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

[kbmb02]

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

 

 

 

 

[TobyB]

Did the other half of the shell have any oil holes in it?

 

t

[kbmb02]

T is in the game. (I haven't pulled the crankshaft yet ... don't believe it's necessary to spot the oddity). -KB

[roadhog0]

Some rod got starved of oil. Only one main, dont know which one... But one main is suppose to have 4 holes, the rest have 2. (Not counting the large main)

 

Picture From IE's website

[ndog]

^x2 wrong bearing (big end bearing) in/on wrong piston 

. complete guess

[kbmb02]

Think about the function of the additional oil holes in the bearings ... then look at the photo again.

   (Sorry, this may be goofy - but it is worthy of a discussion). -KB

[roadhog0]

Hmmm, There's no oil gally in that main bearing cap!

[kbmb02]

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

[ndog]

ken this may sound dumb but is that a bearing in the cap

(both bearings)are in the photo?

Edited October 13, 2013 by ndog

[kbmb02]

ken this may sound dumb but is that a bearing in the cap

(both bearings)are in the photo?

 

No - the cap is bare (that's the bearing from it).

[FB73tii]

+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

[ndog]

thanks fred,   u said that better

[kbmb02]

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

[ndog]

how do the bearings cool or lubricate w/o galley?  The engine never had oil nozzels to spray the piston skirts not that that would/could help the lower end?????

nasty photo btw

Edited October 13, 2013 by ndog

[Tommy]

...

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