Rocker shaft diameter

[dalgrae]

I intend to refurbish the rocker shaft and fit new bushes to the rockers on my car and note from previous posts that the bushes when assembled to the rockers need reaming , does anyone please know the diameter of the reamer required so I can check I have the correct size

[IslipMinor]

The rocker shaft diameter is 9/16" or 0.5625".

[bmcecosse]

Nearly all the wear will be in the shaft - not the rocker bushes. So you could try a new shaft without worrying about the bushes...

[dalgrae]

Thanks for the info ,I have bought a new shaft for less than £10 and the bushes are only £1.50 each so I have ordererd these as well, I have found a 9/16 reamer so the whole job should be done for less than £25 which is a lot less than the rocker shaft exchange price some dealers are asking

[bmcecosse]

Do test the rockers on the shaft before deciding if the bushes are worn enougfh to justify the hard work! And of course - amke sure you assemble the rockers correctly - to let the oil up into the hollow shaft.........

[dalgrae]

I have taken the parts off the car and the rocker shaft is worn on the middle rocker diameters with the bushes in the rockers also worn so at the least these will be replaced , but thanks anyway for the advice

[bmcecosse]

Odd it would only be those two! Let's see some pictures before and after if you can?

[dalgrae]

More advice please BMC after deciding to do more checks how much oil is supplied to the rocker shaft ,when I took the rocker cover off there was not much oil at all present ,although when I stripped the shaft down some oil was inside the shaft but not a lot.I decided to crank the engine over with the rocker shaft off the engine ,I had 40 psi plus on the gauge but no sign of oil coming from the oil feed hole in the top front of the cylinder head this process was done several times.Using a stiff piece of wire I thought it would pass all the way through the head and carry on down toward the front camshaft bearing as the manual shows this is where the oil supply comes from but the wire would not do this it actualy stopped about 1/4"short on the cylinder head depth .so before I take off the head, do the holes in the head and block line up or is there something I am missing on my 948 cc engine

[bmcecosse]

No - they don't line up. If you look at the front of the head you will see a rivet/plug where a horizontal drilling that joins the flow from the block to the vertical passage to the rocker pillar. This is the passage that can become exposed if too much is skimmed off the head. With 40 psi I would have expected a good flow if not exactly a 'jet' of oil from the head...although I confess it's not a test I have ever done. You may need to pop the head to check the passage. But you will be doing that anyway to fit a new head gasket - since you have released the nuts holding down the rocker pillars! Or -did you just slide the rocker shaft out, without loosening the head nuts???

[dalgrae]

Thanks I knew you would have the answer and yes I did release all the nuts so I will now change the gasket .I have put compressed air at about 50 psi onto the hole in the cylinder head and it appears to be clear , as with one of my old Triumph bikes I am taking the opportunity to remove the 3 off springs from the rocker shaft and replace with machined spacers this should take away any sideways load on the rockers, it certainly worked on the Triumph so I do not see why it would be any different on the car engine

[bmcecosse]

The spacers can be added - and are done on performance engines to accurately align the rockers, but negligible advantage on a standard engine.

[dalgrae]

Thanks for info I am not looking for any advantage but a better engineering solution I feel that the spring arrangement is for cost purposes to take up production tolerences ,and as they only tool less than 15 minutes to make the spacers it makes me happy to fit them I will attempt to post a photo of the completed assembly

[philthehill]

The spacers mentioned used to be available from BL Special Tuning Part No: C-AEG397. They still needed shiming to get the rocker central over the valve stem but if you have access to a lathe you may be able to make up individual spacers to suit.

[dalgrae]

Thanks for the info and yes I have my own lathe, with the rocker shaft still on the engine I accurately measured the gaps then I have replicated these dimensions with the spacers and will finally adjust when back on the engine if required