12 replies to this topic

[Oliverbarnes]

Hi all,

Just got my block and crank back from the machine shop and im slightly concerned about the condition of the brand new bearings i supplied them. I asked for the block to be skimmed so that a 30thou piston crown to deck clearence could be achieved, in order to do this they have obviously had to assemble the crank and rods/pistons into the block in order to measure this.

On recieveing my components back today there seems to be more wear than i would expect on the bearings i supplied? There is copper showing in places and this seems very concering since they were brand new bearings and the engine was only assembled for measuring purposes.

Whats your opinions?

[Oliverbarnes]

Picture of main bearing.

Attached Files

•  1527779988425660214016.jpg   28.02K   20 downloads

Edited by Oliverbarnes, 31 May 2018 - 03:22 PM.

[Spider]

What condition is the crank in?

 

Perhaps some more photos of all the shells and the crank may help too.

[Rorf]

They probably assembled the crank and big ends dry - those look like scratch marks, dirt etc picked up in the machine shop. 

[Thelowrider]

As said above what condition are the journals in, and also the rest of the bearings. From that one bearing It’s difficult to tell.

[Oliverbarnes]

Crank had just had a fresh 10 thou regrind and polish so is spotless, ill attach some more photos of the bearings. The third photo of the big end bearing on the back shows deep scratches which i can pick up with my nail.

[Oliverbarnes]

Crank had just had a fresh 10 thou regrind and polish so is spotless, ill attach some more photos of the bearings. The third photo of the big end bearing on the back shows deep scratches which i can pick up with my nail.

Attached Files

•  15279292282871158089666.jpg   27.17K   5 downloads
•  1527929192320333958618.jpg   71.61K   4 downloads
•  1527929116865176508324.jpg   54.91K   4 downloads

[Spider]

Whoa,,,,,

Did you have your Con Rods reconditioned too?

[Oliverbarnes]

No, conrods were untouched apart from having pistons fitted. What do you think about the condition of the bearings? Something to complain about?

[Spider]

No, conrods were untouched apart from having pistons fitted. What do you think about the condition of the bearings? Something to complain about?

 

Hard to say as many shops will only carry out work to your instructions. Some are more helpful than others in this regards and will help join the dots. Some shops don't.

 

However, in regards to your Big End Bearings, while I don't have all the pieces of the puzzle here, it does appear that you could well have a con rod alignment Big End Tunnel issue.

 

I know it doesn't help here, but as a matter of course, I always have the Con Rods reconditioned on any build. The 1275 ones nearly always lean over (I haven't pulled out a straight one yet!) , occasionally, there's a twisted one and the Big End Tunnels can get out of shape. Clearly, there was something in the tunnel that did that to the shell back.

 

Another possible cause for the Big Ends looking like that (on the slipper side) is if the bores aren't aligned to the Crankshaft Mains Tunnels. Most shops won't do this unless specifically requested. Again, I'm yet to find a factory 1275 block that is right in this regards. If you only asked for a rebore, it's likely that's all they would have done.

[Oliverbarnes]

Thanks for your help with this so far, as regards to bore miss allignment and con rod re reconditioning how critical is this and is this and is this now too late to do? I think a large amount of damage to the bearings was purely lack of cleanliness on the machine shops behalve. If more work is required to be carried out i shall have it done but being 17 on an apprentice wage and this engine is becoming very expensive haha so only trying to spend money on essentials...

[Spider]

Ah, OK - yes, it's an expensive hobby !!

 

The rods can be checked and reworked, probably without removing the pistons, just depends on what (if anything) needs to be done, but an alignment check and big end tunnel check are a must in my books. If the rod(s) have a bend in them, they should be able to straighten them without removing the pistons, however, if the tunnels need re-work, then they pistons may have to come off.

 

I don't like to get in the middle of these disputes, but yes, I do have to agree that some better care should have been taken by them. Not altogether sure it's a dirty assembly at this point, as usually any foreign matter (dirt, swarf to a point etc) will become embedded in the soft bearing material and hence why my earlier question about the crank condition as while they did look marred, they were otherwise clean.

 

All the same, if there were other issues, I think / feel the shop should have checked and contacted you prior to proceeding.

[Rorf]

That scratch on the back of the shell just proves poor shop workmanship. Do a dry build first - in other words clean everything up perfectly. Install crank with lube on the bearings, thrust bearings and see if it easily spins once torqued up. Install rods with pistons but with out rings, turning the crank after each piston installed noting if there are any tight spots. If everything turns over ok then strip everything checking each bearing for odd wear marks.

 

Also a good thing to do is to plastigage each bearing to check tolerances.