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Spun a big end shell!!


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If its what I think it is, then yeah its my fault this has happened, but live and learn. Notched my block out for my scat rods, they all looked like they had sufficient clearance from the rod to the bore, or so I thought..... if the rod was skimming a bore, would that be enough to spin a shell? all the rod bolts were tightened to correct torque, engine was cleaned out after notching etc etc



what are your suggestions?


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Id say more oil related than the rod hitting the block.

Agree with this, I take it you've done a visual inspection of the rod to check that there actually was clearance issues between the rod and the cylinder by witness marks?

What were your oil clearances and what oil were you using?

Edited by AdamB
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Havent yet got the rod out, surely if there was an oil problem the rod would be discoloured from heat? the only thing I had to run in was the bores and piston rings, was using mineral oil for the first 100 miles then put 10/40 semi synth in.



how would you even check the oil clearances? if it helps the crank journals are std size using new acl std size shells.



gunna get the engine out and strip to see the clearances of the rod to the bore, how much shit from the shell do you think is around my engine now?


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Not necessarily, as it depends when it occurred, if it was at full throttle under heavy load when the engine is under its most stress chances are the rod will have blued. During light cruising or idle it would have very little effect on the rod itself, and you will no doubt find the big end journal is still perfectly within its circularity tolerance, remember its cheaper and easier to replace bearings than a rod.



Why did you swap over oils so soon? Mineral oil should be used up until 1200-1500 miles before swapping.



Did you build an engine without even checking the oil clearances?


There's two ways of checking oil clearances, either using plastigauge or measuring the internal diameters of the journal and deducting it from the crank journal diameter.

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but if thats the case regarding the oil clearances, how comes the other 3 are okay? this one scored the crank journal so gotta be changed, im considering selling the pistons and rods if theyre in good condition then just buying a forged engine from someone on here thats already run in and running smooth


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update:


ripped the engine apart, rods and pistons out, everything unplugged ready to drop the block out. Rod no.1 is going in the bin, the big end of the rod is torn up, one side of the rod is discoloured from heat.



Think maybe an oil pressure problem? oil pump? clogged crank journal holes? found 2 more big end shells on their way out, one of them was tapering quite badly :(



need help people please


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Im thinking either oil pump or crank journey holes clogged up, the oil pump hasnt ever been changed and the engines covered 105k.



something to consider, the block never left the car in the first place, had the bores honed to correct clearances, all the bores were measured properly for ovality and they were fine, i notched the block while the crank was still in the car but did my best to cover the crank so all the crap didnt get on the crank, but whats your opinions? besides me being retarded haha


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yeah made sure all rods were with the correct caps and that the rods were facing the right direction as apparently they have a direction because of the little notches in the big end where the shells sit you know? all the rods were at the right torque setting, even when taking the rods off they were still at the right torque.



and crank what by hand sorry?


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They have certain positions one con rod has one position on the crank they aren't interchangeable, and they do have a direction to face etc yeah.

Once the engine was built did you turn the engine over by hand from the bottom pulley to check the feeling of the engine?

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yeah I did, it turned over fine? before i bolted the rods up I put each rod individually on each journal upside down with the shell on and assembly paste to check if the rod turned freely on the crank, they were all fine


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Im thinking either oil pump or crank journey holes clogged up, the oil pump hasnt ever been changed and the engines covered 105k.

Theres your problem then. I don't understand for the sake of £100 why people don't change the oil pump. Was it actually ever removed from the block?

For a small amount you've made a costly mistake. Sorry to put it bluntly.

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only reason i didnt change it was cause it was fine before the rebuild and I didnt take the block out so I didnt bother changing it, I know I deserve to be laughed at for this, my mistake but live and learn aye, live and learn with a £1000 down the drain lol


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I didnt want to go through the hassle of taking the crank out, plus getting the gear box out too I wasnt too clued up on how to do it despite reading through a lot of threads, I was on a bit of a budget too, but now im aware that you cant spare any expense.



how comes it wouldnt have lasted?


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Fair enough for having a go like, but as you found out to your cost, it needs to be done properly.

I don't think it would have lasted because the block wasn't chemically cleaned and oil galleries cleared out, years worth of carbon build up and debris would have soon found its way circulating your fresh engine and would have destroyed the bearings, bores etc.

It may well be even because of this that the bearing has spun because oil pressure would be low due to sludge build up blocking oilways, however thats me speculating.

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but like i said before it was fine, even the big end shells from the old rods were good enough to use again (i didnt obviously but yeah) if it was blocking oilways then how comes it didnt screw my engine before? youre right in what you are saying but in this situation Im not sure this is what's happened


Edited by EPnick22
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Whether they are standard size shells or not, you can't just drop new ones in there without checking the clearances IMO. I'd put that on being the problem. The other ones that haven't done it.. You've either got lucky or it would be a ticking time bomb

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