#4 big end running?

[kiwichief]

Hi all from NZ.
Our 1962 4 door had a recent repower with an 1100 from an early Sprite. It appeared in good condition throughout so we put a new set of shells, a set of rings and some head work (hard seats etc). 80 miles of driving and #4 big end ran. Polished crank, a good clean out and new shells and drove about 100 miles and #4 ran again. Sent to engine reconditioned, acid bath, all galleries cleaned, new set of shells, new oil pump, swapped out oil pressure valve for 9/16 ball bearing, fitted oil pressure gauge, temp gauge and tried again. Oil pressure and temp never faulted through the whole failure, 180 miles and same result. I'm very much over it. It has every one stumped down under (to date) I'm thinking boat anchor or land fill and on the hunt for another block? Has anyone had a similar experience that they can shed some light and maybe save the old girl from the scrap yard? I love working on our Morrie but it would be nice to drive it on occasion and not end up under tow or on a trailer.

Cheers Kiwi Chief

[MarkyB]

Have you check the crank for ovality? Micrometer job.

[JOWETTJAVELIN]

Were all oil ways thoroughly cleaned through the crank etc with a piece of wire?? A bath on its own is not sufficient.

[Ratbag]

If the crank measures OK I'd go with looking at big end bearing clearances using plastigauge between bearing and journal, if necessary refacing the caps & reboring the big end (prob easier to get new conrods!). Could also be bearing quality?

Phil.

[bmcecosse]

Either there is no oil reaching #4 from the main bearing - so as above , the crank should be probed with a length of wire/rod, or perhaps the con-rod is bent ? Are the shells tight in the conrod? Any chance they could have spun round at some point and damaged the rod end? Was the crank reground? 'Polishing will not be enough after a bearing has 'run'.

[kennatt]

I would think that any engine re conner would have had the shaft checked especially after a run bearing.If the shaft is ok and the oilways are clear then it could be the con rod,the big end can get knocked out of round which prevents the shells from seating , B Series engines were prone to this but not A series ,so,As BM says, after a run bearing its about essential to have the shaft reground and oversized shells fitted,and even more so now that it has run so many times,the journal can't possibly be still within tolerances. I certainly would never put a shaft back in after a run bearing, without a regind. Just not worth the risk.and after so many ,I would also replace that con rod as well it's bound to be damaged by now

[les]

In the past I have used a syringe full of petrol to check oilways are clear, as I would say lack of lubrication would be the only cause. If you 'jet' the crankshaft oilways with a syringe you will be able to see if number 4 journal has the petrol exiting from it's oil hole. You might find it doesn't. Although now I've said all that, no oil present would, I'd have thought, left a very discoloured journal to give you a clue and your post doesn't indicate such.

[bmcecosse]

The oil flow may just be 'restricted' - by some debris in the oilway.......

[JOWETTJAVELIN]

Which is why it needs poking out. Bearings don't keep running for no reason - clearly there is some blockage along the line.

[MarkyB]

Have you got any pictures of the knackered bearings?

[kiwichief]

Thanks all for your replies. The last trip to the recon man, all bearings were plastiguaged, another con rod replaced the old one as the bearing had spun in the end of the rod and all galleries had wire put through as well as the acid bath. It’s a bit hard to tell when the parts all go away and you don't get to get a good look yourself and how well they were checked. Considering they did a freebie and won't be wanting it to come back again they should have done everything in their power to get it right. I will be having a lot more to do with the checking of parts myself this time if I re build it. No photos of the last failure but the motor is still in the car from this effort. Petrol and syringeis not a bad idea, worth a try. I will get a photo and post when I get it out this time. Great there is a keen group out there willing to help. Bit of a grin ah. I will keep you posted. Cheers Kiwichief.

[kiwichief]

Thanks all for your replies. The last trip to the recon man, all bearings were plastiguaged, another con rod replaced the old one as the bearing had spun in the end of the rod and all galleries had wire put through as well as the acid bath. It’s a bit hard to tell when the parts all go away and you don't get to get a good look yourself and how well they were checked. Considering they did a freebie and won't be wanting it to come back again they should have done everything in their power to get it right. I will be having a lot more to do with the checking of parts myself this time if I re build it. No photos of the last failure but the motor is still in the car from this effort. Petrol and syringeis not a bad idea, worth a try. I will get a photo and post when I get it out this time. Great there is a keen group out there willing to help. Bit of a grin ah. I will keep you posted. Cheers Kiwichief.

[kiwichief]

Problem found!!!!
The plastic surgeons and a sagging bodies best friend, but no so for A series engines. Silicon!!! One small drop to many in the mix sent a piece into the main front to rear oil gallery, partially lodging its self in # 3 main oil feed allowing enough oil through to feed the main but at causal moment not enough oil for # 4 big end The cleaning and feeding through of wire only moved it slightly for it to lodge back in the hole once the oil pressure came up to 60psi again. I can stop thinking of the next implant as I am now happy to replace the same motor in its old body with no more modifications. It has nice curves without adding to them at the moment.
Cheers All

[JOWETTJAVELIN]

Excellent news! Thanks for the update.

[MarkyB]

Well done! I bet the acid didn't even mark silicone.
A blast from an airline might have shifted it I suppose.

[bmcecosse]

Why was silicone anywhere near the engine in the first place?

[les]

It's sold for assembly purposes apparently, although without the corrosive qualities of bathroom silicone. Personally I prefer the more conventional stuff but too much of any compound would have the ability to block an oil passage and presumably that was the case here.

[bmcecosse]

Why would anyone use it? BMC didn't... So why do it now? AVOID!

[MarkyB]

Lots people use it as insurance or to bodge up ripped paper gaskets.
Not recommended but very common before they became classics.

How it got into the crank is an interesting question though, did someone use it to seal up the oil pump perhaps?

[les]

Why would anyone use it? BMC didn't... So why do it now? AVOID!

Well bmc may not have used it but their agents did. I well remember my local leyland dealer saying to me that their workshop now use it as they were suffering too many oil leaks from customers cars, and this stuff was sorting it. I used some at the time, when rebuilding an Allegro engine and must admit it was oil tight. The blue hymol (?) just feels more 'sticky' so I'm still using that.