First (proper) engine rebuild - Morris Minor

[AceOfHearts]

Just started the engine rebuild on the spare engine for my girlfriends Morris. I got the engine very cheaply (£50) but it turned over freely and after stripping it down tonight looks in great condition inside. I have spent about 5 hours on the strip down tonight and have got it down to a bare block with just the camshaft and crank in place. Even all the timing gear looks brand new.

One question i have is that when installing the new rings, how should i prepare the bores (if at all)?

A friend of mine who has done quite a few engines just said new rings with no prep is fine and has had no trouble in the past, however my dad 'de-glazed' the bores on his boat engine with a strange contraption that attached to a drill

The bores look good inside with no lip and no scoring. What should i do?

No doubt plenty more questions in the near future

Edited by AceOfHearts on Thursday 1st December 22:23

[Tom777]

First take the crank and cam out before you cover them in swarf! You'll need to clean out the oil galleries and the best way to do this is to remove the brass plugs behind the front and back plate. Unfortunately you'll probably find big end wear but don't fret as a recon crank is about £75 exchange and shells are about £15 a set.

If there is a wear ridge at the top of the bore this will need to be removed by honing the bore, realistically if the step is of any significant depth you'll need to bore it. That strange contraption is a honing tool. It is used to finish the bore and leave a cross-hatch pattern which allows the rings to bed in and traps oil against the cylinder walls.

Don't forget to check the state of the oil pump while you're in there.

[AceOfHearts]

Thanks for that. The crank and camshaft are coming out tomorrow, i am completely stripping the block for dipping and pretty much everything is going to get renewed anyways. I am just using the out building for the strip down where the cleanliness is not that important. The rebuild will be done in the dining room where i can make sure everything is meticulously clean before going back in.

As i said the bores have no lip and the crank looks pristine. I will try and get some more pictures tomorrow.

[DVandrews]

If you dont plateau hone/glaze bust the bore, the new rings wont bed properly.

A flex-honer of appropriate size will prepare the bore correctly.

Dave

[Yuxi]

I dont think I would change the rings if there is no step in the bores, I had a 948 engine which had done about 80k miles with fairly large steps at the top of the bores which did not burn oil, it also did not knock so I didnt change any of the bearings. It did need a timing chain and tensioners, and half an inch of crap cleaning out of the oilpan.

[Tony427]

Yuxi said:

I dont think I would change the rings if there is no step in the bores, I had a 948 engine which had done about 80k miles with fairly large steps at the top of the bores which did not burn oil, it also did not knock so I didnt change any of the bearings. It did need a timing chain and tensioners, and half an inch of crap cleaning out of the oilpan.

Please change the plastic fuel filter for something more robust. You can get metal bodied filters for peanuts that do a proper job and yet won't crack and leak fuel, which then catches fire, all over your lovely pristine engine bay.

The plastic things are an accident waiting to happen.

Cheers,

Tony

[AceOfHearts]

I though it was good practice to replace the rings as a matter of course if the engine is apart?

[Steffan]

Worth remembering you are woring on arguable the best small engine ever made in Britain the A series.

The oil pump is critical above all else.

I would measure and micrometer everything up and only replace/regrind the items showing real wear.

As others said if the bores are not stepped or oval why rebore?

These are understressed engines not racing engines. Reasonable fit will work with the A series.

Cleanliness is next to godliness in engine rebuilds be scrupulous with swarf etc and clean out every oilway and surface very thoroughly.

Check the timing chain and the camshaft, pushrods and followers. Check the tappets there are several types the cast tappets are by far the best.

Whatever you do, run the engine in gently and change the oil and filter at 500 miles.

Saw an old 1953 A3o today engine in the car sounded lovely drove beautifully and has not been rebuilt in 40,00 miles.

Still going strong. That's the A series. Good Luck.

[Yuxi]

Tony427 said:

Please change the plastic fuel filter for something more robust. You can get metal bodied filters for peanuts that do a proper job and yet won't crack and leak fuel, which then catches fire, all over your lovely pristine engine bay.

The plastic things are an accident waiting to happen.

Cheers,

Tony

Plastic filters are OK in the right place, the car should really have had a metal pipe between the pump and carb.

I sold the car about 3 years ago. More dangerous was when I got the engine running, the float had a small hole in it so it filled with fuel, the carb overflowed and ran petrol all over the exhaust manifold, lots of white smoke but no fire!

[stevieturbo]

AceOfHearts said:

I though it was good practice to replace the rings as a matter of course if the engine is apart?

Rings should only be replaced if they need replaced IMO.

Or if any cylinder work is done, then they need replaced.

So it depends entirely on what condition the bores/rings are already in, and how far your rebuild actually goes.

If the bores were perfect and using no oil, then there isnt much need to replace them.

[Pumaracing]

Tom777 said:

If there is a wear ridge at the top of the bore this will need to be removed by honing the bore, realistically if the step is of any significant depth you'll need to bore it.

The second part I agree with but there is no point whatsoever in honing an entire bore out just to remove a wear ridge. All that does is make the unworn parts of the bore oversize just to match the worn bit at the very top which is only a tiny fraction of the bore length in the first place. You now have the whole bore as worn as the top half inch was and the piston will rattle around in there like a dick in a drainpipe.

The thing to do is remove the top step only i.e. the unworn bit above where the top ring runs to so the new rings can't break by hitting the step. This can be done with a ridge removal tool or if you're skilled you can blend the bottom edge of the ridge out by hand for a mm or so with a small stone in a Dremel or drill and then flash a hone over it to smooth things up.

You also used to be able to buy ridge dodger rings which had a step in the top ring but that were back inth' days when engines wore out a damn sight faster than they do now due to crappy oil and had to be rebuilt regularly.

With modern oils severe bore wear is almost a thing of the past. I've seen 100,000 mile VW Golf engines where all the original cross hatching was still visible. However I've also stripped down dozens of CVH engines where the bores were completely shagged. I think 7 thou wear over much of the bore length was the worst and it may well have been that Ford used a lower grade of cast iron compared to other manufacturers. Or maybe CVH owners just use crappy oil.