vibrated and spinning on the seat – a little bit of this should be good to make sure the ball spins and gets thoroughly cleaned and changes where it sits on the seat. Now do the bubble test 2 or three times interspersed with solvent flooding and compressed air. Making the ball buzz a little bit assures multiple ball positions on the seat. I found after two or three rounds of this that plungers that were leaking now sealed when dry, and any further intervention was likely to provide negative improvement.

It will be months before I start the engine and start to know how successful this is, but for what it’s worth.

Jim

[Author nameAuthor names are only available to PAS members.]

A great write-up Jim, thank you.

Greg Long

[Author nameAuthor names are only available to PAS members.]

Well done! Remember there are no less than three different set ups from the era, then the later replacement Cadillac units. Also, the tappets should be center less ground when doing all this work. You can get them done local or Cislak sells them done on an exchange basis. Ed.

[Author nameAuthor names are only available to PAS members.]

Very good read-thanks James

John

[Author]

Posts