migti 0 Posted February 5, 2006 hi all i have just bought an alloy mi engine in bits the big end bearing caps have not been marked on removal and i was informed the need to be fitted back to correct rod ect somthing to do with machining anyone any ideas??? Cheers Share this post Link to post Share on other sites
M3Evo 0 Posted February 5, 2006 (edited) Oh dear, yeah they need to be assembled with the rod they came from as they're machined as an assembly so likely as not, no two caps will be exactly alike No ideas about finding out which came from where though. Aren't any distinctive marks in the grime on them that might match up or something are there? Edited February 5, 2006 by M3Evo Share this post Link to post Share on other sites
Ryan 99 Posted February 5, 2006 When bolted together the sides of the rod+cap should be smooth as they are machined together in the factory. Trial fit each cap to a rod and see if you can feel an obvious lip where the 2 parts meet. Also the small cut-outs that hold the bearings in place should both be at the same end, so that cuts down the number combinations you'll need to try. Share this post Link to post Share on other sites
PumaRacing 2 Posted February 5, 2006 hi all i have just bought an alloy mi engine in bits the big end bearing caps have not been marked on removal and i was informed the need to be fitted back to correct rod ect somthing to do with machining anyone any ideas??? Cheers This should be a straightforward matter of "audit trail analysis" of a damaged or already dismantled engine. If you fit each cap in turn to a rod and examine it under a good light you'll see distinctive machining marks in both halves from the original factory honing of the rod bore. When you find the right cap for its rod you'll see that these marks match up exactly as the hone scored tiny grooves into the metal which continue across the split line into the other half of the assembly. These marks are always unique, rather like a fingerprint, and allow you to match up conrods, main bearing caps and camshaft caps even if you've never seen the engine before and someone else has stripped it down. I have to do this routinely on unknown engines and also as a matter of course on customer jobs to make sure the parts are a correct match before I spend days porting something or building a race engine. When you get the right bits matched together there'll be no offset at the split line that you can feel with a fingernail. If there still is then you need the bores measured for size and ovality by a specialist and possibly modified and rehoned back to as new condition. Share this post Link to post Share on other sites
