Pressure testing JD engine

[DanM]

Hi guys- I'm wondering the results you have of pressure testing a JD? I can't stop the soap bubbling at the intake housing nut area. Thing I don't get tho is the housing is not a sealed fit on its OD into the cylinder. So, any pressure from the intake manifold seems to be able to go "around" the housing, and out past the nut. It is not related to the valve open or closed. Even if the threads of the nut have sealant, the pressure can get over the top of the housing, past the rocker tower base and out. I made the top of the intake housing as flat and smooth as I could, I did the same on the rocker tower bottom and the surface the nut rides on, and I checked the bottom of the nut for flat- I did this using 220 or 320 on a granite plate. I lapped the bottom of the housing to the cylinder.

I don't have any leaks at the intake manifold nuts, etc. But this still seems to be a source of a vacuum leak in operation. But the design to me does not seem to lend itself to being sealed? At least not like a Pan I did where it was obvious at a manifold o ring. When that was fixed, it made sense.

Any thoughts?

[Jerry Wieland]

Dan I was really hoping someone with a little experience with JD's would have an answer here. I am building one and I can just imagine that I would have the same types of problems.

Jerry

[Robert Luland]

There was a resent thread on the jd yahoo site on this. Bob L

http://autos.groups.yahoo.com/group/harleyjd/

[DanM]

THx Bob.

Last night, I took it all apart and did what I had been refusing to do- I used black hi temp silicone gasket maker around the top of the intake housing and the bore it fits in, like a fillet, and a thin film where the rocker towers seats. then i put it back together with Rectorseal #5 on the nut threads and the top surface of the rocker tower base. Tonite, after 24 hr to cure I will pressure test again!

A lot of other discussion is about the sealing lip at the bottom of the housing. But i seem to be worried about the top area or the clearance between the housing and its bore.

[sswaney]

Dan
I used Plumbago. Powdered graphite and motor oil mixed well for the inlets and inlet nuts. This stuff is described somewhere in the J Model literature but I can't tell you where I read it exactly. May have been in the Shop Dopes collection sold by the Motor Company. Or I might have seen it in Motorcycle Repair for the Motorcycle Repairman. I will see if I can locate the exact
source but it may take a few days.

Scott

[Robert Luland]

Dan, Keep in mind that the clean thing is all that works. Wipe down every surface that you are appling goop to with lacquer thinner (any thing else will leave a film) with a white rag and repeat until the rag stays white. Goop doesn’t stick to petroleum. Bob L

[DanM]

THX Bob- I used acetone- hope it works as well.

Well, the results are------NO soap bubbles! I know that there has been no heat and vibration to act on the seal, but I'm going to move forward and run it this way.

By the way guys- when I pressure tested my tanks I actually BALLOONED them. I had used about 10-15 psi. A guy I know told me 2 psi max for tanks. I actually had to reform the section of the inner wall on the right tank where it needs to fit through the frame- it literally would not fit into the frame all the way!!! I had to hammer back in the concave sections!!!!! Abnd they were PAINTED!! So far, they did not leak and all is well there too, but I could not believe it could happen.

[T. Cotten]

.....By the way guys- when I pressure tested my tanks I actually BALLOONED them. I had used about 10-15 psi. A guy I know told me 2 psi max for tanks. I actually had to reform the section of the inner wall on the right tank where it needs to fit through the frame- it literally would not fit into the frame all the way!!! I had to hammer back in the concave sections!!!!! Abnd they were PAINTED!! So far, they did not leak and all is well there too, but I could not believe it could happen....

Dan!

Next time, just cork the tanks up and immerse them in hot water.
The heat expansion will produce enough pressure to display leaks safely.

....Cotten