Spun A Big End Bearing

[skinner2k3 3]

I spun a big end at combe on saturday.

 

Whipped the sump off last night and found the big end on number 3 to have spun in the rod.

 

The pin is actually unmarked so I am considering cleaning everything up and putting a new set of bearings in.

 

Taking a micrometer home from work tonight to measure up.

 

I know this isnt the ideal solution but compared to pulling the engine out, dropping the gearbox, removing the crank, regrinding, etc etc I am willing to risk the £30 and couple of hours work just putting bearings in.

 

What I wanted to check was if the rods need re-machinging after spinning a bearing?

 

Regards

 

Ben

[Tom Fenton 1,542]

Yes the rod needs to come out and be resized, plus really you need to strip it to clear all the bearing debris from the rest of the engine. If you don't do this then really you are just throwing good money away as your new bearings will last about 5 min.

[Cameron 16]

What he said.. it's false economy no matter how little you spend.

[skinner2k3 3]

Oh arse!

 

The rod still had its original honing marks on so I assumed it would be ok.

 

Quick question on bearing deris, I drained the oil into a clean container so I could check for any metalic bits and its clean. The bearings are also in one piece.

[Miles 331 1 Cars]

Try it and see, It may last 2 mins or 2 years you never know, If the rod shows no sign's of heat damage then you do stand a chance.

But really it should all be stripped cleaned, checked as even good std rods can be out of round

[sub205 5]

Try it and see, It may last 2 mins or 2 years you never know, If the rod shows no sign's of heat damage then you do stand a chance.

But really it should all be stripped cleaned, checked as even good std rods can be out of round

the particles flow from the failed bearing to the sump, from there the oil pump sucks it in and pushes it trought the filter.

in the theory there should be no garbage in the oil-flow, but at some point the filter is full and the bypass valve opens.

 

at least dismantle the oil pump and clean it, also the feed from there to the filter. the filter too, of course.

[skinner2k3 3]

Even if it were only 2 minutes for the £30 I will spend on bearings I am willing to give it a go. I really do feel that it could work as the engine was shut off so soon and because of the lack of any real visable damage to the crank pin, rod bore and shells.

 

If it doesnt work, I am not too proud to tell everyone and its lesson learned.

 

Yes, I will deffinately be stripping and cleaning out the pump and everything else I can. Also have access to a very cheap supply of 15-40 oil and will be running a couple of sumps full through as a flush before added good stuff.

 

Place your bets now

[sub205 5]

Even if it were only 2 minutes for the £30 I will spend on bearings I am willing to give it a go. I really do feel that it could work as the engine was shut off so soon and because of the lack of any real visable damage to the crank pin, rod bore and shells.

 

If it doesnt work, I am not too proud to tell everyone and its lesson learned.

 

Yes, I will deffinately be stripping and cleaning out the pump and everything else I can. Also have access to a very cheap supply of 15-40 oil and will be running a couple of sumps full through as a flush before added good stuff.

 

Place your bets now

i think it will work. Its not the best way, but after a flush and cleaning all parts, there will not be any noticable particles in the engine anymore. check the head! take off the cover and look for debris. they will ruin your cam. if there are some, you should clean the whole engine, of course!

[grandos 16]

My bet is around 10 miles of driving before it decides to start knocking on the door.

 

I tried this exact same idea for the cost of a set of bearings, with no notable damage to be seen, measured with a micrometer and used plasti-gauge aswell but it still failed again.

 

In the same position I'd probably try it again for a quick fix as its only £30 and a bit of your own time. Worse case it needs a strip down, best case it works a treat.

[Beastie 1]

Gut feeling is with Tom Fenton on this- I wouldn't even think about it without dropping the cap and boring or delapina honing the parent bore of the rod to size.... unless desparation calls in which case.... check the nip on a new pair of shells in the rod: Tighten a pair of new shells in the clean parent bore and then slacken the big end bolts. Turn up the rod bolts with fingers until they touch the cap and then tighten one side only carefully until the butt faces are just lightly "nipped" together. Next measure the gap on the other side of the rod between the butt faces with a feeler gauge. The absolute minimum gap is 3 thou. If you have at least this then you are likely to get away with it!

[skinner2k3 3]

I am still not sure what to do with it, its the risk of it going again but taking something else out with it.

 

Thanks Beastie, thats good info. I would not have known to do that.

[skinner2k3 3]

All bets are off, I am changing the engine.

 

Measured the crank journals last night and found the one which spun to be oval by 0.09mm.

 

Thanks for all the advice anyway chaps. Best crack on.

[Cameron 16]

Is that out of tolerance?

 

Edit: Yes! Haynes says max journal out of round is 0.007mm!

Edited June 17, 2010 by Cameron

[welshpug 1,657]

0.007 is the tolerance stated in haynes, so certainly well out of tolerance.

 

1st regrind is typically +0.3mm.

[Anthony 1,003]

Measured the crank journals last night and found the one which spun to be oval by 0.09mm.

That's easily in limits for a normal 0.3mm regrind, and if you do go down that route, I've got a set of 49.7mm undersize XU9 big-end shells here that are surplus to requirements

[skinner2k3 3]

Pretty egg shaped huh!

 

The bearing shells were very very worn, so didnt trust the mains too far either.

 

I have a spare engine in the garage which I am going to drop the sump off and check the shells. If the journals in that are all good I will put new bearings in and fit that.

 

Happy days

[skinner2k3 3]

Oh yeah, deffinately regrind'able (is that even a word).

 

Will see how my spare engine looks, then decide what to do.

[Team BDR 0]

The bearing shells were very very worn, so didnt trust the mains too far either.

 

Any pics for future reference?

[skinner2k3 3]

Havent taken any yet, but will do.