Series III Crankcase Oil Gallery Plugs

[Mike Allfrey]

I am replacing the crankcase involved in the coolant leakage saga with a Series III case set that I have held for some time. The problem is that the brass oil gallery plugs (four off) are missing. These are, as far as I am aware, not listed in the spare parts catalogue that covers Series III, and they replace Part Number 50625 (the earlier aluminium taper plugs).

Does anyone know if these brass plugs are available from JCS?

If not, can someone advise what the thread for the brass plugs is? I have tried numerous thread taps and bolts and the only fit I have found is standard 10 mm, a loose fit which I sort of doubt. My thoughts are that the threads in the crankcase are a pipe thread, for which I do not have a thread tap for.

The brass plug is like a machine screw which seats against its head diameter, not tapered like the earlier aluminium were.

Any help/advice will be greatly appreciated.

Regards,

Mike A.

[PJGD]

Mike,
Looking at the original JCL crankcase drawing [available in the Technical folder on this site] which is very difficult to decipher, it states: 2 Oil Galleries Counterbored 9/16" Dia. x ⅛" Deep & Tapped 7/16" BSF to Depth Shown at Both Ends as Shown. See image below:

Oil Gallery Plug Feature.png

[David Kemp]

Checking my series 3 engine I can confirm they ate 7/16 BSF.
The gearbox studs are a perfect match.

[Mike Allfrey]

Thank you for the information. I will try a 7/16-in. BSF stud to check the thread again. Also, we will be applying heat to each plug, allow to cool and then locally heat the crankcase; once well warmed, will use an impact screwdriver to dislodge the plugs in the scrap crankcase.

In the past, I have never found these gallery plugs to be so tight. They are single centre punch locked, which means that Loctite would not have been used. We learn all the time!

Thanks,

Mike A.

[Mike Allfrey]

Update:

The four plugs are out of the scrap crankcase set. The technique used was to locally heat the plug area with a propane gas torch, and once warmed through, used an impact screwdriver (purchased on E-bay). Using the largest flat bit, that fitted the slot snugly, a few hammer blows got them started and a normal screwdriver completed the task.

The crankcase set is scrap because it is cracked, oil feed pipes chiseled off for some reason and the lower coolant jacket walls are corroded. It is a Jowett Engineering reconditioned crankcase set, not a Series III.

Job done!

[Mike Allfrey]

Update:

The Series III crankcase is back from machining for separate rear main bearing thrusts. I have found that the spot facings are a much larger diameter that that for the plugs extracted from the scrap crankcase. No centre punch indentation is going to secure the brass plugs. Am considering the use of Loctite 680 to secure them.

Trial fitted the crankshaft and found snug 0.0015-in. end float - perfect, a win at last!

Mike A.