Breather hole on Salisbury axle.

[Forumadmin]

Keith,
Another little point

Vic Boddy tells me the Salisbury differential's cover plate has a tiny breather hole in it, that can get blocked.

If blocked the interior can pressurise and push oil through the seals onto the rear brake shoes

A careful look on mine, and I can see no such hole

Do you know if there should be such a hole?

Edmund Nankivell

[Forumadmin]

Hi Ed,
There is one on each side to let grease out but I am not aware of one on the casing cover plate for oil . However, it would make sense.

Hence posted on forum to solicit other's views.

[Alf Heseltine]

Hi Ed, yes there is a breather hole on the Salisbury axle.
On the Javelin it is located, looking from the rear, about 2ins. from the joint of the r/h tube to the Diff. housing.
It is located just below the horizontal line on the r/h tube, allows the axle to breath.
If you can't see it then it may have been painted over in the past.

Alf.

[Forumadmin]

On the early axle it is about 1 cm from where the half shaft tube joins the diff casing, again on the right looking from the rear of the car.

[Alf Heseltine]

This might help.

Axle Breather Hole.jpg

Alf.

[Forumadmin]

Ed has found the hole, poked it out so another mystery solved.

We had the SA, SC and Jav on the road today. Jack took the SC to London and a mile from home on the way back he saw steam from the rad. The water pump pulley was no longer connected to the shaft. I went out in the Jav (now a service car) with a spare pulley and some water to get him home. A bit of work to be done there.

Also the Jav seemed to be slipping the clutch, so up on the lift with it to find all the Goodwood work had worn the clutch and it needed adjustment. Hopefully that is now solved, but will do a roadtest tomorrow. I tested it on the lift by engaging gear and driving the wheels and then applying the brakes. The clutch managed to overcome the brakes, so not much wrong there. But I was concerned that the brakes could not stop the wheels turning. So I put it in reverse (rather than first) to see if that made a difference (thinking it might be a leading/trailing shoe issue) but it did not. I will try the same thing with the Jup tomorrow as I would have thought there should be enough braking to overcome the torque of the engine. It may be there is just dust inside the drums causing loss of friction.

The SA had been given a modified new distributor yesterday as I had welded a bit onto the max advance stop as it was giving over 30deg rather than the desired 22deg. Still some work to do on the springs to get the curve correct as advance comes in too early. Assuming the previous problem is fixed, I plan to set up the programmable dizzie this week, and try to find the best curve in a roadtest with the computer controlling the curve.
This shows the slow speed (weaker) spring and the stop before welding. The gap was reduced to nearly half with weld.

20150404_170919 (360x640).jpg

This shows the high speed (stronger) spring which has a gap before it engages. That gap also needs to be reduced by bending the spring.

20150404_170944 (360x640).jpg

[Robin Fairservice]

I have a 1950 Javelin and have found the hole about 1 cm from the axle/diff casing join. The tiny hole was visible, but plugged with paint; so it is now clear. Thanks for solving a problem that I didn't know I had!

[BobCulver]

Nothing to do with breathers, but advance with uncertain distribitor innards and modern octane is a puzzle. An old motor mower control rigged as hand override advance can be more simple than electronic devices.

[Forumadmin]

Bob,
Good idea, the older type Jav distributor with external vacuum advance would make an easier starting point. I guess the later type with vacuum unit removed might also work. The main issue would be controlling the advance over the rev range whilst estimating the throttle/vacuum advance.

Obviously much easier on a dyno where you do not have to drive as well.
Out to test the clutch and brakes on the Jav now and see what else needs doing before its trip to Holland.

[David Kemp]

What stops crud/water from going in the hole? & oil escaping. My other old cars all have mushroom shaped breathers.

[Forumadmin]

The hole is small, it is pointing to the rear, there would be slight positive pressure most of the time, and oil should repel the water.
But if the axle was under muddy water for a long time, like wading through a flood, then there is a slight chance of ingress.

[NeilMoore]

Interesting subject. After 30 odd years of racing my Jupiter the spare tyre front was always covered with oil obviously from the small vent hole you have now discovered! Mine was not blocked with paint! A year ago we rebuilt the diff, it was tired, and addressed this leakage problem. My diff builder , Terry North , suggested a vent valve off a GM axle of some variety , they apparently all have them. So I blocked the small hole and re drilled for the vent valve to fit on the top of the side tube approx the middle. Now I can go sideways around corners at 6000rpm and the oil stays in the diff, and my spare stays clean! Actually I usually take the spare out when racing! Neil Moore