Trim/Lift Valve Body re-assembly

Greetings all,

I've recently acquired a boat with a circa 1975-76 Chrysler 75HP....it's going to need some work, but currently trying to reassemble the tilt/trim valve body/pump that was included "loose" in a bag. One of the ports had the threads stripped out and I was able to repair that.

This is the style of valve body that contains clips in the sides (I believe the original Prestolite style). On this particular style, there is no adjustable pressure setting...they appear fixed. However, the two springs included are of different stiffness and I'm looking for guidance on which side of the valve body should use the stiffer of the 2 springs.


Image courtesy RRitt rebuild listing.

Thanks for any help,

-JeffR

Re: Trim/Lift Valve Body re-assembly

short stiff spring goes closest to the tiny small spring. slightly longer and less stiff spring goes away from the tiny spring with the ball bearing on top of it. shims vary from vb to vb and serve dual purpose of protecting aluminum spring tower and making small adjustments to pressure.

Re: Trim/Lift Valve Body re-assembly

Thanks so much for the clarification RRitt...much appreciated.

I had a 50/50 chance of getting it right and testing it, but this confirms it for me. There is only one shim (same thickness) on the top of each spring and so that should be OK.

As one of the port's threads was stripped out, I was able to re-drill and tap to 1/8 NPT to get a fitting installed. However, because there is restricted space and I have limited access to various fittings, I was going to cut off the flare from the tubing and simply use a compression fitting. I'm hoping this will hold up with the pressure that the pump will deliver. Do you have any suggestions for this?

Thanks again!

-JeffR

Re: Trim/Lift Valve Body re-assembly

don't cut tube. bend a dog leg so that nut is till straight. drill out hole in vb leaving 1/8" thickness in bottom. flush and wash thoroughly. there is recess behind regulator seat where debris can collect. need to remove and flush out any metal flakes.

cut brass adapter to match hole depth. wash hole and fitting with acetone, lacquer thinner, or similar for 100% oil removal. use pipe compound or JBalumaweld on threads to lock adapter into hole.

cutting corners or doing things the easy way does not usually work out with hydraulics. you have such small parts with such small tolerances under such high pressures that they will seek out and expose any imperfection.

Re: Trim/Lift Valve Body re-assembly

Thanks RRitt,

Yup, I've already got the VB drilled & tapped to 1/8" NPT with a brass fitting trimmed back to tighten in the shallow hole. I haven't permanently installed it yet.

The problem is finding an 1/8" NPT to flare adapter that will fit the original flare on the tubing. I can easily find 3/16" compression fittings that could accommodate the steel tubing.

On the Chrysler motor set up, all but one of the tubes is already bent with a dogleg to clear the motor mount. I'm not sure if there will be clearance for any additional fittings to stack up in sequence before the tube interferes with the motor mount.

The port that is damaged is "C" in the installation diagram (connects to the bottom of the lift cylinder).

Is there a particular fitting part # that you're aware of that fits this? When you do a re-drill/tap of a bad port, what thread form do you typically use? I had no problem getting 1/8"NPT to fit within the material around the original port.

-JeffR

Re: Trim/Lift Valve Body re-assembly

I don't think compression fittings are good for the 2000 or so PSI that the pump can deliver. I do remember reading somewhere that you can NOT use compression fittings on the brake system of automobiles and I suppose that they run about the same PSI

Re: Trim/Lift Valve Body re-assembly

Working with aluminum, there is no way to snug them down tight enough to withstand those kinds of pressures. I'm splitting brass nuts on compression fittings, trying to stop water leaks in household plumbing with 80# of pressure.

Re: Trim/Lift Valve Body re-assembly

Here's a photo of the re-worked port, re-tapped to 1/8NPT with progressively shorter taps to accommodate a full depth thread in the shallow blind hole. The brass fitting is shortened back slightly as well to ensure tightening on the tapered thread prior to bottoming out in the hole.




Sounds like I'll have to try to find an 1/8" NPT to Flare fitting adapter to use the tube "as is" rather than cutting it to use a compression fitting. Considering the proximity of the pump/valve body to the motor mount, I might need to install a 90 degree fitting pointing down and re-bend the tube or re-flare the tube to fit in place.

Thanks for the help!

-JeffR

Re: Trim/Lift Valve Body re-assembly

Perhaps you can try a "banjo" fitting and hose as used on automobile calipers. Just another idea.

Personally, I would just buy another pump body from RRitt!----WAY easier and less time consuming.

Re: Trim/Lift Valve Body re-assembly

1/8 mpt to 3/16 brake tube is a standard fitting in stock at most auto parts stores. drill the aluminum deeper using a standard drill bit leaving 1/8" thickness (didn't I already say this?) .... and use a flat bottom tap. If required buy two taps and use a dremel to cut one to make a flat bottom hole. Cutting corners or using substitute parts does not play well with hydraulics (didn't i already say that too?).

Re: Trim/Lift Valve Body re-assembly

Hi RRitt,

Yes, I think I have that completed....check the photos. I just need to track down the proper fitting to install rather than the compression fitting that I was gauging the hole with.

-JeffR

Re: Trim/Lift Valve Body re-assembly

brass fitting from NAPA for 1/8 pipe to brake tubing.

shorten up the brass fitting to same length as hole. Get some quickset JBweld. apply one drop to aluminum internal threads on VB. not too much because excess may plug up hole in bottom. Coat external threads on adapter. when assembled the JBweld should form a seal about 1/8" high around the base of adapter ... which has been machined to same depth as hole. JBweld is rated at something like 3500psi so this will serve dual purpose of sealing your threads and preventing the adapter from working loose with age.