Hi,
Could someone say if there are any preferences in using short or long tappet location plates.
Also to locate the barrel I have discovered that there are 2 studs reduced to accept smaller nuts that I believe go to the front of the engine 1 each side of centre, could someone say if this is important and why it is done.
Many thanks jim.
650 Engine rebuild
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650 Rebuild
The longer location plates were used on the early engines until the pressure fed rockers arrived in the 1960s. Shorter plates were then used to allow the oil from the head to drain past the followers more easily.
The two reduced barrel studs are located over the shoulders of the camshaft tunnel. In this position the loading on them does not go immediatly down vertically to the crankcase sides. This in turn causes stress on the shoulders so reduced size nuts are used to limited any vertical force when they were torqued up.
The left side in particular was very prone to cracking just below the stud on high performance engines. An issue that caught out the Norton Racing Team one year at the Thruxton 500 mile event.
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Rebuilding a 650 engiine
Hi Robert, I appreciate that this doesn't answer your original question, but I would just like to comment on the issue of rotating rocker shafts.
Rocker shafts are a light interference fit in the cylinder head and at working temperature they become loose and capable of movement .
Most rocker shafts are fitted as per the " book" this restricts the flow of oil into the rocker but increases the pressure in the shaft , it is now possible for the shaft to move inwards and become dislocated from the ears on the cover plate.
Once this happens the shaft can rotate and cut the oil feed off.
I always check the inward movement of the shaft ( which could be in excess of 060") and then fit packing spacers to bring the end of the shaft flush with the outer face of the c/head.
Having done this it is then unnecessary to buy plates with longer ears.
I also turn the rocker shafts round the right way, but I don't expect many people will take that bit of advice.
Good luck with the rebuild.
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Hi Robert
Did you mean long or short rocker shaft locking plates? If so, I used the long ones as I understand that they locate the shafts better to stop them rotating and losing the lubrication to the rocker arms.
The reduced studs would make it easier to get a spanner/socket onto the nuts, but I didn't have a problem using a ring key on mine, although I've got no idea what actual torque is applied to them - they are just 'tight'!
Good luck with the rebuild.
Kevin