Conrod bearings - mis-stamped

James Gelido

James Gelido

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Hey Guys!




Bad news  Had the crank shaft freshly ground for the Conrod bearings we had been sent. Unfortunately, although the Conrod Bearings were stamped with measurement, when we went to fit, was wrong. We must have misunderstood the marking of .3 (as shown on bearing) to be 0.30ths rather than 0.3mm.

We were so close yet so far, almost was in tears after waiting 1.5 years for this engine. Now need to source correct bearings of 0.0030THS (0.0762MM). Could anybody help or know where I can source within Australia? Really don't want to source parts from France. Otherwise will grind crank big ends down to .8 (as I found we do have .8 bearings).

A sad day,




Thanks in advance guys,




James
 
Last edited:
What engine? I doubt you’ll find a 0.003” undersize bearing for anything. At least you can grind the crank down further. The correct method is to fit the bearings (no crank), measure the hole, add the clearance, then get the crank ground to match.
 
James Gelido said:
Hey Guys!




Bad news  Had the crank shaft freshly ground for the Conrod bearings we had been sent. Unfortunately, although the Conrod Bearings were stamped with measurement, when we went to fit, was wrong. We must have misunderstood the marking of .3 (as shown on bearing) to be 0.30ths rather than 0.3mm.

We were so close yet so far, almost was in tears after waiting 1.5 years for this engine. Now need to source correct bearings of 0.0030THS (0.0762MM). Could anybody help or know where I can source within Australia? Really don't want to source parts from France. Otherwise will grind crank big ends down to .8 (as I found we do have .8 bearings).

A sad day,




Thanks in advance guys,




James
Click to expand...

Good machine shops ask you to give them the block, bearings and rods with bearings before they embark on grinding your crank because they do as Peter says. They measure stuff and then grind to fit. I suggest you take all that with you to the shop next time even if they didn't ask for it. Or change shops to one where they ask for it without you prompting them.

One shop where I had some work done discovered there was a slight misalignment in the main bearings' tunnel in the block so they recommended a line bore as well. And no, they didn't upsell me. I checked the tunnel before approving the work and they were right.

Not all shops are equal.
 
PeterT said:
What engine? I doubt you’ll find a 0.003” undersize bearing for anything. At least you can grind the crank down further. The correct method is to fit the bearings (no crank), measure the hole, add the clearance, then get the crank ground to match.
Click to expand...

403 engine. Thats what I thought, not likely. I will have to bite the bullet and grind the crank once again. Won't take much.
 
PeterT said:
What engine? I doubt you’ll find a 0.003” undersize bearing for anything. At least you can grind the crank down further. The correct method is to fit the bearings (no crank), measure the hole, add the clearance, then get the crank ground to match.
Click to expand...

403 engine. Thats what I thought, not likely. I will have to bite the bullet and grind the crank once again. Won't take much.
 
schlitzaugen said:
Good machine shops ask you to give them the block, bearings and rods with bearings before they embark on grinding your crank because they do as Peter says. They measure stuff and then grind to fit. I suggest you take all that with you to the shop next time even if they didn't ask for it. Or change shops to one where they ask for it without you prompting them.

One shop where I had some work done discovered there was a slight misalignment in the main bearings' tunnel in the block so they recommended a line bore as well. And no, they didn't upsell me. I checked the tunnel before approving the work and they were right.

Not all shops are equal.
Click to expand...

Thanks for that. I did give them everything; block, conrod bearings, mains, and rod. Practically whole bottom end. Funny enough, the guy said 'don't assume anything' before grinding but still managed to assume that.3 stamp meant .30ths not .3mm. To their defense, they did an excellent job on the head! The issue can be rectified, just frustrating. One small/BIG mistake.
 
It's marked in either inches or millimetres, and if it was assumed to be inches, .3 is close to 1/3", which is clearly not going to be right.
 
Something like this happened to me in 1987 with a 404 KF2 engine. The machine shop said it had been ground to 0.3 mm but I didn't check with Plastigage during assembly. Started her up - good at first then oil light started to flicker....and after 5 minutes it shredded the bearings and the crank was destroyed. Guy had probably done 1 mm or something crazy. It was BAD!

I had a second crank and that one was done properly and the Plastigage verified it was good and it went well. Still have that crank as a spare. It was from a ZF car so I had to get the pilot shaft bearing pressed into the end first.
 
James Gelido said:
Thanks for that. I did give them everything; block, conrod bearings, mains, and rod. Practically whole bottom end. Funny enough, the guy said 'don't assume anything' before grinding but still managed to assume that.3 stamp meant .30ths not .3mm. To their defense, they did an excellent job on the head! The issue can be rectified, just frustrating. One small/BIG mistake.
Click to expand...

Clearly their fault then. They should be happy to have the opportunity to correct their mistake.
 
Mike Tippett said:
Something like this happened to me in 1987 with a 404 KF2 engine. The machine shop said it had been ground to 0.3 mm but I didn't check with Plastigage during assembly. Started her up - good at first then oil light started to flicker....and after 5 minutes it shredded the bearings and the crank was destroyed. Guy had probably done 1 mm or something crazy. It was BAD!

I had a second crank and that one was done properly and the Plastigage verified it was good and it went well. Still have that crank as a spare. It was from a ZF car so I had to get the pilot shaft bearing pressed into the end first.
Click to expand...


Unbelievable! What a pain. 1 step forwards, 2 steps backwards. Did the guy resolve the issue or provide any compensation? Thankfully the engineer did a trial fit for ours and saw the movement and notified me. It can be such a morale destroyer.

Have to keep pressing forwards though!
 
The second crank was reground for "free" but I got no compensation for the ruined crank. But the fault was partly mine for not plastigaging it.
 
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