Number on crankshaft big end caps

[Rupunzell]

On piston ring gaps, better to be slightly larger than smaller. The number ONE cause of piston ring failure is too small of an end gap. The rings and piston expand heated up. If the piston ring ends come in contact with each other, the resulting force can easily shatter the piston ring causing near instant piston failure and piston binding to the cylinder. The common rule of thumb is no less than 0.004" per inch of cylinder diameter.. And, orient the piston rings properly.

Bernice

 

[fiatfactory]

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.

easy to tell. as the block is also stamped with the same 4 digit number to identify it and the caps as a "matched set" so all you need to do is confirm you have the same number all over... if you dont and cant find the full set, then the block is kinda useless until you have it align bored in the bearing tunnel.

if you "swapped blocks" did you swap pistons into a different block as well?

Standard bores are class sized, and the bore is matched to a piston of the same class.... you might have too tight piston to bore clearances if you've fiited a D class piston into an A class bore...


SteveC

 

[Mxgrds]

The engine has always kept running. It didn’t seized completely. The problem was it binded to much for the starter motor to get it round. If it were a piston problem I imagine It should not be possible to turn it by hand, heavy resistance though. So binding of the main caps seems to be the most likely candidate. Luckely I have all parts complete of the two blocks. Next is to sort out what is on which block. Repair can be done while engine in. Not ideal but doable.

 

[fiatfactory]

The engine has always kept running. It didn’t seized completely. The problem was it binded to much for the starter motor to get it round. If it were a piston problem I imagine It should not be possible to turn it by hand, heavy resistance though. So binding of the main caps seems to be the most likely candidate. Luckely I have all parts complete of the two blocks. Next is to sort out what is on which block. Repair can be done while engine in. Not ideal but doable.

Actually I think it would more likely be the other way around.. a mismatch of main caps would almost certainly lock the engine solid when cold while it was still on the engine stand, if it didn't I would be very surprised.

A mismatch of piston classes, well your talking differences to the second decimal place so it would be tight, but not necessarily lock up...as it got hotter the piston to bore would definitely close up/get tighter

You did say it didn't "seize completely" .... does this mean it stopped while running? and then was unable to start / turn over due to being tight?

If you have all the other parts, then easy to tell if you've mixed things up... the second block will also have a four digit number stamped on the block and on all five main caps, if you have any numbers that mismatch then you have your problem... but if the spare block has all mactching numbers then it will sort of confirm the piston to bore or piston ring clearance issue

SteveC

 

[Mxgrds]

If the engine runs it keeps on running, also at low rpm. But once I shut it off it won’t turn anymore by the starter motor.

 

[fiatfactory]

are you sure your starter motor is good? things being hot also increases electrical resistance... it could be brushes and bushes... if all you get is "click - click" then maybe the solenoid is shagged

SteveC

 

[Mxgrds]

are you sure your starter motor is good? things being hot also increases electrical resistance... it could be brushes and bushes... if all you get is "click - click" then maybe the solenoid is shagged

SteveC

It does say click, but it also turns the engine a bit. If it was the starter motor it would not explain the heavy turning by hand when warm.

 

[Mxgrds]

Matching numbers on the spare block. Therefor also in the block in the car.

 

[Mxgrds]

I did some honing myself with a cheap tool. It looked ok to my (amature) opinion. COuld it be that I have not enough lubrication on the cylinder walls?

 

[carl]

I doubt it. I have done lots of Fiat cylinder honing with cheap tools and never had the issue you have.

 

[Dr.Jeff]

COuld it be that I have not enough lubrication on the cylinder walls?

I also doubt it.
I've known lots of people (including "professional" shops) that didn't even bother to hone the cylinders and it worked. But I'm certainly not saying it's best practice not to hone. Just that your issue isn't likely that you did it yourself.

 

[Mxgrds]

How to check the piston play? If I switched pistons between the blocks, the pistons in the spare block must have more play than standard. How much play should there be?

 

[speedy fiat]

Have the caps been put on in the wrong order i.e. number one where number five should be and visa versa. Are the caps facing the right way? (I've done both) Loosen the caps off one by one and try to rotate the engine by hand to see when the problem goes away. You can then move onto the big end caps to test them. Then remove the big end caps and knock the pistons up the bores to test the pistons. I appreciate that isn't the easiest solution with the engine in the car, but given that the engine is becoming so tight it would suggest an engine out job to investigate bearing and/or other damage

 

[Dr.Jeff]

At this point it would be easier to drop the engine and tear it back down. You will likely have to anyway to remedy the situation. They come out easily and working on them is SOOO much easier on a stand.

 

[carl]

The shop manual indicates how to check piston clearance with feeler gauges. If you mixed and matched pistons from two different motors I can see a possible problem. As noted by the doctor, it's probably time to pull the motor.

 

[Mxgrds]

Have the caps been put on in the wrong order i.e. number one where number five should be and visa versa. Are the caps facing the right way? (I've done both) Loosen the caps off one by one and try to rotate the engine by hand to see when the problem goes away. You can then move onto the big end caps to test them. Then remove the big end caps and knock the pistons up the bores to test the pistons. I appreciate that isn't the easiest solution with the engine in the car, but given that the engine is becoming so tight it would suggest an engine out job to investigate bearing and/or other damage

Another thing to check. Are they in the right order? And the crankshaft, is that numbered? Shouldn’t that fit with the end caps?

 

[fiatfactory]

How to check the piston play? If I switched pistons between the blocks, the pistons in the spare block must have more play than standard. How much play should there be?

both blocks not only have identifying numbers for the main caps, they also have identifying LETTERS stamped onto the sump flange to identify the bore class. Alongside each bore will be a letter, A is smallest ranging up to E which is largest.

to confrm my suspicion, you will need both sumps off.

If you've swapped pistons, I'm kind of guessing that you would take the easy route and swap the piston and conrod, and I'm assuming the rods and pistons stayed together and you didn't remove and refit the gudgeon pin clips, and like most people would have installed the piston attached to conrod numbered 1 into bore number 1.

So what you need to do is compare the letters stamped alongside each bore.

if the block in the car now is (for example) marked from 1 to 4 as A / B / B / A and your spare is marked perhaps A / B / C / D ... an you've used the pistons from the spare, then number 3 will be a little tight, and number 4 will be quiite tight piston to bore... you are needing to measure to the second decimal place, a feeler guage just won't cut it.

SteveC

 

[Dr.Jeff]

I'd have to go back and re-read, but I thought he said he installed new pistons?

 

[Mxgrds]

No new pistons and thanks for this amazing help.

 

[Mxgrds]

These letters? CCBB. I am sure I installed them in the same order as they came out, but not if from the same block. As explained earlier I switched blocks halfway and might have just switched installed pistons to the other block. If the pistons in the spare block don’t match the block then I have a problem and a possible solution.