Oil cooled rocker shafts


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By pcmenten - 17 Years Ago
I was thinking about stiffening a rocker shaft by having them made like the gun barrel of a 22 caliber rifle so that it would have thicker walls but still have an oil passage. It was just idle musing because I don't ever expect to get into competition engine work on a y-block.



I was considering the issue of pressurization of the rocker shaft oil, air entrapment, etc. when it occurred to me that the overflow design of the rocker shaft might have been an effort to oil cool the shaft itself, so higher volumes of oil through the rocker shaft might be a deliberate design element.



Of course, some of the rockers won't get the oil flowing through the rocker shaft that the rest are getting, but 3/4 of the rockers do get the full flow.



Just random thoughts.
By Ted - 17 Years Ago

The shafts on my roadster’s Y engine are as you are currently contemplating as they are thick walled with a much smaller thru hole for oiling.  They were done in this manner to increase the overall strength of the shaft and reduce any potential for flex so I could run valve springs that would both handle 0.595” at the valve and buzz the engine up to 7200 rpms.  The material that was used was already sized and hardened correctly on the O.D. which alleviated the concern about using a non-hardened material in such a high pressure environment.  After several years of use, these shafts are still holding up fine with no observable wear taking place but it is a race engine with only a ¼ mile at a time being put on them.

 

For the most part, the stock shafts are more than adequate in most applications but Verne Shumann now offers rocker shafts for the Y which have all the performance enhancements that were originally specified by Holman & Moody.  The overall finish on Verne’s new rocker shafts is completely different which makes them easily discernable from the run of the mill shafts that are currently available.

By mctim64 - 17 Years Ago
[quote]pcmenten (12/23/2008)


I was considering the issue of pressurization of the rocker shaft oil, air entrapment, etc. when it occurred to me that the overflow design of the rocker shaft might have been an effort to oil cool the shaft itself, so higher volumes of oil through the rocker shaft might be a deliberate design element.

quote]

I have been pressurizing the rockers for years when it was brought to my attention that air may be trapped without the overflow. I still modify the rockers the way I used to with the addition of a small airbleed in the last tower.  After looking at some of the old ones I had modified I see that the bolt that is used to center the shaft is lose enough in the hole, that is also chamfered, that the air has been bleeding off all along.