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MG Midget and Sprite Technical - 1275 Spigot Bush
Just rebuilding my 1275. It is a 12V engine from a 1972 midget GAN5 RWA.
The gearbox has been overhauled and the rebuilder (Peter Cavanagh) recomended fitting a new spigot bush. He gave me a bush and told me it is oilite and they wear. BTW he has done a first class job.
The shop that rebuilt the short engine (CMA Chester) told me that the bush is phosphor bronze and never needs replacing. Nevertheless they confirmed it was a bush and not a needle roller bearing and removed it for me.
Now then I have since read that the 12V engine should have a needle roller bearing and not a simple bush. The moss catalogue quotes two different bushes, 1A1559 (
|I don't think it's too critical, and they last yonks.|
If the original in the crank was oilite, and you have a replacement, I'd put that in. The roller bearing is an improvement I guess, but as the oilites last so long, if you wan't to save money I'd use the oilite.
But I wonder if the roller bearing type controls the 1st motion shaft better, and helps the ribcase box last longer?
|The bush and needle roller are not interchangeable.|
The needle roller needs a much bigger hole in the crank.
It looks like you have an early crank...maybe even EN40, but probably not.
|Ah, I stand corrected. :)|
|Lee. I remember,as I was there with you at Peter's workshop, what he said about the spigot bush or pilot bearing being a factor in the longevity of the 'box and I think Dave has solved your problem in as much as if the one Peter gave you is a good fit, that's the one to put in. It would be nice if you did have an EN40 crank.|
|Oilite bush it is then!|
Now for the dumb questions: I did not pay attention to the end of the crank when I took the engine out and the engine shop removed the old bush. I am assuming the bush fits snuggly right into the furthest recess. From the face of he flange that fits to the flywheel there is a first level recess then a smaller recess further in. The oilite bush seems to be about the right size for this furthest recess. I tried pushing it in with my thumb and it would not go so I'm guessing this is the place but it needs knocking in with a hammer. It has been soaked in oil.
Bernie ~ I need to get cracking or it looks like Maddy and I will be on your aniversary run in Sonia's Figaro!
Dave ~ you now have me spending lunchtime googling what the heck an E40 crank is! Shame I have now fitted the sump so I can't inspect the crank further. Not got the flywheel on yet so I might look to see if there are any casting marks on the output end.
Oh and I have just realised that fitting the flywheel before the sump would probablly be the better idea! Shall have to torque it up while holding the flywheel with something wedged through the teeth and the starter hole. D'Oh.
I'm quite enjoying this rebuild but have to sneak the hours in when Sonia is not around, she wants me decorating the loft!
It would have been better to have the shop fit the new bearing as well as removing the old one. You really want a spigoted stepped drift to tap it into place and a guide sleeve to make sure it goes in square as they are easy things to damage. The drift and guide sleeve are easy things to make if you have access to a lathe. I would question the shops statement about the oilite bush not wearing, maybe they haven't dealt with many. They do wear and go dry with time and they'll wear more if the clutch is ridden but then the carbon release bearing would likely go first and a good time to check and replace the spigot bearing is when the clutch is being done.
EN40 is the material used for the crank and was used on early 1275 cranks and they're sought after. IIRC no point looking at the output and of the crank as the EN40 mark is on one of the webs between the front or rear pair of main bearings.
|sorry if I'm attempting to teach people how to suck eggs here but don't forget to leave the new bush soaking in oil for at least 24 hours before fitting. I have a spsre which has been soaking it up for about ayear now - just in case...|
|Don't worry too much about having and EN40 crank unless you are going racing. The rest of the 1275s were Tuftrided, until 1974. But for the '74 engines they dropped that too.|
The interesting thing is that there doesn't seem to be any kind of a durability difference between the cranks in the '74s and the rest of the 1275s, so perhaps the tuftriding was not needed, either, after all?
Oh, by the way, the oilite bushing is also found in the '74 crank, so that wouldn't be evidence of an EN40 crank.
If I remember Horler, he said that the EN40s were only used for a few months in '67, and that there are not good records to know for sure just when it was dropped.
|The oilite bush is in. I fashioned a make shift step drift from a big bolt, couple of nuts locked on and some insulation tape around the tread. Knocked it in easy with soft mallet. Flywheel is on. Should have clutch and gearbox on tonight.|
This thread was discussed between 28/02/2012 and 01/03/2012
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.