Alfa Romeo Forums banner

21 - 28 of 28 Posts

·
Registered
Joined
·
336 Posts
Plastigauge doesn't check any of those items I listed. It's quite possible you're confused and have your terminology mixed up. You started by asking about the bore for the main bearings.
You should get and read a manual on basic engine rebuilding.
 

·
Premium Member
Joined
·
15,415 Posts
If these were nitrided, I wouldn't worry too much about throws being out of round, etc. Do not overthink this. The cranks themselves are/were very stout compared to many cars.

If it is nitrided, do not let anyone grind it.
 

·
Registered
Joined
·
336 Posts
If these were nitrided, I wouldn't worry too much about throws being out of round, etc. Do not overthink this. The cranks themselves are/were very stout compared to many cars.

If it is nitrided, do not let anyone grind it.
I would tend to agree. However, these are older engines, and many, if not most, have been opened by others in the past. It's something I just do in a complete rebuild.
I'm unsure how far the nitride hardness extends. On RR crankshafts a 0.010" regrind could done without the need to reharden the crank.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #24
Plastigauge doesn't check any of those items I listed. It's quite possible you're confused and have your terminology mixed up. You started by asking about the bore for the main bearings.
You should get and read a manual on basic engine rebuilding.
I have several engine rebuild books and im sure i read them many years ago, have built a few engines im no expert but i know what im doing at this level, i just need information on whats allowable on the Nord as the measurements are not to standard and im asking the kind people on here for their knowledge before i spend my hard earned cash on the shiny bits
crank journals are good they are round and in spec, i dont have the equipment to test for warped crank but assume if clearances are good and it rotates freely without changing resistance all is good, if you have a diy way to test the crank im all ears
 

·
Registered
Joined
·
336 Posts
You seem to have access to some expensive measuring tools. All you need to check the crank for straightness is a dial indicator. Place main bearing #1 and #5 in the block, lay the crank on top and measure run out at the center main journal with a dial indicator as the crank is rotated. Checking the journals for roundness simply entails measuring the journal diameter at 2 places and comparing the measurements. This should all be laid out in the books you have.
 

·
Premium Member
Joined
·
670 Posts
Chas, I am not an engine builder, but have built more than a few. If the plastigage method checks out and the crank spins with bearings/oil and the caps torqued, all is good.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #27
You seem to have access to some expensive measuring tools. All you need to check the crank for straightness is a dial indicator. Place main bearing #1 and #5 in the block, lay the crank on top and measure run out at the center main journal with a dial indicator as the crank is rotated. Checking the journals for roundness simply entails measuring the journal diameter at 2 places and comparing the measurements. This should all be laid out in the books you have.
Never thought of that, I can definitely do that, I have checked journals on crank and they are good, thanks for the tip
 

·
Registered
Joined
·
336 Posts
Chas, I am not an engine builder, but have built more than a few. If the plastigage method checks out and the crank spins with bearings/oil and the caps torqued, all is good.
You do your engines your way, I'll do them my way. I don't buy bearings until I'm sure of what size I need. Plastigage does not indicate roundness or straightness well and I rarely use it. I do check how easily the crankshaft turns when all is tightened down using a very thin oil.
 
21 - 28 of 28 Posts
Top