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MG MGA - Bore honing

Just read a post by L Christiansen about an engine rework he did ..incl.honing the bores. I was looking up how and see there are a variety of tools and techniques ( incl. whole diameter brushes ) and would welcome any comments and recommendations as I will be embarking on such in a month or starting to pull together the kit and a file for the work.
Neil Ferguson

just read the comprehensive write up on Barneys site so now well briefed on gadgets needed...
Neil Ferguson

Neil, I honed the bores with the block sitting in the car.
It was quite a challange to keep the honing sludge away from the main bearings, so I made some plugs of rubber foam that could sit about 1/2" up in the bore from below.
After honing the bores I removed the plugs and finally did just a few strokes in the lower part.
This seems to have kept the mains free from the nasty stuff.
As stated by Barney: clean everything VERY carefully!
Good luck.
L. Christiansen


With all the engine work building up have you considered going the full hog for long term satisfaction and having a rebore? There are companies in the UK who offer a mobile reboring service with the engine in situ. I presume the same exists in Australia. If it was me I would whip the engine out rather than lying under the car to do all the piston removal etc. However, I am guessing that removing all the Judson stuff will be quite a pain?

Steve Gyles

L Christiansen ....plug idea is a good one..will do. What tools did you use for the edge,bore measurements, honing etc.. ? Need to gather such in preparation . are probably right ..but have done it once before in situ in another life (50 yrs ago on a spitfire ) ... And have my hoist and fully working arms so will take the plunge . Keeps me out of the pub...
Neil Ferguson

I agree with Steve. It is a relativly easy job with the engine on the bench, especially the cleaning process. However it is absolutely possible in situ too.
For the measurements I used a 2 point micrometer.
You have to measure the bores right under the top ridge and in the bottom where the rings stops. Any difference defines the taper of the bore. Then you have to maesure the out of round at each top and bottom point. If any of these measures exceed the specs. In the manual, you should consider a rebore and new pistons.
For the honing I used the 3 leged thing with 180 grid stones.
Finished with a slight plateau honing with 500 grid emerald paper.
The above mentioned grids have given excelent oil control.
Don't forget to gap the new piston rings.

L. Christiansen

Back in the late 50's early 60's my Dad had a '54 Vette. He needed it bored so someone came out and did it in the car in his garage. Always wondered how it had been done,it's hard to imagine. Until you guy's brought it up I had no idea that it was still done. Here in the states I have never heard of anyone else doing it.
gary starr


Here is an example:

Steve Gyles

Interesting Steve. I googled it and could not find anyone here in the states that does it. It would sure save me some work on a future tractor rebuild. Just for grins I include a pic of said car. While not a MG it must have provided the spark for me and sport cars.

gary starr

This thread was discussed between 28/03/2016 and 30/03/2016

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