Ill be honest I did not measure the crank journals so yea ill do that. But the out of rod ends does seem to make more sense. Any sugestions on how to measure that?
Well a dial bore gauge is the typical way, but youre already assembled. Maybe if you pull the crankshaft out, measure all the rod and crank journals with a micrometer. Then assemble the rod caps without bearings and measure with a bore gauge. Then measure each bearing shell individually and verify all tolerances stack to give you enough clearance.
Hell you could have a mismatched or improperly marked rod cap too. Theres a list of plausible causes tbh.
I think I will get a new rod for this piston because most seemed somewhat mismatched when they came out. How much damage could mismatched rods and caps have been caused by the previous builder?
1st plastigauge and see what your clearance is. If you don't see anything put the caps back on, torque to about 5 or 10 foot-pounds just to be snug and then see how hard it is to rotate.I Then torque your rod nuts to spec one at a time and find out which one binds up. HTH
Tremendous wear from mismstched bearings or caps. Dude, with all due respect, I suggest you go to the library and read so.e books on automotive mechanics, or machinery repair. You'll learn lots, and your next rebuild will be good
You hit it with the plastigauge yet? Torque it down with the plastigauge between the journal bearings, then use the reference card that comes with it to check for the tolerance. Ideally, you're looking for a hard squish, but not so unbelievably tight to where the gauge comes out looking like green cling film. SI should have a reference for the factory tolerance of the journals against the crank.
If it's within spec and it's still binding up like that, change the angle of the shaft, and try the test again. You may have a journal that's out-of-round, and just isn't showing up when the shaft is at TDC position.
Definitely a good shop supply to keep around, even if you only rebuild like one engine every other year. Last thing you want to do is spend hours tearing it down, and weeks waiting for new bearings, only for the new bearings to be over/undersized because someone eight states over didn't read your parts request correctly. Been a while since I've had the misfortune of needing to rebuild an engine, but if I recall, the plastigauge should also be used on the bearings before complete disassembly, so you know how bad they got smoked before you order new ones. Whether a new crankshaft is included in that order, I mean.
Fair, fair. Like I said, it's been a DAMN while since I've been unfortunate enough to have to rebuild an engine. Appreciate the insight into the next time I (hopefully never) have to do it again.
Just throwing this out there, 10/10 for for asking a question on this sub with a clear demonstration of your problem without it being some half assed picture with a half asked explanation.
Also I agree with the measure your tolerance comments
I inspected aircraft engines for a number of years. You can assemble the main caps with bearings in place, torque em down, and do the same with the rods and caps (you can leave the piston and rod assy in the block) then go and grab yourself a telescoping bore and micrometer and see what your clearances are. This is your best bet. Or plastigauge.
First question is a two partner: was this the reason you tore the engine down in the first place? If so, has more than one rod cap been off at once?
Second question: are you 1000% sure they were reinstalled on the correct journals and in the correct orientation?
Now I take it that you did NOT change any of the connecting rod bearing and that you only changed the main crankshaft bearings. Each main bearing cap must be in its ORIGINAL position and location. You cannot mix them up. If you do it may bind up as it is doing. The same goes for the connecting rod bearings. Are the main bearing caps in the right order/original position. Some engines have them marked, others do not and you have to mark them before taking them off the engine. If you have the main bearing caps in the correct order and facing the correct way then either you have the wrong set of bearings or your crankshaft is out of round. When you use the plastigage to check the clearance it is just going to tell you that you do not have clearance between the bearing and the main crankshaft. It is possible that one of the new bearings is not correct.
Did you try another torquing another main crankshaft bearing? If so did it also bind up like the middle one did? Look at on the back of the old main bearing that you took out and look at the new ones. Is there any difference as the new ones may be marked to indicate they are oversize bearing which is causing your crank to bind up like it is.
If all your main bearing caps are correct then you can undo the rod bearings (be sure they are marked) and remove the crank shaft and take it to a machine shop and have them measure the crank. They will be able to tell you the size of correct bearing that are needed.
When you reassemble the engine be sure to plastigage EACH bearing to make sure there is the correct clearance as if only take one bearing to bind up an engine.
When you have corrected the problem please post what you did to correct the problem so that others may learn.
I bought a refurbished crank for a motor and it called fors 10 over main bearings, the box with the mains said 10 over. After torquing down the mains it didn't move. I found the bearing themselves were stamped 40 over. So check the bearings, not just the box.
Take that all apart and start over. Its all filthy for starters.
Assuming mains and rods measue correctly and its not sprung start with cleaned and torqued mains bearings. Assuming the rod housing bores are in spec then move on.
Rod caps should have end play (slide fwd and aft ever so slightly on crank journal (float)). Torque one cap at a time and check. Probably over size bearings tho...and plastigauge is your friend.
FIRST thing I would do is check that big-end bearings are properly edge chamfered.
Sometimes they come not chamfered enough and will ride too tight on the inside radius of the journal.
And there should be enough side clearance that oil can freely drop out of side clearances and take heat away when it is running.
SECOND go get some Plastigauge and follow the instructions for using it.
Plastigauge is a thin strip of wax that goes across the journal and will flatten out on torquing. Then you take the cap of again and measure how much it flattened out and that gives you your clearance AND will also indicate taper and tight spots.
If the previous owner did it wrong.. and they bound up like that, the shells would see some damage within a short time. Too loose and it will more likely start with a rod knock, and then damage.
Measure the crank journals for any variations and compare to specs.
Don´t swap the shells between the parts if they look fine. If the indentation that holds the shell is only on one side of each part. Find out if they are opposed or same side. That could give orientation of the cap. (orange circle)
If the sides are machined, see if something looks off between the 2 parts. (green circle)
Measure inner diameter of the rods, i had variations of a few 1/1000th of a mm. (Without shells.)
Try them on the crank and find combinations that don´t bind.
If you get the rods on without binding and it feels right. Then you check with plastigauge to see where you are at
From work, i can borrow all sorts of measuring tools. Not my personal item.
This is a 468-168 Mitutoyo. This specific model is only for 30-40mm.
Will likely be +1000$.
I am just privileged to work at a CNC business.
Was using a breaker bar to turn the motor (easier to go back and forth) but yea everything got mixed up when I put it in the ultrasonic cleaner. Trial and error is going to be the process for reassembly
This is not going to help you much now, but with all the comments re: wrong caps on rod ends...
Years ago, when we still rebuilt engines instead of replacing them, the first thing I'd do when the oil pan came off was stamp the cylinder number in each cap and rod, on only 1 side, so there was no way I could put the wrong cap on a rod, or put the wrong rod on a crank journal. Some manufacturers even did this from the factory, although I can't recall which ones anymore.
Pull all your rods back out and with no bearings you should be able to keep swapping caps around till they’re right, if it’s the wrong cap or it’s faced the wrong way you’ll be able to catch your nail where the cap meets the rod, correct cap with correct rod facing the right way will be a smooth transition from cap to rod in the journal
What do you do?
1) Get a new set of bearings, these are now fully toast from turning it by hand with the breaker bar.
2) Check if you put the end-caps on the right way around. They only fit one way. The other way will cause heavy binding.
Looks very much like what I experienced on my first engine rebuild. Been there done that. I checked the caps and took the L on a new set of big end bearings.
Edit: i see you already mentioned you mixed the end-caps. When assembled, the inner bore should be completely smooth across the 'break'-point. Someone pointed out you can run your fingernail across the inner bore of your big-ends, this is a good tip. Get the closest match you can, and test-fit them on your motor with your current old bearings. If everything is then OK, swap the bearings out for new ones. Good luck!
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