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MG MG Y Type - Banjo bolt oil feed at rear of block

I am a regular contributor to the MGA BBS, but am a first time visitor here in the Y section.

I have today been refitting the cylinder head on an otherwise almost totally original never restored and rust-free MG YB. We took the head off and sent it to Peter Burgess because the valve guides were shot and the engine was smoking in spite of having great compression.

The refit went totally as planned with one hiccough - the banjo bolt at the rear of the block by the Jackall reservoir wouldn't screw in. I have tried a BSP die on it and it doesn't fit. The part is number 141 at this link

http://www.moss-europe.co.uk/shop-by-model/mg/t-type/engine/engines-components/external-engine-4a5794.html

I completely trust Peter to have correctly restored the head, so am suspecting that the banjo bolt (a curious round-headed thing with a pair of flats) is not original.

I believe the banjo thread should be 1/8-28 BSP and the length should be 1". Am I correct? Can I use a hex-headed banjo from a TD/TF or are there differences in the cylinder heads?

And should the ribber sealing ring between the two halves of the induction manifold have anything to hold it in place?

If there is interest I can take photos of the car when I go back to finish the job with a correct banjo bolt. All that is left to do is fit that and adjust the valves.
Dominic Clancy

The bolt and the fitting are sealed by two soft copper washers, not by the threads, so it is not likely that it is BSP. (Normal) BSP has a tapered thread. There is however a straight thread BSP (BSSP I think.)

More than likely its either metric or BSF.
Most of the engine fasteners were metric.
Just measure the diameter of the thread as a start.

Hold a metal 6" scale next to it and count the threads and measure the total distance of the threads.
figure what part of an Inch the distance is or how many mm the distance is, and from that calculate the TPI or Pitch.

Again I doubt BSP.

Jim B.

JA Benjamin

Oh yes, I forgot, be sure to replace the copper sealing washers. They need to be soft.
You could try to anneal by heating them red hot and letting the cool but new ones are the safest bet.

Jim B.
JA Benjamin

this is a picture of my banjo bolt. The way you describe yours sounds correct.

Willem van der Veer

The way you describe your banjo bolt and the picture that Willem posted is the same as all those I have on my engines. I will see if I can check the thread for you.
Keith D Herkes

Hi Dominic, my banjo bolt is the type will two flats as willems picture and copper washers to make the seals, Graham
Graham Sharpe

I have now found a couple of sources that quote the same 1/8-28 BSP dimension and a also Moss part number for TD/TF.

From Dave DuBois, who is usually very reliable
http://www.mgexp.com/article/xpag-xpeg-fasteners.html (penultimate item in the table)

And also the Y-Type register who should be expected to get this right!
http://www.mgccyregister.co.uk/technical-information/miscellaneous/threads/

The banjo bolt we have doesn't measure up to the BPC spec, so I have mailed PB to see what he can suggest / confirm before buying a new correct bolt. The bolt I have measures .378" on the threads. .361" in the thread, and 17mm on the flats.

Incidentally the one we have is chromed brass - is that standard or another indication that it has been replaced at some time?
Dominic Clancy

Hi Dominic,

The round bolt with two flats is for the rear of the head (not block) on TCs .... I think the same for Ys but not 100% sure. I am pretty sure they are metric with 1mm thread pitch (very fine). I can't go in to the shed to check as I am babysitting! Might be able to get to that later.

Bob Schapel
R L Schapel

Sorry Dominic,

I was wrong. You are correct. It is definitely 1/8" BSPF 28. That is what it says on a Sutton tap which goes perfectly into a spare head in my shed. A round/two-flatted banjo bolt fits the same head perfectly. I knew I had a tap to suit because I had to tap a thread in a brass insert I made to repair the oil supply hole in a Laystall head for my TC race car 22 years ago! (I now remember my 10mm x 1.0mm taps were for tapping 10mm spark plug holes.)

The bolt length is 1" but less than half is threaded ... including the threadless waisted bit.

Beware a common cause for leakage from these banjo bolts. They have a step on them and so can run out of thread before they seal on the washers. The washers need to be quite thick (or you can counter-bore the hole a bit). The original washers were hollow copper with soft filling ... asbestos?

Bob Schapel
R L Schapel

The same TC bolt fits a Wolseley 4/44 head, which has the same casting/long-reach plugs as TD/TF (although the smaller Y/TC valve size). A Wolseley banjo bolt (hex like TD/TF) fits a TC head. I just tried both in my shed. So yes, you can use a TD/TF bolt.

I don't know a lot about threads but assume the F in BSPF means "fine" and is different from ordinary BSP. My 1/8" BSPF tap is not tapered.

My sample (2-flat bolt) is about 18mm across the two flats and 20mm on the full diameter. It is chromed steel. (Attracted by a magnet)

Sorry, I can't answer the induction manifold question.

Bob
R L Schapel

This thread was discussed between 10/12/2016 and 13/12/2016

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