For the chevron seals on the main ram, the seals are preloaded independently of the rubber packings. The ram stop ring is threaded and is designed with 4 pin holes in the face used to tighten the stop ring against the chevron packings. After they are loaded, the packing rings can be installed and loaded independently using the packing nut.
Apparently, Blackhawk used to have a specialty tool to use for torquing the ram stop ring. In a pinch, it could be done with a narrow punch or two in the pin holes. The difficulty with this approach is the preload on the chevron seals is not very repeatable and there is a higher potential to slip causing the punch to contact the surface of the main ram. To remedy this, I made a face spanner using some 1/8” rods and an old section of pipe split and bent to the appropriate size. I added a nut to the top of the tool so I could use a torque wrench to set the preload, allowing me to have a number to adjust from if it did not work properly after reassembling.
Here is a picture of the bore where you can see one of the pin holes on the ram stop ring for the face spanner.
Here is the custom spanner, its not a looker, but it worked well.
Initially I torqued the chevron seals down to 70 in*lbs. All appeared to work fine on the jack, but while load testing, the ram slowly lowered. I opened the top cover on the reservoir and could see oil flowing from the ram over travel port from the front of the jack to the rear, which indicated oil as bypassing the main ram chevron seals.
I took the hydraulic unit back off the jack, pulled all of the main ram rubber packings and tightened the ram stop ring to 100 in*lbs this time. The ram still was able to be pushed in by hand, but with slightly more drag than the initial assembly. With 100 in*lbs, the jack held firm for the 2 hours that I tested it without dropping at all. I do not know if this is the proper tightness, but it appears to be working and is not terribly hard to adjust later if it needs to be further tightened.
Overall Thoughts
After finishing the functional portion of the rebuild, here are my thoughts. I do have a good functioning jack, but this work has to be a labor of love. Between the cost involved in the rebuild kit and the time required, most people would be better off getting a newer jack. I enjoyed this project though and learned quite a few things.
Thanks to help from this forum and others who have rebuilt jacks, such as Steve Bryant whose thread can be found here with advice from Willy-C and Highball.
https://www.garagejournal.com/forum/showthread.php?t=101909&highlight=blackhawk+steve
Here is a quote from Steves Thread by Willy-C that I used as my guide.
"strip all pistons, packing nuts, retainers, valve plugs.....leave the adjustable overload cartridge together but remove it to expose the valves....
Scrub, flush base with solvent cleaner or carb spray....use carb spray with nozzle to reach inside the ports where valve ball reside.....one thing that I remember about the valve seats is the 7/32 suction valve ball seat can be worn too deep......hopefully you won't run into that......
Do not mix up valve balls and 2 stage trip spring/poppet
Polish everything that moves or drags on moving parts (glands, sleeves ect)....
Inside the pump chamber in the back there is a stud that can be removed with an allen wrench......I used to remove it for polishing (bore too) and use the same part to adjust the tension on the small v packings inside the pump piston when you start putting it back together.....
When you start to put everything back together you should be on clean table/rags.....clean tools, clean grease AND CLEAN HANDS..!!....then blow out completely with compressed air
Soak the packings in oil (some folks do it overnight)....use clean grease sparingly on the v packings......
Best to install valves, 2 speed poppet, overload valve (DON'T OVERTORQUE IT) first (in case you have to blow it out with air)
preload the v packing set inside the pump piston using the stud that was removed inside the pump chamber.....the stack height of all these v packing sets are very sensitive so be careful to put back the same amount of v packings......there should be a healthy drag on the v packing set but not too tight......
when installing the v packings in the pump chamber and ram chamber put them in loose and tighten them up with the plungers installed (not too tight) with a healthy drag using a small punch (don't marr the piston surfaces), then the pump and ram packings can be installed afterwards (one at a time), then the packing nuts......
The overload may not need to come apart cuz you can visually see if it's not holding a load when testing.....If needed then you can pull it after the whole jack is together if it leaks by......
I'm sure I missed something, the others can chime in if so.....
It has been a while since I've done one but the principle is the same as any jack, they all have there strange tricks.....
Most of the blunders I've seen was the V packings not in right, too loose, too tight, not the right height, twisted in place......well you get the picture
Hope this helps....
Willy-C...."
In addition to the advice from above, I would add in the following.
- Insert all of the rubber packings very slowly and work in small steps incrementally around the circumference of the seal. It is easy to get the seals to “capsize”, but difficult to pull them back out. I ended up ruining one that did “capsize” while removing it, but fortunately the kit came with a spare.
- Be sure everything is ready for assembly prior to putting any of the chevron seals in. They fit quite tightly and depending on the orientation of the lips would be nearly impossible to remove without damaging.
- If you want to rebuild an older jack like this, be prepared for the project to take a while, especially if there are unknown issues, such as the galled threads I found on the HP piston packing nut.
