Number on crankshaft big end caps

Mxgrds

Mxgrds

True Classic
Does anybody know what the number on the big end caps, that hold the crankshaft, means?
I did a revision on a uno 1.3 turbo block and might have switched some parts with a spare block. Now the engine has lots of friction when it gets warm. So much friction that the startermotor won’t get it around anymore. Maybe I switched the end caps by mistake.
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I always considered that the serial number of the engine. Or maybe it's a sequence number or something like that. They will all match. I like to stamp that number on the block, just above the part number, to ID that engine when everything is buttoned up. I use it for the engine ID.
And yes, if you put the wrong caps on the wrong block you may have to line bore the block.
If that's your problem you should see some weird looking wear on the main bearings.
 
Main journals and rod journals just don't expand enough going from cold to hot to create much of a difference in oil clearance. So if your oil clearance is in spec when cold, it will be in spec when hot. So for a home mechanic freshening up an engine, that means that when all caps are torqued to spec, if the crank spins with the proper resistance when cold, it will still do so when hot.

Much more likely to be influenced by hot or cold is piston bore clearance. Pistons and to a lesser extent bores do indeed expand enough between cold and hot to create a high friction situation. At my buddy's machine shop, in the winter time when shop temperatures are lower and he is doing the final power hone on an engine block's cylinders, he will soak pistons in warm water before he measures them for their individual bores, thereby accounting for expansion and contraction.

Mike is of course correct when he states that if main caps are mixed up between two blocks, the solution (other than to "un-mix-up" them) is a trip to the machine shop for a line hone or line bore.

What other diagnosis have you done on this condition?

If the symptom is hard hot starting based on the starter motor having trouble turning over the engine when hot, well that could be a bad starter motor or bad wiring. What have you done to eliminate that possibility?

Have you taken any steps to measure the torque needed to spin the crank when cold vs how much is needed when hot? I would think that a torque wrench or spring scale applied to the crank pulley nut when cold vs when hot could help answer that question. You would take the plugs out to eliminate any compression-related variances, then start from a constant rotational position, say BDC, then pull the wrench and observe the dial or pointer or scale to measure, then repeat the process when hot. Of course this does not isolate the mains or rods as the pistons are still connected, but it would provide data that would absolve or condemn the starter.

It would be useful to use and endoscope or borescope to look thru the spark plug holes and at the bores for scuffing, which should be evident if the pistons have been fitted too tightly and are expanding when hot to the point where they are past the tight end of their fitment.
 
Dan raises a good point, more probably the starter. I too would test how easy to rotate motor by hand in hot and cold environment. Also, not that hard to drop the oil pan and access these caps with the motor in the car. You have to support the trans and then remove the cross member. Then you have full access to the oil pan.
 
Dan Sarandrea (Phila) said:
Main journals and rod journals just don't expand enough going from cold to hot to create much of a difference in oil clearance. So if your oil clearance is in spec when cold, it will be in spec when hot. So for a home mechanic freshening up an engine, that means that when all caps are torqued to spec, if the crank spins with the proper resistance when cold, it will still do so when hot.

Much more likely to be influenced by hot or cold is piston bore clearance. Pistons and to a lesser extent bores do indeed expand enough between cold and hot to create a high friction situation. At my buddy's machine shop, in the winter time when shop temperatures are lower and he is doing the final power hone on an engine block's cylinders, he will soak pistons in warm water before he measures them for their individual bores, thereby accounting for expansion and contraction.

Mike is of course correct when he states that if main caps are mixed up between two blocks, the solution (other than to "un-mix-up" them) is a trip to the machine shop for a line hone or line bore.

What other diagnosis have you done on this condition?

If the symptom is hard hot starting based on the starter motor having trouble turning over the engine when hot, well that could be a bad starter motor or bad wiring. What have you done to eliminate that possibility?

Have you taken any steps to measure the torque needed to spin the crank when cold vs how much is needed when hot? I would think that a torque wrench or spring scale applied to the crank pulley nut when cold vs when hot could help answer that question. You would take the plugs out to eliminate any compression-related variances, then start from a constant rotational position, say BDC, then pull the wrench and observe the dial or pointer or scale to measure, then repeat the process when hot. Of course this does not isolate the mains or rods as the pistons are still connected, but it would provide data that would absolve or condemn the starter.

It would be useful to use and endoscope or borescope to look thru the spark plug holes and at the bores for scuffing, which should be evident if the pistons have been fitted too tightly and are expanding when hot to the point where they are past the tight end of their fitment.
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All this crossed my mind too. So I checked turning the crankshaft with a wrench when cold. Engine turns over smoothly as You would expect. When warm however, it is very difficult an goes not smooth but with little shocks. Typically a friction. The feeling it gives, it had to be the pistons or piston ring cap. That means the engine has to come out again.
 
carl said:
Dan raises a good point, more probably the starter. I too would test how easy to rotate motor by hand in hot and cold environment. Also, not that hard to drop the oil pan and access these caps with the motor in the car. You have to support the trans and then remove the cross member. Then you have full access to the oil pan.
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I did that already. I also noticed I made an error putting things back. One of the end caps had a different number. And I used a wrong bearing shell on one. Amature!
 
Mxgrds said:
I also noticed I made an error putting things back. One of the end caps had a different number. And I used a wrong bearing shell on one.....
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These should be corrected of course. After correction it would be useful to note whether or not spinning the crank takes less force. I would be very surprised if this is the root of the problem, given that you stated it spins freely when cold but not hot.

Can you be more specific about what was done to each component of the short block?
A. Crank main journals polished but not ground?
B. Crank main journals ground to an undersize?
C. Main bearings replaced with standard or oversized?
D. Crank rod journals polished but not ground?
E. Crank rod journals ground to an undersize?
F. Rod big end bearings replaced with standard but rods not reconditioned?
G. Rod big end bearings replaced with oversized bearings?
H. Cylinder walls (a) cleaned only; (b) honed but not bored (and if so by home mechanic or at machine shop?); bored and honed to next oversize?
I. Pistons and rings (a) re-used; (b) replaced with new standard size; (c) replaced with new oversize?
J. If pistons replaced with new oversize, was the block professionally bored and honed with each piston fitted to a particular bore?
 
A. Crank main journals polished but not ground? -> no
B. Crank main journals ground to an undersize? -> no
C. Main bearings replaced with standard or oversized? -> standard
D. Crank rod journals polished but not ground? -> no
E. Crank rod journals ground to an undersize? -> no
F. Rod big end bearings replaced with standard but rods not reconditioned? -> standard
G. Rod big end bearings replaced with oversized bearings? -> no
H. Cylinder walls (a) cleaned only; (b) honed but not bored (and if so by home mechanic or at machine shop?); bored and honed to next oversize? Honed by home mechanic (me)
I. Pistons and rings (a) re-used; (b) replaced with new standard size; (c) replaced with new oversize? -> new standard size
J. If pistons replaced with new oversize, was the block professionally bored and honed with each piston fitted to a particular bore? -> no, no standard pistons
 
Mxgrds said:
I did that already. I also noticed I made an error putting things back. One of the end caps had a different number. And I used a wrong bearing shell on one. Amature!
Click to expand...

THIS is most likely the issue. Replace the main bearings with new & replace the mis-matched end cap with the correct original (numbers-matching) cap.

All stamped numbers on the end caps should match each other, & these should also match the number stamped on the oil pan mounting face of the engine block (usually around the oil pump mounting area, or sometimes on the opposite side).
 
Agree with Stich. Also could it have spun a bearing, giving that sort of feel when turning the crank? However that typically also makes a lot of noise when it runs.

As for the list of things changed/work performed. Over the years I've done pretty much every combination; either due to not knowing better, not having the budget, or not caring. Oddly there hasn't been any real relationship between what I've done and how well it turned out. But for the most part my approach with a good running engine that's just tired and in need of a refresh is to clean and measure everything. Assuming things are still within tolerance and no damage, then I reuse the same pistons, rods, and crank, and replace the rings, bearings, and seals/gaskets. However I do hone the cylinders, polish all crank journals, and clean up all deck surfaces (I have the equipment for those tasks in my shop but I'm certainly no pro at it). Seems to work out quite well. But I also agree the "best" approach would be to buy everything new and have everything machined to perfect tolerances.
 
The normal items all look correct. The notches on the end caps relate to which end cap bearing they are, and you are in order from 1 to 5, right to left in the pic. The number stamped on all of them lets you know which end cap goes with which block. If you mix them up, they will not fit. It looks like they are all the same number, but hard to see the two on the left. Are we sure these end caps came from this block? The end caps and block are center lined honed from the factory, so if you mix them up it would have issues.

However, I think the bearing is probably wrong. Even though the engine is in the car, you will probably need to pull it out and fix it. You can drop the pan, pull the bearings and take a look before the whole engine comes out. By what you are saying, if it is bearings, one should show damage.
 
Given the symptoms you describe (turns hard and with little jerks when warm) and the possibility that you used a main end cap from a different block.... if it were my motor I’d be pulling it out and opening it up again. See if you can identify the mismatching cap and get the right one in there instead. Be prepared to replace one or more bearing shells, and plastigage all the journals before you put it back together.
 
Did you check and adjust the gap on the new piston rings? If they are too small, as the rings heat up, they will bind (or break).
 
PaulD said:
Did you check and adjust the gap on the new piston rings? If they are too small, as the rings heat up, they will bind (or break).
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I think Paul is on the right track, even dirt and carbon build up in the ring groove that hasn't been properly cleaned away will cause the ring to become tighter when hot...

But an incorrect cap and a misplaced bearing certainly won't help, but shouldn't get tighter when hot, well not unless the bearing is breaking down with heat. (usually) ... if there was sufficient misalignment the cank would lock up / be hard to turn when cold as well when the caps were torqued up (usually)

If you'e made fundamental assembly errors, make sure you have a workshop manual handy when you go for try number two, and make sure you have the thrust washers in the right way. (something often done wrong)

SteveC
 
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I had an X motor with a very noticeable bearing knock. Turned out one crank bearing cap was not from that motor and I didn't have the correct one. I had to throw the block away.
 
I might have well switched all caps between the two blocks. I did not know these were belonging to a particular block. The plan was to use my first block but I already cleaned a block I bought. So halfway I switched blocks and might have taken the caps from one to another. Can’t remember.
 
The main caps are ~line bored~ after they are torqued to spec during Fiat production of these engine blocks. They are NOT interchangeable between engine blocks. If they are mixed up, there will be binding of the crank due to main bearing out of proper alignment... which can cause an engine failure.

There is a LOT of casing technology in these Lampredi designed engines that makes them excellent in many ways. Thin wall cast iron which is not so easy to do, the cylinders are siamese with a closed top deck to make the cylinders strong and very rigid. The bore size of 86mm is no mistake as this is near the ideal flame prorogation diameter. This plus short stroke and a number of other race engine design parameters makes this Lampredi more of a race motor than a production motor.. or why a stock Lampredi SOHC engine can easily spin to past 8,000 rpm with little problem or being over stressed.

Knowing this, treat this engine like any other high precision device knowing all it's parts are high precision and not "slapped together"..

The other potential source of extreme grief, auxiliary shaft bearings.. Leave these ALONE...

Bernice
 
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