Getting a set of 906's prepped and have found one of them to have cracks down through the rocker shaft pedestal. Is this a common place for these to crack? These came off a 500 CI 440 that hadn't run much. It has roller rockers and was running a mild street cam. Nothing real wild in this engine, is there something I should be look at that might have caused this. I have no history on how this engine was run, new owner bought the car as non running and brought me the engine.


Thanks
Dan

I've seen a lot of the 906 crack externally (freeze cracks probally) under the center two exhaust ports but I have not seen what you have I would think that maybe somebody use to long of fasteners on the rocker arm shafts bottoming them out and then overtighten them to boot what else is wrong with it so far?

Cab, the engine was apart when I received it. It looked like a lot of dirt went through it by the looks of the piston skirts, and bearings. It has a 440 source crank with a full radius, but the main bearings were not chamfered. The rod bearings were. Both the rod and main bearings are very shiny at the outer edge towards the chamfer, and also show to be very shiny in other places. I will use the chamfered mains on the rebuild. Any thoughts on why they look this way?

I will have to check out the rocker shaft bolts.








Thanks
Dan

Yep seen this a lot. someone try to shim the shafts up. use to be a old trick. they did make shims for this. but a lot of guys use what ever they had..

I would look at the rod side clearnances and then the crankshaft end play(thrust clearances) to see if they are to tight on the rods and to much thrust on the mains, if no on either then it is time to get the bering scraper out and gently increase the raduis on both Are those Clevite bearings on both? If so you might want to switch to the Federal Mogul race bearings, I lie and use there 440 truck narrow full groove main bearings # 4095 and the BB Chevy rod bearings 7200CH with no hole in the bottom half for the alignment dowel in aluminum rods like yours have