Rocker shaft assembly for a 1275 S

[Andrew1967]

Looking at rebuilding the rocker shaft assembly for HOY today and took the old one apart ..

I'm not entirely sure it is correct

Please see the pics - I've laid it out exactly as I disassembled it.

Should there be a spring washer at either end, between the outer plain washer and the outer rockers ?

There is a plain washer between each exhaust rocker and pedestal . The parts manual only refers to one 'piece - distance - exhaust rocker to bracket' (AEG168), No 78 on page MA56 of AKD3509

Should the pedestals be steel on a 65 S ?

[iain1967s]

No spring washers on the original [used] 12G1221 set that I bought for my 1275 S engine. Just a combination of 10 and 40 thou spacer washers to take up the gap between the end rocker and the split pin.

[Andrew1967]

Interesting Iain, that what these seem to be ... maybe its correct ?

Any washers between the exhaust rockers and pedestals ?

They are (barring one) the original S type rockers but are worn and I have some NOS 1221's to fit.

Anyone else able to chip in ?

[iain1967s]

There are an apparently random number of spacers fitted between rockers and pedestals. Not all rockers have them, and from a quick look it appears to have been done in order to center the rocker on the pushrod so that it’s vertical, with little interest where the stem of the valve stem meets the foot pad of the rocker.

As I’m using a Mk3 940 head rather than a Mk1 163, it’s possible the valve guides are spaced on a slightly different pitch, but from the wear pattern on the pads I’d say it was like that from day 1 on the original install too.

Here’s a close-up for each rocker, you can see the spacers clearly if you zoom in.

[Andrew1967]

That's very useful Iain, thank you.

I too am using a 12g940 '1805' head on HOY, unable to find a decent 163.

I'll reassemble as it came apart, with the new shaft and rockers, and will look carefully at how it all sits before tightening it all down.

I have a couple of other rocker assemblies here, and they have no spacers at all !

[croc7]

It is my understanding that the primary function of washers/spacers/shims is to center the push rods in the holes. The pads on the rockers are intentionally wide to compensate for any misalignment over the valve stems. To reduce side load on the rocker shaft and bushings, having the rocker pads centered over the valve stems would be ideal, but would involve machining of the pedestals, rockers, etc. and probably not necessary for a road car. I chased my tail, changing washers and shims trying to get everything 'just so' until I surrendered to the fact that it wasn't going to happen and found a happy medium between the two.

[Toby]

Andrew, you ought to have a spring washer and a plain washer on each end of the shaft. The regular washer sits on the outside. The other rings next to some of the rockers are shims, these were fitted to align the rockers with the valve stems. They come in two thicknesses, AEG 169 and AEG 168 and you can fit them as required. And the pedestals should indeed be steel

[Andrew1967]

Many thanks Ian, Croc and Toby

I can get a couple of the spring type washers off a pressed rocker assembly I have here and will see how it all lines up fitting it back as it came apart and adjust accordingly.

The engine was original built for a bit of abuse so hopefully the rockers were set up accordingly. Having said that, as I'm using NOS rockers they may need altering any way.

[Exminiman]

…….thread resurrection , but off on a tangent…:)

Might be wrong, but didn’t ST supply a set of rockers with solid spacers back in the day?

Just wondering whether the rockers with solid spacers were centred over push rod or valve stem, can see an argument for either.

[trevorhp]

There were also 'nylotron/nylatron' solid spacers available back in the day -60's /70's from memory.
T

[Polarsilver]

1275 S Rockers.jpg

[Spider]

…….thread resurrection , but off on a tangent…:)

Might be wrong, but didn’t ST supply a set of rockers with solid spacers back in the day?

Just wondering whether the rockers with solid spacers were centred over push rod or valve stem, can see an argument for either.

ST did list C-AEG392 as Rocker Spacers. That's from a late list, but checking on an earlier listing, they didn't have them, so I'm not sure when they introduced them.

The Rockers were closer to the Push Rod (and Tappet) Centre, with the Valve Stems, particularly in the 1275's, off-set.

[AndyPen]

…….thread resurrection , but off on a tangent…:)

Might be wrong, but didn’t ST supply a set of rockers with solid spacers back in the day?

Just wondering whether the rockers with solid spacers were centred over push rod or valve stem, can see an argument for either.

I'm sure I still have a set with those somewhere - may have a nose after Christmas

[Exminiman]

Thanks for photo Norman, looks like they are centred over the pushrods ?

[Polarsilver]

The Photo of my 1293 engine was built with the third series "S" block & this engine ran very well with solid rocker spacers aligned to vertical Push Rods .
(now a spare as i swapped over this engine & gearbox for a correct to my car 1070 engine & box )