26 replies to this topic

[johnR]

All the crank and bigend bearings in my newly built 100 mile 1293 have been trashed, presumably by oil feed failure. The oil pump is a new Swiftune one which showed high pressure initially with a cooper ball type relief valve, then good pressure when I swapped back to the bullet type.

The cam bearings were starting to go as well. 

There seemed to be plenty of oil in the top of the engine (rockers,pushrods) etc.

Right from 1st use this engine' revs would crash with a clatter after about 3k revs, then recover after idling for a short while. I initially put this down to fuel starvation and spent much time and money upgrading this to no avail. Presumably, in the light of the failure, the bearings were partially seizing then freeing off.

I would welcome suggestions as to how to diagnose the problem. 

 

[Spider]

Before delving in too deep here, could you post up some pics of your Bearing Shells and the Crank ?

 

The Cam and Big End Bearings get their feed from the Crank Mains, so if there's no or poor flow to the Mains, the others will stave for Oil too, however, the Top End of the Engine, gets it's feed off the Front Cam Bearing, so this is sounding quite odd.

 

I'm wondering if the feed to the Front End was OK and it was the Middle and Rear Bearings that were Staving ?

If that's the case, I'd say there's a blockage in the Main Oil Gallery between the Inlet to this from the Oil Filter Head and the Center Main Outlet.

When disassembling Blocks for rebuild, regardless of what it is, I always pull the Oil Plugs on at least the Main Oil Gallery and poke a 8 mm rod through there (it's actually how I remove the 2nd plug). Then when I send the Block out for Chemical Cleaning, the muck that's in there won't end up trapped as they are flushing the Block at the end of this process.

Then, when cleaning the Block in my Workshop just prior to assembly, I have a small torch I put up to all Oil Galleries so I can look through them to be 100% sure they are all clean. Without inspecting in this way, I have no idea how clean they might be. To access and clean the Rear Main Bearing Feed, I also pull the Oil Pressure Relief Valve Seat, as that crosses that Oilway.

[Tones61]

Wrong main bearings fitted,or fitted wrong way around,i.e. Slotted one cap instead of block?

[Stevie W]

Sadly, I had the same thing happen to a Mini engine years ago.

 

The main bearings started rumbling after less than 10 miles and soon after the big ends started knocking. Like you there was initially plenty of oil pressure and plenty of oil all around the engine including around the valves.

 

When I stripped the engine, the main and big end shells were completely destroyed with embedded particles and the crank was scrap. This was due to a poorly cleaned block after machining work. I took it for granted that the engine builder had cleaned all the oil ways after the build....my stupid mistake!
 

My current engine was a kit from Minisport and this was I stripped as described above to ensure everything was spotlessly clean before dry building and measuring everything. The engine is still in my Mini now and has covered some 10,000 miles without any issues and is one of the smoothest running Mini engines I’ve heard.

 

Sorry for the lecture but I wanted to point out how important cleanliness is with a new machined engine and how I learnt the hard and expensive way. The particles in the shells turned out to be from machining of the bores and the oilways had not been cleaned out correctly. The oil filter was also full of metallic particles!

 

Hope you get it resolved and as Spider said, photos of the shells and crank journals will help in identifying the issue with your engine.

 

Cheers, Steve.

[whistler]

This lack of cleaning is not a new phenomena. I bought a brand new, in a wooden box, 1275 short motor from BMC back in 1970. Stripped it and found all sorts of crap in the oilways.

[johnR]

Before delving in too deep here, could you post up some pics of your Bearing Shells and the Crank ?

 

The Cam and Big End Bearings get their feed from the Crank Mains, so if there's no or poor flow to the Mains, the others will stave for Oil too, however, the Top End of the Engine, gets it's feed off the Front Cam Bearing, so this is sounding quite odd.

 

I'm wondering if the feed to the Front End was OK and it was the Middle and Rear Bearings that were Staving ?

If that's the case, I'd say there's a blockage in the Main Oil Gallery between the Inlet to this from the Oil Filter Head and the Center Main Outlet.

When disassembling Blocks for rebuild, regardless of what it is, I always pull the Oil Plugs on at least the Main Oil Gallery and poke a 8 mm rod through there (it's actually how I remove the 2nd plug). Then when I send the Block out for Chemical Cleaning, the muck that's in there won't end up trapped as they are flushing the Block at the end of this process.

Then, when cleaning the Block in my Workshop just prior to assembly, I have a small torch I put up to all Oil Galleries so I can look through them to be 100% sure they are all clean. Without inspecting in this way, I have no idea how clean they might be. To access and clean the Rear Main Bearing Feed, I also pull the Oil Pressure Relief Valve Seat, as that crosses that Oilway.

I've had a bit more of a look at the damage - bore honing polished away but no scoring, pistons very light scoring - hope they'll be OK. The big ends seem to have suffered the worst, followed by crank shells.

I've poked a wire through the crank oil holes - seem clean - I'll remove the block oilway core plugs next.

[johnR]

I've now removed the oilway plugs - the galleries are clean. I've checked the oil pick-up as best I can, which appears fine. The oil pump cover has  a little swirling from the rotor but low oil pressure didn't seem to be a problem until the final journey when the gauge dipped as the rumble intensified. it appears there is no obvious problem which doesn't help me at all. In good news, whilst rooting around for the old cam to compare it with the new one I found a spare crank which I'd forgotten came with the second block I bought when we couldn't use the original one because it was linered.

I'm going to take the bits back to the company that did the machining tomorrow to see if they can spot anything I've missed. 

[GraemeC]

That's nasty!
The fact the mains have only really gone in the centres will no doubt provide clues (to someone who understands much more than me - Oz, Spider....)

[Stevie W]

Hi John,

Those are exactly as my bearings looked and crank journals and that does seem to be contaminated oil.

My oil pressure dropped over a couple of miles followed by main bearing rumble.

 

From your photos I think I can see dirt embedded in the shells.

 

Cheers, Steve.

Edited by Stevie W, 01 March 2021 - 05:57 PM.

[Spider]

Thanks for the Photos.

 

It looks like there was some Oil in there, but not much more than a dribble.

 

If the wrong sized shells were fitted, the engine would be locked up right from the word go, so I doubt that as a cause / issue here.

Was the Crank Re-ground for this build and was it checked for sizing ? It looks to me like it may have been re-ground but still ever so slightly over-size particularly on the Big Ends.

Also, there can be issues when bolting up Oil Pumps to the Block. The drillings / threads in the Block aren't too deep and it's easy to fit the Bolts, tighten them up, but they have bottomed out in the Threads just before pulling the Pump down hard, though usually this results in the Oil Pump not being able to draw up any oil from the sump, but, not always.

I'd also check that the Oil Pressure Relief Valve is seating fully. If that's jammed open at low engine revs, most of the Oil will be getting dumped back in to the Sump.

 

When I rebuild Engines, I go about it with a mindset that everything is 'wrong', then check everything to be proven otherwise or find issues before they become that. So, early on, that means a lot of measuring.

At a later point in the Assembly, pretty much before the Head and Gearbox go on, I'll check the Oil Pump by inverting the Engine in the Stand, putting some Oil in to the Suction Side drilling in the Block and Turning the Engine over until I see the Oil coming out in to the Oil Filter Head, then fit the Oil Filter, top up the Oil in the Suction drilling and keep going until I see it coming out of the Mains, Big Ends and Cam Bearings and at least look around the Oil Pump for any leaks there, although as it's not making any pressure, it doesn't tell me much - but hey - at least I looked ! It's sadly not a complete test at this point, but at least satisfies me to a point that fundamentally, I should get Oil Flow when fully assembled and in the Car.

 

[MiniMadRacer]

The above makes a lot of sense and is a very useful "tip", I have only ever fileld the oil pump with oil and the filter but your method is much more thorough... I am learning a lot today... never to oold to learn how not to destroy a new engine build.....

 

Off topic I wonder if it would be uiseful to have a "biggest mistakes" section... I have mixed up centre mains thrusts and instead of putting in STD / STD and 30"/30" I put them in STD/ "30" and STD /"30" when in a huirry... needless to say it threw the thrusts out after very few miles and destroyed the crank and block... I only ever made that mistake once... and at least it was back in the day when blocks were cheap and plentiful

[Tones61]

Before delving in too deep here, could you post up some pics of your Bearing Shells and the Crank ? The Cam and Big End Bearings get their feed from the Crank Mains, so if there's no or poor flow to the Mains, the others will stave for Oil too, however, the Top End of the Engine, gets it's feed off the Front Cam Bearing, so this is sounding quite odd. I'm wondering if the feed to the Front End was OK and it was the Middle and Rear Bearings that were Staving ?If that's the case, I'd say there's a blockage in the Main Oil Gallery between the Inlet to this from the Oil Filter Head and the Center Main Outlet.When disassembling Blocks for rebuild, regardless of what it is, I always pull the Oil Plugs on at least the Main Oil Gallery and poke a 8 mm rod through there (it's actually how I remove the 2nd plug). Then when I send the Block out for Chemical Cleaning, the muck that's in there won't end up trapped as they are flushing the Block at the end of this process.Then, when cleaning the Block in my Workshop just prior to assembly, I have a small torch I put up to all Oil Galleries so I can look through them to be 100% sure they are all clean. Without inspecting in this way, I have no idea how clean they might be. To access and clean the Rear Main Bearing Feed, I also pull the Oil Pressure Relief Valve Seat, as that crosses that Oilway.

I've had a bit more of a look at the damage - bore honing polished away but no scoring, pistons very light scoring - hope they'll be OK. The big ends seem to have suffered the worst, followed by crank shells.I've poked a wire through the crank oil holes - seem clean - I'll remove the block oilway core plugs next.

Look like bearings wrong in mains,i.e. The ones with holes in should be in the block to allow the oil through,
Prob why it's eaten itself

[johnR]

 

 

Before delving in too deep here, could you post up some pics of your Bearing Shells and the Crank ? The Cam and Big End Bearings get their feed from the Crank Mains, so if there's no or poor flow to the Mains, the others will stave for Oil too, however, the Top End of the Engine, gets it's feed off the Front Cam Bearing, so this is sounding quite odd. I'm wondering if the feed to the Front End was OK and it was the Middle and Rear Bearings that were Staving ?If that's the case, I'd say there's a blockage in the Main Oil Gallery between the Inlet to this from the Oil Filter Head and the Center Main Outlet.When disassembling Blocks for rebuild, regardless of what it is, I always pull the Oil Plugs on at least the Main Oil Gallery and poke a 8 mm rod through there (it's actually how I remove the 2nd plug). Then when I send the Block out for Chemical Cleaning, the muck that's in there won't end up trapped as they are flushing the Block at the end of this process.Then, when cleaning the Block in my Workshop just prior to assembly, I have a small torch I put up to all Oil Galleries so I can look through them to be 100% sure they are all clean. Without inspecting in this way, I have no idea how clean they might be. To access and clean the Rear Main Bearing Feed, I also pull the Oil Pressure Relief Valve Seat, as that crosses that Oilway.

I've had a bit more of a look at the damage - bore honing polished away but no scoring, pistons very light scoring - hope they'll be OK. The big ends seem to have suffered the worst, followed by crank shells.I've poked a wire through the crank oil holes - seem clean - I'll remove the block oilway core plugs next.

Look like bearings wrong in mains,i.e. The ones with holes in should be in the block to allow the oil through,
Prob why it's eaten itself

 

They all had holes in and I made sure the holes lined up perfectly with the oil galleries with some light dressing with a file.

Edited by johnR, 01 March 2021 - 07:48 PM.

[MiniMadRacer]

How did the shells line up with the holes in the block... I have seen some line up poorly and have relieved the block hole to line up with the shells on abused race lumps

[Spider]

Off topic I wonder if it would be uiseful to have a "biggest mistakes" section.

 

A 'Trophy' thread in PQT I think would be a great idea. Not just for us to show off our Trophies, but also one that others can learn from. On making stuff ups, finding them and sorting them, I've found I have learned 100 times more about that aspect of the vehicle than if it all went 'smooth'. The 'issue' though I see with it from a learning aspect is as it would cover so many different areas, it wouldn't be helpful to try to look things up in it. When I guess you look at it, the PQT thread is one long such 'thread' that is better for searching through, however a stand alone Trophy thread might be good for a giggle.