Jump to content

Sunday Game: Main Bearing, Guess What's Wrong.


kbmb02

Recommended Posts

I've just taken over the care-taking of a race car which hasn't exactly been reliable ... including a recently seized engine.

 

Photo shows an M10 main cap and bearing and an 'interesting' issue (this was amongst several "What were they thinking?" observations discovered during tear-down and forensics. A correct guess will be rewarded with a  photo of what occurred to the #3 connecting rod (both bolts were used to affix the cap, btw)... -KB

 

 

 

 

post-35761-0-76812600-1381680806_thumb.j

Link to comment
Share on other sites

Ding ding ding .. yep, that's it. All the early* M10 blocks I've seen do not have an oil galley (or back-groove) in the main bearing saddles and caps. Hence, the oil holes - and extra oil holes - serve no function. The previous engine builder missed this, apparently.

 

*Early blocks - to the best I've been able to ascertain - are those where the oil dipstick is part of bolt-on housing. I've got a buddy who often mentions that while engines without the back-groove / oil galley are sufficient for street cars, using the early blocks for high-stress race engine is risky.

 

Those with supporting or contradictory information can post here... -KB

Link to comment
Share on other sites

+1^^ Based on the photo I was going to say they used a rod bearing for the main bearing--that really wouldn't work! Noticed the lack of the oil galley back-cut, but even though the holes not needed on that side, they wouldn't cause a problem, would they? Not sure if you can get bearings without holes, other than by special order.

 

--Fred

Link to comment
Share on other sites

It's not the (extra) holes, themselves, which are the problem - the holes are simply pointless without the back groove / oil galley.

 

What I'm suggesting is the absence of the oil galley (in the early blocks) is an issue to be aware of. The reason for adding extra holes is to redistribute oil to where it's needed in racing applications (where failure was found, back in the day) - such as #3 connecting rod journal.

 

Speaking of which, here's that toasty connecting rod...    -KB

post-35761-0-39372000-1381698377_thumb.j

Link to comment
Share on other sites

...

What I'm suggesting is the absence of the oil galley (in the early blocks) is an issue to be aware of. The reason for adding extra holes is to redistribute oil to where it's needed in racing applications (where failure was found, back in the day) - such as #3 connecting rod journal.

...

 

I have seen those race prepped bearings for sale but never really knew what was done. Could you explain where exactly the extra holes should be? Do they only work with later blocks with the groove?

 

Also the weakness of early blocks was new for me. Still learning...

 

   -Tommy

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Upcoming Events

×
×
  • Create New...