Normal Oil Pressure

[JimVillers]

Peter .... Thanks; I'll visit my machinist tomorrow to decide on a repair plan.  I'll update your when I learn something.

[JimVillers]

Peter ..... It looks like you were spot on.  The cam bearings were VERY loose, .005-.007 or so.  I attached the specifications which show it should have about .001 clearance for the oil film. 

It was good that I pulled the engine, the bearings were already showing some wear from metal-to-metal contact. 

I'll post the fix when my machinist decides on what he will do.

[PeterL]

Glad I could help.  I am a Reliability Engineer, essentially my whole job is to systematically pick apart things to find out how/why they failed and how to eliminate that mode of failure.  I did not want to pull my engine this summer and not know what I was getting into, so I thought long and hard since October about what the problem could be.  I am glad that you have confirmed the problem.
Again, there are a bunch of different ways to repair it. I myself like simple/straight forward approaches.  I strongly feel that cast iron sleeves shrunk in with Liquid Nitrogen are the best most cost effective solution.  Keep in mind yes, for years and years interference bushings were pounded in with a hammer but, liquid nitrogen will keep the fit concentric and ensures you that the oil port will line up exactly where it needs to go.  Oh and one last thing, you can get one hell of an interference fit (they will never come loose EVER).

 Keep me informed on what they do for the repair!

Peter

[JimVillers]

Peter ..... Just to provide an update.� We first tried a new cam shaft to see if that might provide a solution.� It picked up a thousandth or two but not enough t get close to the specification.� The block is being sent to another shop to have the journals bored and bronze bushings installed.� They are using bronze because that is what they are familiar with and what they used on a similar jobs on old Triumph engine.

[PeterL]

Cool beans, if they have a history of that type of repair I am all for it.  I only made my recommendations on the basis that the machine shop had not made a similar repair before. 

Good luck!!

[JimVillers]

Peter .... I have great confidence in the shop.  They normally work on vintage race engines but also do the one off type of stuff that we hobbyist drag in.  They have all of the fancy stuff like a flow bench for tuning the head to a stationary dyno to run and tune engines before installing them into the car.  There is just not time on the track to break in an engine.

[JimVillers]

Six weeks later and I am still waiting for my block to be repaired.  When it left the "in waiting" area, the machinist changed his approach.  He felt that since the holes in the block were very round, he decided to do the machining on the camshaft.  He ground down the cam bearings, sleeved the cam bearings to increase their size and then grind down the cam bearings to fit the block.  He said that it was easier to accurately ground down the cam to fit the block than bush the block to fit the cam. 

As you said, there are several approaches to solve the problem.  I'll report oil pressure when the engine is assembled and running.

[PeterL]

If the bores are indeed round as he said, sleeving and grinding is pretty normal.  Honestly, whats not normal is for the housing (cam bores) to be "round" if they are worn.  Let me know how it works out!