Discussion
Just done this!
First you need to make sure the cam followers have no oil in them. Easiest way I found to do this was assemble the valve gear, find TDC on no. 1 and then rotate the crank c/w about 120 degrees. At this point, most of the valves have some lift and the pressure of the valve springs forces the oil out of the followers. If you have new followers, of course, then no problem.
Now you need to find a couple of bits of stiff wire; I used the earth core from some 1.5mm twin & earth cable which is about 54 thou". A single strand from another piece of copper wire was 24 thou". The actual limits are 20 and 60 thou", I just added a bit of a safety margin by using wires that were slightly inside the max. limits.
Rotate the crank so that the follower of the valve you are interested in is on the heel, or 'back' of the cam lobe, i.e. the lowest point. Now fashion your wires into a loop and insert into the followers such that you are measuring the clearance between the top face of the pushrod seat, and the bottom of the retaining circlip. You're looking for a situation where there is not less than the thinner wire, and not more than the thicker wire. You need to check every follower, because, surprise surprise, there WILL be one or two that don't match the rest.
Now remove the valve gear and insert shims between the pedestals and the cylinder head. You can do it by trial and error, or you can get all fancy and work out 'what thickness of shim multiplied by the rocker ratio gives what clearance'. I just tried 3 shim sets and stuck with the set that gave the best results!
I presume, incidentally, that you have actually obtained a set of shims...
You normally get three sets of 8 shims, thicknesses of mine were 16, 33 and 48 thou". About 25 quid a set from Rimmers; however I think they get them from RPI (or t'other way round!) so may be worth checking around for best price. Seems expensive, but cheaper than another engine rebuild if you get it wrong/ cut corners etc...
I rather assumed that my original shim set would be spot on, but it wasn't, and the only thing making any difference would be the new head gaskets. Old and new are composite, so why there'd be 15 thou difference I know not... unless the last person to do the job didn't do it properly, of course... ;-)
W.
First you need to make sure the cam followers have no oil in them. Easiest way I found to do this was assemble the valve gear, find TDC on no. 1 and then rotate the crank c/w about 120 degrees. At this point, most of the valves have some lift and the pressure of the valve springs forces the oil out of the followers. If you have new followers, of course, then no problem.
Now you need to find a couple of bits of stiff wire; I used the earth core from some 1.5mm twin & earth cable which is about 54 thou". A single strand from another piece of copper wire was 24 thou". The actual limits are 20 and 60 thou", I just added a bit of a safety margin by using wires that were slightly inside the max. limits.
Rotate the crank so that the follower of the valve you are interested in is on the heel, or 'back' of the cam lobe, i.e. the lowest point. Now fashion your wires into a loop and insert into the followers such that you are measuring the clearance between the top face of the pushrod seat, and the bottom of the retaining circlip. You're looking for a situation where there is not less than the thinner wire, and not more than the thicker wire. You need to check every follower, because, surprise surprise, there WILL be one or two that don't match the rest.
Now remove the valve gear and insert shims between the pedestals and the cylinder head. You can do it by trial and error, or you can get all fancy and work out 'what thickness of shim multiplied by the rocker ratio gives what clearance'. I just tried 3 shim sets and stuck with the set that gave the best results!
I presume, incidentally, that you have actually obtained a set of shims...
You normally get three sets of 8 shims, thicknesses of mine were 16, 33 and 48 thou". About 25 quid a set from Rimmers; however I think they get them from RPI (or t'other way round!) so may be worth checking around for best price. Seems expensive, but cheaper than another engine rebuild if you get it wrong/ cut corners etc...
I rather assumed that my original shim set would be spot on, but it wasn't, and the only thing making any difference would be the new head gaskets. Old and new are composite, so why there'd be 15 thou difference I know not... unless the last person to do the job didn't do it properly, of course... ;-)
W.
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