7 replies to this topic

[maccers]

My 1275 engine, standard apart from being an SPI now running twin 1.25"su's, has quite worn rocker shaft, and reading another recent post leads me to be believe the face of the rocker where it makes contact is worn too!

I am not after mega bolt on perofrmance, more a smooth running engine. As I have to replace the shaft, posts and rockers, I can buy new standard items, or buy a 1.5 ratio forged set.

Will buying the 1.5 ratio cause any adverse lumpy running, or should I stick with new replacement standard parts? The engine has standard cam and head, valves etc (new valves and new spings - all standard).

[dklawson]

The engine has standard cam and head, valves etc (new valves and new spings - all standard).

It has to be asked. Why were the valves and springs recently replaced while the rocker gear was not?

If you are concerned about wear as well as maintaining a smooth idle, stay with the standard rocker arms, not the 1.5s While the 1.5s will result in valves that open more, they also require more compression of the valve springs which in turn produces higher forces and more wear on the valvetrain components.

[maccers]

They looked ok, but now when its all been put back on with virtually new top end its running rough and after checking play, and visual they are worn.

Just ordered some MED 1.3 ratio rockers with shaft and posts etc as a kit.

[dklawson]

Shaft wear should have been immediately apparent when you looked at the old parts. On the arms both the "hole" and the valve contact pad can wear.

What was worn now that was not apparent before? Is the wear "new" since the valves were redone? I ask because one of the pedestals for the rocker shaft is also the oil feed to the rockershaft. If you put the pedestals on in the wrong position you will starve the rocker arms of oil and there will be very rapid wear. Be sure to check that when you install the new parts.

[bmcecosse]

Generally I am totally against high ratio rockers - but in this case, where you can't easily change the camshaft - the high ratio rockers may be worth having. But as above - they will compress the springs more - so check for coil binding - and they will increase wear on the valve train.

[maccers]

Thanks for your input, I wanted to keep it as much standard as possible, but use decent parts that mean I wont have to be swapping them out after a year. I'll check for the oil way hole with the new parts, I guess the only wear if it was in the wrong way will be on the rocker shaft/rockers and pedestals, ie the bits I am replacing anyway?

[bmcecosse]

Not the pedestals!

[dklawson]

If the oil feed hole for the rocker shaft is blocked by putting the pedestals in the wrong place on the head the wear will show up in the bores of the rocker arms, on the pads of the rocker arms where they contact the valve stems, and on the underneath side of the rocker shaft where the arms pivot. As Roy said, the pedestals themselves will show no signs of wear as they don't move and the shaft doesn't move.