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MG MGA - Starter motor bolt

Hi all, the thread for the top bolt on my starter motor has stripped in the starter (the bolt is ok). I intend helicoiling it but, 2 questions - what thread is it likely to be (1960 MGA) and can I do it with the starter in situ.

It's also been suggested to me that it would be easier if just I drill it straight through, and put a nut and bolt in - any views?
Best wishes
D J Hill

That's interesting. My 2 spare starter motors are not threaded, just holes. The threaded part is the hole on the back plate.

Steve Gyles

The thread should be a 3/8 UNC and the bolt goes through starter and backplate and threads into the gearbox casing.

Should be possible to helicoil into the casing without removing the box.
Chris at Octarine Services

For the MGA, the starter bolts go through the mounting ear on the starter motor, then through the engine back plate,and then screw into tapped holes in the alloy bellhousing. When the threaded holes strip out it's time for a Heli-Coil.

The bolt is HBZ0613
Hex Bolt Zinc, 3/8-24-UNF x 1-5/8" long
NOTICE: Fine Threaded, info from the Service Parts List and Fastiner Decode Booklet

That changed to 53K149 -- 3/8-16-UNC x 1-5/8" long
Commencing with (C)117831 and continuing into MGB production 1962-1967. -- I know some vendors have it listed as 1-1/2" long, but I don't think the length changed when going from fine thread to coarse thread.
Barney Gaylord

When I fitted a 5-bearing engine onto my already installed 5-speed gearbox I discovered that all of the existing bell-housing bolts and starter motor bolts were actually nuts and bolts.
They had been in the car for over 10 years without any problem and so I simply used them all again.

That was around 4 years ago now and all still seems pretty secure (so far).
Because I installed the engine myself, I do check those bolts for tightness pretty regularly.

Colyn Firth

If the bell housing thread has been stripped, just drill or file it out a little and use a nut and bolt, as Colyn says. As long as the starter is firmly clamped in place it makes no difference. The nut and bolt is a bit of a pain to install and remove as space is quite tight to get a ring spanner on the top bolt.

For the lower threaded boss, this too can be drilled out and replaced with a bolt, it just needs the back of the boss attacking with a grinder to make it perpendicular to the hole so the nut can seat properly.

The long term secret is not to use the force of a gorilla to tighten every bolt!

Dominic Clancy

I thought it is the top gearbox hole that is blind and the bottom one is a through hole.

The easiest solution is the 3/8 UNC helicoil, the tap will cut the thread into the backplate hole on its way through to the ally casing but that doesn't matter.
Chris at Octarine Services

This thread was discussed between 27/06/2020 and 28/06/2020

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This thread is from the archive. The Live MG MGA BBS is active now.