Bolt/Screw size

[Angelo]

Can anyone tell me the size of the 4 bolts at the front of the oil pump on a 1951 16M engine please. I understand they are BA but not sure if 2BA or 3BA
Thanks in advance.

[dave16mct]

They are 3BA, screws at the front, bolts at the back.
Dave

[Andy51]

I may be wrong here, but I seem to recall that the 3BA bolts are specials with 4BA size heads? Andy

[Angelo]

That's what I understood - anyone know where I might get a 3BA helicoil kit from?
Thanks

[Pharisee]

The bolts have a shouldered hex head (I can't tell you the hex size). If the engine is still in the frame, you can't get a screwdriver in easily, hence the hex head on the return side of the pump.
If the engine is out of the frame... don't be tempted to use screws instead of the hex head bolts. If you need to take that plate off at any time in the future, you'll probably have to take the engine out of the frame again to get the screws out.

(It's an old photo and the fibre washer under the pump location pin cap has since been removed.)

18S_2292.JPG

[cbranni]

Hello Angelo,

I have never seen 3BA helicoils for sale only 2BA, but you could tap the 3BA holes out to 2BA or even M5 and use screws to suit, you would of course have to open the holes in the plate to suit.

Colin

[Pharisee]

Hello Angelo,

I have never seen 3BA helicoils for sale only 2BA, but you could tap the 3BA holes out to 2BA or even M5 and use screws to suit, you would of course have to open the holes in the plate to suit.

Colin

3BA helicoils are certainly available but not cheap if you have to buy the kit. One of the oil pump plate threads in my engine was helicoiled by a guy who specialized in vintage engine repairs. If I remember correctly, 3BA threads are also quite common on Lucas electrical stuff.

https://www.sdtsengineering.co.uk/produ ... r-kit-3ba/

https://www.ebay.co.uk/itm/Helicoil-thr ... Sw1m9arWRt

[cbranni]

Sorry for the false information, I stand corrected.

Colin

[Groily]

See also https://uni-thread.com/tr_ba_inserts.php
Tracy Tools, for once, don't seem to stock BA kits.

Quite a bit of 3BA on leccy bits, yes.
Notably, HT pick-up securing screws of various sorts, and the thread on the Lucas and BTH contact breaker centre screw.
But most of them are not really standard screws, as the screw-on pick-ups for K2Fs need a hex (as well as the slot), and all the centre screws are one-offs with slightly domed hex heads on many, or hex + slot on face-cam mags. There are also lots of safety spark gap screws (all with pointy ends) at 3BA too.
So it's quite a common size in fact, along with 2 & 4, and also a fair bit of 5 come to think of it.

[Angelo]

Yes I had seen the 3BA helicoil sets - very expensive for me to do one thread!