420 C, No Oil To Top

[yukonjack]

My crawler had its center frame replaced in some prior life so the S/N tag has been lost, but it was sold to me several years ago as an early model 420. I pulled the valve cover earlier this week, and found there is no oil flowing up to the rocker arm assembly. After removing the external tube to the head and the fitting out of the block, found there is no oil from the port in the right rear of the block. I had a wire in there as far as it would go and the passage is clean. The original oil pressure gauge is still screwed into the filter housing and reads "Normal" when operating.

I have Section 100 of the Model 40 service manual in addition to the 420 manual, which says lubrication is part pressure and part splash...which bearings are splash lubricated? I know the rocker arms were starving for oil, and wondering if the rear main and/or cam bearings may have been oil starved as well? The artist's rendition of the engine cutaway in the service manual was unclear; is the pressurized oil supply carried in tubing in the crankcase that might have broken from vibration, or in drilled passageways that might be plugged somewhere?

Thanks for any enlightenment anyone can offer; it will help me to decide if I will tear into it, or offer it for sale as a parts machine (that at least runs well enough to load itself on a trailer).

Regards from Atlantic Canada, Jack Murray

[fundytides]

Hi Jack,
I think it is the same as my Model 40. If so, someone may have put the wrong rear stud in the rocker arm assembly. The rear stud has a flat on it to carry oil from the passage in the head, fed by the outside oil line, to the rocker shaft. If a previous owner had the head/rocker shaft off, he may have put the wrong stud in the wrong end of the rocker shaft. Easy mistake to make if you don't know about it. Dave

[Lavoy]

I would echo what Dave said. If it is not that, I would question whether someone put the back cam bushing in wrong.
Keep in mind, there is never a "flow" of oil there, but it is a steady pulse that will eventually get into the rockershaft.
Lavoy

[yukonjack]

Thanks...its too nice a day to be in the shop today, but next shop day I'll pull that rear stud to see if they got mixed up. I'll let everyone know what I find. Jack

[yukonjack]

I would echo what Dave said. If it is not that, I would question whether someone put the back cam bushing in wrong.
Keep in mind, there is never a "flow" of oil there, but it is a steady pulse that will eventually get into the rockershaft.
Lavoy

Well, I had an afternoon last week to tinker in the shop...

The correct stud was in the rear of the head...but there has been no oil to the rocker assembly in a long time, perhaps since the last time the engine was freshened up (before I owned it) since the rockershaft (M3287T) and rocker arms (AM2847T & AM2845T) are REALLY trashed from wear. With the external oil line removed, no oil pulses out of the port in the block; so perhaps, as Lavoy suggested, the cam bearing was installed wrong back then.

My plan now is to put the old girl back together using the old parts, back it out of the shop to drop the blade off, then turn it around and back in so I can have better access with the engine hoist. After the snow flies I'll dig into it to see what I've got; once I get to the root problem then I'll start trying to source parts.

Stay tuned... Jack

[Lavoy]

My bet is cam bushing in wrong then.
Lavoy

[fundytides]

Lavoy is probably right. I certainly wouldn't bet against him. Thanks for keeping us updated Jack and let us know what you eventually find. We all learn from the collective experience. Also, thanks to Lavoy for establishing and maintaining this great forum. I was a newbie when I bought my 40c several years ago and needed all the help I could get (still do on occasion). Good luck Jack!