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MG Midget and Sprite Technical - 1500 Bottom End rebuild with Engine in the car

I have decided as the weather is shocking to bite the bullet and rebuild the bottom end of my car. Only doing this as I have been getting 140 on a compression check across the 4 pistons when it should be 160 so I am going to deglaze and fit new piston rings. Bores are all excellent with no notable lip to them.

I have removed number 1 piston and below is a pic of the bearing surface which to my untrained eye seems ok? Crank has be reground and bearing is .010 US am I ok simply buying new bearings and replacing these when I rebuild?

My plan is as follows:

1)Remove all the pistons.
(KEEPING THEM IN CORRECT ORDER ECT)

2) De glaze cylinders

3) Wash everything down

4) Change main bearings and thrust on the crank ( Read this can be achieved in the car?

5) Refit pistons and new bearings?

5) Send head off to have hardened valve seats and new guides.

Does this all seem logical or would people do it differently ie pull the engine?

C Carter

Either pull the engine and do it all properly or leave it alone.
Chris at Octarine Services

"Either pull the engine and do it all properly or leave it alone." --- Didn't you see this comment Chris? --- "I have removed number 1 piston and below is a pic of the bearing surface"

My experience of the 1500 engine is in a couple of Triumph saloons, TC manual and auto. The ends went on both of them. If that pic was of an A series engine shell, I'd use new shells and know I'd get away with it.

But on the triumph engine, that uniform line on the shell would make me take a very close look at the crank. A number of people on here have remarked at how they've changed the shells regularly on 1500s, almost as a service item.

If it were me, for a little extra work, I agree with part of Chris's answer. Pull the engine and grind the crank, and if the bores are good, new rings.
Lawrence Slater

I checked the crank and it has no marks on it. But appreciate what you are saying about pulling the engine and doing it properly. I dont mind pulling the engine just boils down to one thing cost of getting all the work done!
C Carter

Yes I saw it - but my comment stands - either put it back together ( the marks on the bearing are typical dirt in the oil marks ) if oil pressure is OK and the engine is running I would not be worried about 140 psi (if indeed the gauge is accurate). Glaze busting & new rings would unlikely improve the pressure much because the piston grooves will still be worn.

Spending money on doing part of the job is nearly always false economy - I'd just save up until I could afford to rebuild the engine fully.
Chris at Octarine Services

did you do a wet pressure test as this can show if rings are wearing . always thought it was more about even pressures rather than how high they are 140psi don't seem to low mine are 160psi on a recon'd engine
mark 1500 nearly on the road

Yes did a wet test and it went up to 155 across all 4 not a dramatic increase. But it does seem to be burning a bit of oil. I wanted to know the condition of the bearings as its a 1500 and they are prone to excessive wear. For now then I think I will simply replace the conrod bearings on all 4 and get the car through another year whilst saving for a rebuild.
C Carter

I would suggest taking a look at no. 2 and 3 big ends before making a final judgement. If I understand correctly they are both fed by the centre main oil way. 1 and 4 are fed by their own feed, 2 and 3 share. Therefore wear is more likely to occur on 2 or 3. I have read, but don't know the reasoning why, that apparently no. 3 big end is normally the one to go bang out of the four.

Malcolm.
Malcolm Le Chevalier

You can do this in the car. But like Chris says, and I agree, you will not improve your engine much doing what you list. I did mine in car because the shells were well down and I had oil leaks and needed an inspection and clean out. (I at last listened to a good 1500 and almost fainted at how bad my bearing and end noises were) I also need an engine running right now to use the car as its my occasional day car (about 4 times a week sometimes more).
Mine now runs better because the shells were so bad (a lot lot worse than yours).
Having grovelled to do it this time to get by I will be doing my next one out of the car (on the spare engine that turns over luverly) over the winter, where I can see everything and lay things out easily, and then swapping them over, and the clutch, all at the same time.
By then I will have the kit to swap the engines and I know I will do a better job a lot easier on an engine out of the car.

While you can even do a 100hp plus upgrade with it in the car I would still only do it when out. Even if you don't have a proper stand and have to make one.
Dave Squire

I have read that too Malcolm will have a look at them tonight, I did read though that the conrod bearings wear more so fingers crossed the main bearings will be ok, but for piece of mind I will check.
C Carter

Yes Chris that's what I did.
Dave Squire

Don't just use your eye to check the crank journals. At least magnify, and see if there's a mark to match the line in the shell. As I said, on an A series engine, I wouldn't worry, but on the 1500, as Malcolm just remarked there's an oil feed issue and they can wear prematurely.

I'm all for saving time, so if all really looks well, don't pull the engine. But actually it's not really much extra effort to pull the engine, and then far easier to work on it when it's out of the car. Much easier than lying on your back under the engine.
Lawrence Slater

I have a pit in my garage so its quite easy working on it sat on my stool. I couldnt see any marks that match the shell but will look closer tonight under my magnifying glass. I have read when replacing the mains on the 1500 you can do it in the car but risk scratching the crank when removing and replacing them? If that is the case I will just pull the engine anyway.
C Carter

It depends what your expectations are. Pulling the engine and "doing it all properly" will take some weeks, cost several hundred pounds and set you up for the next 50,000miles. Doing what you propose would be in the some tens of pounds and give you an ok engine for maybe 10,000 miles, or maybe 30,000 miles. It's more of a gamble but may be worth it.

Is the line showing on that bearing a ridge or a groove? Being on the line of the oil feed hole it may be an unworn ridge of white metal and rather less serious than it looks. The important thing to check is that the crank is polished smooth. There should be NO detectable ridges in it as you run a finger nail across the surface. Do as Malcolm says and check all 4 big ends. If they all pass this test, then personally l would go against all the other advice offered so far and reassemble with new bearing shells. But then I am the one Lawrence referred to who used to do this job as a 25,000 mile service item when bearing shells were only £10 a set.
Guy W

Thanks Guy, I will check the big ends, If I can make the engine run another 10,000 miles I would be more than happy at that then rebuild when more funds are available.
C Carter

I should add, Chris @ Octarine is a professional with a lot of experience who no doubt does a quality job for his customers - and advises accordingly. I make my own decisions, right or wrong, and live by the results, and blame no one else.

Maybe the best idea is to do the cheap job on this one for now, but aquire a spare engine to work on and rebuild to a good standard for the future. As Dave plans to do.
Guy W

Well...

Considering you already have the bearings out...aka a photo of the bearing,

Id go ahead and replace all 3 bearing sets...I doulbt it would be very expensive

Connecting rod, main,and the thrust...and new nuts for the con and main as well ...with 140 psi, and new bearings id think you can get several 10s xxx of miles out of it before having to do a proper rebuild

If the engine wasnt already apart, then id have left it alone

This is one of those... "I am already there, so I might as well...." moments

Prop
Prop and the Blackhole Midget

Having rebuilt my engine twice in the past 2 years, i never considered doing a bottom end rebuild in situ - Getting it out of the car is a 2 hour job for a novice or a 30 min job if you've done it a few times. Whack it on a stand (£40) and your life is so much easier from now on... if you are planning on cleaning it, you will be much safer to do that out of the car. I think it will be a false economy not to pull it. - - Someone on here will have a hoist you can borrow I'm sure.

I think people are wrong to suggest it will cost hundreds more - the extra costs are, rad fluid... maybe some new hoses? (if you can't borrow them then you'll need a hoist and a stand).
C L Carter

I would put a rebuild (as opposed to just renewing the bearing shells) at several hundred because if I were doing that I would get the crank ground and also balanced together with the (lightened) flywheel. The 1500 in particular benefits from having the crank balanced and it doesn't add that much more than a simple crank grind job. But costs do mount up pretty quickly once you start to have parts machined or replaced. By comparison, new shells and a gasket set are cheap!
Guy W

This thread was discussed between 03/10/2013 and 04/10/2013

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