WillieB's 1275 Engine Rebuild

[MiniDave]

WillieB has decided to entrust his 1275 engine to me for a rebuild, he did a fantastic job crating it up for the trip from Atlanta to KC, and it arrived yesterday.

I uncrated it and got it set up for the tear down. I pulled the head off first, and since it's already had quite a bit of work done to it including some port work and hardened seats, it will take very little new work - just a clean up and a refresh of the three angle valve job.

The carbon buildup on the pistons was pretty much what I expected for a 30K mile engine, so I set about tearing it down.

The complaints are that it has an unidentified "rattle", has blowby and has started smoking and has a couple minor oil leaks.

[MiniDave]

Once the head was off I got busy with the rest of the stripdown today.

The front cover came off, revealing a single row timing chain with tensioner. Chain looks OK but we'll replace it as a consumable.

Then the back end - I noticed quite a bit of play in the pivot pin for the clutch arm and when I got the disc out the springs were loose - maybe the rattle? We'll see. He also indicated the clutch wasn't releasing correctly so we'll address the play and replace the disc. Everything inside the clutch housing was clean and dry.

Once I got the engine split from the gearbox I noticed that the center oil pickup tube had no screen on it? Hmmm....that's not right. I haven't found the screen or any parts of it, but there was some brass swarf around the oil pressure plunger. We'll replace those parts too, along with the oil pump, fuel pump and water pump, just for good measure.

I loaded the block up on the bench and marked the rod bearing caps, then pulled them and the mains and removed the crank. Crank looks very good, records indicate it's been turned 10 thou under on both rods and mains and the rotating assembly balanced.

The bores didn't look bad, there was no ridge at the top and I haven't yet determined if it's been bored oversize, but it looks like it might be 40 over right now based on the size of the land between the cylinders.

Once the crank came out I got a surprise......the mains and thrust washers had little wear on them, but the upper bearing in the rods were a real surprise for an engine with approx 30K use. I'll let the pictures do the explaining.

So, I'll mic the crank, pistons and mains and then take the crank, rods and block off to the machine shop Monday morning where we'll give them a more precise measurement and make plans accordingly. In the meantime I'll get parts ordered and hopefully everything will arrive back about the same time.

[MiniDave]

The cam looked good but a few of the lifters were worn, I'll leave it up to Willie B if we go with a new cam or just replace the lifters. This head also has the sintered rocker arms, I'll suggest we go with the 1.13 Cooper S rockers if I can find them and of course a new rocker shaft as those are definitely a consumable.

Here's a pic of the inside of the gearbox, the center oil pickup is the tube in the top of the pic - there should be a screen on it much like the second pic. If it got chewed up by the gears and sent thru the oil system it seems I would be finding bits of it, but maybe not.

WilieB if you still have the oil filter cut it open and see what you find in it, OK?

The bores looked clean with no ridge at the tops - which is usually a good indication -  but the engine was blowing oil smoke and making a bit of crankcase blowby.....so I anticipated worn rings - they didn't look bad but the ring gaps on the few I checked were pretty large, a good indication of worn rings. I'll have the machine shop check for taper and wear in the bores, and if it's in tolerance we'll just give it a light hone and put some new rings in.

We'll mic the crank carefully and see if we can figure out why the upper rod bearings are worn like this - I've never seen them wear only one of the shells like this, but it makes sense that they'll wear the tops more than the bottom shells as that's where all the thrust is taken. Mains and thrusts looked as new.

[BruceK]

Brad, I'm curious. What oil was used in the engine?  And what was the change interval? 

[Willie_B]

Brad, I'm curious. What oil was used in the engine?  And what was the change interval?

Always been using good oil. Since just after the engine was built I have been using this oil. Change intervals close to 2000 miles. 
https://www.schaefferoil.com/vtwin-oil.html

[MiniDave]

JASO MA2 is what Richard recommends too - especially for automatics. He also thinks it's better off with 10W40 rather than 20W50. He did a paper on it and I think it's a sticky here someplace.

I've run nothing but 20W50 in my engines too.

The engine was really clean inside, and other than the weird bearing wear and ring wear it was clean as a pin inside. Three lifters had wear pits in them, the rest looked good and the cam looks good too.

[94touring]

What cam is in there?

[BruceK]

Brad, I'm curious. What oil was used in the engine?  And what was the change interval?

Always been using good oil. Since just after the engine was built I have been using this oil. Change intervals close to 2000 miles. 
https://www.schaefferoil.com/vtwin-oil.html

Interesting.  With the Mini's shared engine/gearbox/diff that motorcycle oil makes a lot of sense.   Thanks.

[Willie_B]

What cam is in there?

https://www.calverst.com/webshop/engine/bp255-%E2%80%93-camshaft-hi-torque/

[Jimini II]

With a missing oil screen and the fact that a Mini engine uses the gearbox as a sump i am surprised the engine has not failed already and looks as good as it does.
The rod bearing wear on the upper shells is very strange, this engine will need some serious measuring before going back together.

[cstudep]

I agree that it needs some serious measuring before going back together. Generally speaking when the overlay is worn through like that it's either a lack of oil or a clearance issue. Since it's only worn on one side of each bearing and it's somewhat symmetrical in that the outer area is worn on the outside bearings and the inside is worn on the inside bearings I would be looking for some sort of clearance issue.

On another note, I saw somewhere in one of your threads Dave that you used a machine shop that is "north" of you some distance. Would you be willing to share what machine shop that is? It would be nice to know where one is somewhat close by that knows these engines I have a couple of 1275 blocks that came with my car that I ought to do something with one of these days. On one the guy removed all the caps without marking them so it would probably need to be line bored.

[MiniDave]

Sure, for that sort of work - cranks and line boring -  I used a place called Claycomo Engine Rebuilders. Joe is the crankshaft expert - I never used them for any block work tho, just cranks. Part of the reason is they're so freaking busy that it takes 2 or 3 months or more just to get a crank done. But he does amazingly good crank work. I don't know if they can bore or line bore and engine this small.....I never asked them. They also do balance work if you take all the rotating parts with you they can balance the lot.

The place I used to use up north for block work has gone out of business, so I was using a place just a few miles from my house in Lenexa - QCKC - but they can't line bore a block with bearings that small. In fact, a 1275 is the smallest block they can bore the cylinders in (I had to take a 998 elsewhere) but they can do that and surface the top of the blocks too. But, they can't do cylinder heads for me as  they don't have small enough arbors to mount the cutters in the valve guides so - I send all the heads down to Nolans, who have been in business almost as long as I've been alive. Nolans also have the newest and most modern head machines.

The guy I used to use in Lenexa has moved to a shop in Lees Summit, so I'll be taking Brad's block and crank over to him - he is a consumate expert and really knows his stuff, so he'll look at it with me. His first observation was that maybe the rods were on the wrong pistons - as these rods are offset - that's a possibility. This shop can do the crank and the block work, so now I'm back to using one shop for heads and only one for the rest of the engine. I'll see how they do before recommending them, but I have a lot of faith in the guy that I know there - he's done several blocks for me already, including the one in the Innocenti.

I would have used him for cylinder heads too if he had the correct arbors, his current shop can't do them either, but Nolans can and they do excellent work.

I'm sure there are plenty of engine shops in your area, the problem is their equipment isn't sized for these tiny engines.

[pbraun]

I bet  the bearing wear would indicate crank slightly out of balance.  Just a guess. Symetrical pattern 1 and 4 on outside, 2 & 3 inside.

[MiniDave]

There are plenty of indications that the rotating assembly was balanced, whether it was done right or not I won't know till we decide what we're going to do to rebuild it - for example, whether we'll go back with new pistons or re-use these - and I have them rebalance it.

But first things first, need to find out if the crank is straight and whether the journals are tapered. Also need to see if we can get away with simply honing the cylinders or if it will need to be bored.

Lastly - I need to see if I can find any of the remains of the screen from the center oil pickup.

Of course the block will be thoroughly cleaned out - including removing the plugs in the oil galleries.

[MiniDave]

So, further info....

I cleaned the head up and pulled the valves out - the guides look fine, valves will only need a slight touch up and they'll be good too so the head will need very little work to get it sorted. I will replace the rocker shaft and if WillieB agrees replace the standard sintered rocker arms with Cooper S forged 1.13 rockers.

On closer inspection the cam has damage on three or four lobes too, so we'll be getting another cam and a new set of lifters.

I also found one of the pistons had a chunk of ring land broken out and being held in by the rings, so we'll be getting new piston(s) depending on whether it needs to be bored out or not.

Once the machine shop checks out the crank carefully, then we'll know what we're doing there too - I'll also have them check the rods for straightness - although it seems to me if the rods were bent it would wear on the cap end bearing too opposite the wear on the top bearing. So, not too sure what's going on there yet.

There was damage to the rear cam bearing too, tho not as bad as on some engines I've seen.

Lastly, tomorrow I'll remove the lay shaft and take out that oil pickup tube and see if I can find the remains of the screen that's supposed to be there.

[cstudep]

Thanks for the info on the machine shops Dave, unfortunately there are only a few up around here that I know and would trust and like you said they do not have the equipment to work on this small of an engine. It would be great if the new place works out since they can "do it all" as you say. Sending a head out for work is a lot easier than the engine block, and KC is close enough for a drive down to not bother me much. Not sure when I might tear into one of these engines but it's good to have a place to call on when the time comes.

Seems like machine shop work is a dying art in most places, which is unfortunate. A custom fab shop/machine shop is one thing I think I would really enjoy doing, but the equipment outlay is extensive for sure. Maybe it will be my retirement job some day LOL

[94touring]

What compression ratio was he running?  Good time to bump it up to 10:1 and toss in a 266 equivalent cam to really wake things up.

[Willie_B]

This engine started as a MG Metro so it was already 10-1. May be a touch higher from surfacing the head and black last time around. Or it may have balanced out due to the pistons being 20 over.

[94touring]

If you guys get all the specs I can plug it in the calculator.

Edit:  If you started with a STD 1275 metro at 10:1:1 and went 20 over to a 1293cc it gives you 10:23:1.  30 over 1301cc would give you 10:29:1 and 40 over 1310cc would give you 10:36:1. 

[Jimini II]

Quite a lot of damage for a relatively low mileage 30k engine, also strange when you consider that a good quality oil has been used with regular 3k miles oil changes.
It will be interesting to see what the machine shop comes up with regarding the crankshaft and connecting rods.

[PoolGuy]

Hi all. I joined to keep an eye on tmsmini's fuel injection project, but always interested to see what people find when they strip an engine.

The wear pattern on the big end bearing is very interesting, almost as if someone had managed to fit the rods with the offset 180 deg out, look forward to hearing the actual reason though.

As pointed out by someone else, there's a lot of damage on a relatively low mileage engine.

[BruceK]

Hey PoolGuy.  Welcome to Restoration Mini!

[tmsmini]

Hi all. I joined to keep an eye on tmsmini's fuel injection project, but always interested to see what people find when they strip an engine.

I better get off my ass then...I wish I had the energy of Dave.

[MiniDave]

All the parts went off to the machine shop this morning, they were having an electrical panel replaced so the power was off - and it was DARK in there!

I got them all the specs so they can measure everything out, and - good news - they can do my cylinder heads too, so I don't have to run all over town dropping parts here and there.

Power is supposed to be back on this afternoon - they'll drop the crank in the jig and put a dial indicator on it to see if it's straight and check the journals for taper, then we'll know if it's OK or needs a grind. At the very least we'll micro polish the journals.

If the cylinders aren't tapered we may be able to just hone them, then we decided since one piston broke we'll replace the set rather than take a chance that the others don't have hidden cracks somewhere.....of course I won't know what size to order till they check it out.

The consensus I'm getting is that the bearing damage may have been due to detonation, and that's the rattle he was hearing and mistaking for some other sound. Still speculation right now but that's the load side of the bearing and the load side of the rod.....still investigating as we want to be sure before we put it together again.

I sent the pic off to Kent Prather at Prather Racing to see what he thinks, I probably won't hear back from him till this evening tho as he has no cell phone service in his shop.

Things are moving along.

[94touring]

The piston land did give me the impression of detonation.  Easy enough to do on a higher compression motor.  That's why I'm so big on installing widebands.