Alfa Romeo Forums banner

1 - 20 of 45 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter #1 (Edited)
Hi All,

I’m rebuilding a 75 TS engine And I’m struggling to rotate the crank with new bearings . I haven’t yet attached the connecting rods so this is the crank only. The engine hasn’t been rebuilt in the past. I ordered standard bearings for a 75 Fromm classic alfa and when assembling the crank is very difficult to turn. When removing the new bearings after hand turning with oil on the bearing surface it has left marks on the ends of each of the bearings. I subsequently have put the old bearings back in And the crank spins freely as it should I am struggling to understand why this could be the case are they usually tight from factory as this is using the standard crank without machining or grinding/polish so the standard bearings should fit fine I have attached a picture of where the bearings are marking up any ideas anyone

PS; The crank his red paint on one end I’m not sure if there is indicative of a slight Size difference?

Has anyone encountered this problem before?

Thanks Phil B0CFCF71-AF65-44BA-A6A6-FD2A2D811813.jpeg
 

·
Administrator
Joined
·
4,150 Posts
Turn the bearing shells over & have a good look at the numbers. the marks on your shells look like they are actually oversized bearings, +10 or +20

Put the shells into a conrod and do it up tight, then measure the internal size --> see if that is smaller then the crank, if so it'll never work

If you are still not sure, take the lot over to an Engineering works and let them measure it up, whatever they charge will be a fraction of the mess if you try start it like that

Aye
Greig
 

·
Registered
Joined
·
1,036 Posts
make sure bearing caps are torque correctly , i had the this problem on a 105 engine and i hadn't torqued it properly so the bearing shells weren't fully round (only happens when they are fully torqued ). also you try using some Plastiguage to check clearance.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #4
Thanks Greig, strange thing is that the Back side of the shells have STD stamped into the as does the box they came in. These are for the main bearings not the con rods though I hadn’t got to them yet. I like the idea of taking them to an engineer but it’s Easter and they are all closed.
It’s very frustrating because this was was going to be the Easter break project. 😠
 

·
Registered
Joined
·
34 Posts
Discussion Starter #5
I’ll try torquing the crank down tomorrow and checking if it changes that would be fantastic. I just want to be careful not to damage the crank surface. I’ll also try to get some plastiguage tomorrow. Do you know them minimum clearance for the TS?

thanks Phil
 

·
Registered
Joined
·
34 Posts
Discussion Starter #8
Thanks gprocket the shell thickness seemed to measure the same and the binding seemed to come from the ends of the shell as in the picture.

are these out of round until correctly torqued as italcarolz suggested?

Have you heard of the incorrect stamped shells before?
 

·
Registered
Joined
·
34 Posts
Discussion Starter #10
I checked that multiple times as I marked the caps before removal and also photo the with the marking prior to disassembly. And trust me I checked those phots and the caps many times to the point of madness hoping I might discover a mistake in assembly.
I also re assembled in exactly thesame way with the old bearings and it spun super smoothly.
The crank does have some red paint on it close the rear main is there an expectation that this could be oversize?
 

·
Registered
Joined
·
34 Posts
Discussion Starter #12
The bearings are Glyco supplied through Classic Alfa. I’ve always had great service and parts from them so it seems weird that they would be the wrongly supplied.
 

·
Premium Member
Joined
·
22,988 Posts
How was it with the old bearings? Or were you able to try it?
No it should not be difficult to turn. You can tighten down one bearing at a time to see which is causing the problem, if just one. Did the engine get really hot at some point? I wonder if the bearing saddles are out of line.
Andrew
 

·
Registered
Joined
·
34 Posts
Discussion Starter #14
Hi Andrew,
The old bearings were fine and I spins freely with them still. The new bearings are tight from the outset even when the caps aren’t installed and putting them on even one by one just makes it even tighter.
 

·
Premium Member
Joined
·
22,988 Posts
They ain't right then. Bearings are pretty cheap, send back, get a new set? I've never had a set not the right size, but it's a product, I'm sure it can happen. Bummer for you with the shipping distance, etc.
With the right size bearings, crank should drop in perfectly with bearing shells in block but no caps and spin easily, no clearance that you can feel.
Andrew
 

·
Registered
Joined
·
8,922 Posts
Perhaps you should use the old bearings. Why are you changing them?.. I've seen bearings with 250,000 miles on them with almost no wear. and the oil pressure just slightly lower. if it is low oil pressure it could be something besides your main bearing clearances..
 

·
Registered
Joined
·
4,353 Posts
It wouldn't hurt to have the rods resized.
 

·
Registered
Joined
·
4,555 Posts
Are there any chamfer issues on any of the bearing edges. Did you Mark the original bearings as to where they were located. The crank journal should have radius where it meets the counter weight. The bearing neads to have clearance for that. Compare closely your new shells with the originals. I'm going from memory but have heard of such an issue before.

Ken
 

·
Registered
Joined
·
562 Posts
Have you measured the mains on the crank? Maybe the crank is slightly oversized.

Best regards,
 

·
Registered
Joined
·
34 Posts
Discussion Starter #20
Thanks it could be over sized. I just had a look at the original shells and they have 9999 on them does that mean the are undersized?
 
1 - 20 of 45 Posts
Top