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TR2/3/3A Rocker Pedestal

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CJD

CJD

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I have a stack of rocker shafts, presumably for TR 3's and 4's. Most have aluminum pedestals, but 2 are steel or cast iron. I've been looking through the literature, but cannot find when a change was made, or from which version to which. Can someone fill me in on the difference between the steel and aluminum?
 
Aloha John,

Just happened to be checking out BCF while my TR2/3 factory Service Instruction Manual is within arm's reach (cleaning off the bookshelf). The TR3 supplement says "aluminium" rocker shaft pedestals "were incorporated in normal production at Engine No. TS.12564E." It goes on to explain that the higher degree expansion of the "new metal" allows the same rocker clearance on the exhaust as the inlet, reducing tappet noise when the engine is cold.

Jeff
 
Thanks Jeff...that's what I was looking for. I thought the aluminum was the later version, but the TR2 actually arrived with aluminum, so I was confused. Of course, the TR2 also came fwith a TR4 valve cover, so it looks like the PO used a lot of parts from a donor '4.
 
Oh, and Jeff, It finally sank in when you referred to the "supplement"...I forgot (again) that that was in the back of the manual! Doh. It has a lot of good info that I forget about. Thanks again!
 
I spent all day dis-assembling 6 rocker shafts. I have to be honest, all my prior experience is with stud mounted rockers, so this was a definite learning experience. I always figured rocker shafts were indestructible and that they would last forever. I now know otherwise. Of the 6 shafts, 3 of them had 1/32" grooves worn from the rockers. The springs tend to hide the fact the shaft is worn out, since the springs hold the rockers firmly against the pedestals. I plan to put more force on the rocker in the future, to make sure the wear is taken up when adjusting the valve clearances.

The exhaust rockers tend to wear twice as fast as the intake rockers...not sure why that is. I was lucky enough to have one set of original steel pedestals in the junk pile to put back on the TR2...assuming it ever does get put back together. So, out of 6 complete shafts, I'll have two good assemblies, and one serviceable.

Now on to the thermostat and water pump...
 
John,

You didn't have to replace the rocker shaft on your TR3A? I would consider it a standard replacement part on a TR engine (and probably the same for the bushes) when doing a rebuild. Luckily they are not very expensive ($30.00 right now from TRF).

Scott
 
Hey Scott,

The 3A only had 56k miles. I pulled the rocker shaft and the head, decarboned the chambers, miked the cylinders, and pulled one cap to check the bearing. It was all well within tolerance, so I just buttoned it back up. The shaft looked solid...but that was before I knew how they wear. Next time I check the valve clearances I will pull the 3A shaft and check it again, though.

The mickey mouse Chevy stamped steel rockers mounted on studs are almost bulletproof. I played with changing to roller rockers, but they all failed at a regular rate, while I have only seen a couple stamped rockers ever fail...even with over 100 lbs of seat pressure and 330lbs of open pressure. Looking at the TR rocker shaft, it just appears so much more substantial than the stamped that I figured they would last indefinitely. I now know I am wrong. I think it must be that the rocker shaft is not hardened, whereas the stamped steel rockers are.

I did notice that Moss sells a tuftrided shaft, at a premium, of course. Does anyone have experience with the hardened shaft?
 
I have used them in all the LBC engines I have rebuilt (5 MG's) but have not had a reason to go back and inspect one for ware. I don't think I have ever seen an original shaft that did not need replacing in these cars. The one in my 60 TR 3 will have to be replaced.
 
Final update on my pedestal project.

It turned out that, out of 6 shafts, only one was reusable. The other two that looked good when still dirty were, in fact, bad in just one or two locations each. They will come in handy as my newest drift punches, though. So, for all working on their rocker pedestals in the future, plan on replacing the shaft on every rebuild, like Scott pointed out!

I am still curious about the Moss tuftrided shaft. The bronze bushings in the rockers seem to last many times longer than the shaft, so a decent hardened shaft would be a good investment for anyone planning to put mileage on their car. If I end up replacing the one in the TR3, it will be with the hardened shaft. It runs a bit more than double the cost of the standard shaft.

Moving on the to water pump...
 
yeh I wondered about that also; the shafts I have seen wouldwear out and yet many of the rockers still had good brass
 
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