Rockers question

[Rich997]

Hi picked up a set described as 'Formula Junior', would be interested if anyone can identify them.
Photo below, 2A534 forged and have MS under the part number, which might be a certain well known company of course, but their current forged rockers don't have the square ends.

Second image shows one of a set described to me as 'Special Tuning' which I've not seen elsewhere. Can anyone identify this forging?

[smithyrc30]

Second picture is the original A series cast rocker arm.

It is not forged (cold chilled cast Iron) and does break (usually right behind the valve tip pad) if you have high load springs or use over 6000rpm regularly.

In days of old when there were old Minors and A35's etc. in scrap yards you would see loads of them, usually on assemblies with aluminum rocker posts.

The tips are only cold chilled so once this has worn through the valve tip eats its way through the soft material below with amazing rapidity.

They are about as low cost/performance as you can get and definitely not a performance add on.

The pressed steel ones are much better.

The upper one looks like the original Mini Spares copy of the Cooper S part. I don't recall accurately but I think these came in 1.3 and 1.5 ratios.

[mk1]

I have had a set of the ones above, they were 1.5 : 1 but I have no idea on the original manufacturer.

M

[Toby]

The 2A534 rockers are indeed regarded as the Formula Junior rockers as they were used on the 948 engines and 1071 engines. They will also line up differently with valves than the later ones.

The lightened rocker looks like the later type which was supplied by BMC. These were basically regular forged rockers which were had a significant amount shaved off they were usually fitted with solid spacers in between the rockers and re-branded as the special tuning item.

In the below example you can still make out the original part number on one of them, yet usually that got ground off.

[mk1]

The "top" ones aren't BMC rockers. The shape is SIGNIFICANTLY different to any BMC one & the quality of the castingh is a bit rough when compared to any BMC item.

M

[Toby]

Just to be clear, I wasn't implying that the "top" rockers which were posted are BMC ones, they are similar. As Mark states the casting is too rough on them.

[smithyrc30]

The 2A534 rockers are indeed regarded as the Formula Junior rockers as they were used on the 948 engines and 1071 engines. They will also line up differently with valves than the later ones.

The lightened rocker looks like the later type which was supplied by BMC. These were basically regular forged rockers which were had a significant amount shaved off they were usually fitted with solid spacers in between the rockers and re-branded as the special tuning item.

In the below example you can still make out the original part number on one of them, yet usually that got ground off.

The rocker arms in the picture posted above are the forged items, the ones in the original are not. You can see by the shape of the valve end, on the cast ones the side view is of a trapezoid covering the whole 'pad' area. The forged steel ones (formula junior, S etc.) have a smaller head which shows the 'beam' of the arm going into the valve tip end and the end of the beam rolling over into the radius on the valve pad.

I've broken the ones shown in the original picture just by using more than 6000rpm.

[Rich997]

Interesting comments.

The other 8 rockers I have in the set have similar patina to Toby's
Although a couple have wear on the pads, I presume they will be serviceable if dressed.
On that note I purchased a set of 'S' forged rockers from MS which seem to be good quality, but did need plenty of polishing / finishing.

[smithyrc30]

Interesting comments.

The other 8 rockers I have in the set have similar patina to Toby's
Although a couple have wear on the pads, I presume they will be serviceable if dressed.
On that note I purchased a set of 'S' forged rockers from MS which seem to be good quality, but did need plenty of polishing / finishing.

Good luck with that. When they break, the hammer shaped tip comes adrift which stops the cylinder running. Trouble is the bit goes around in the rocker cover (denting it) and then if you are lucky drops somewhere it won't damage anything. However it can get stuck into the coils of the valve springs next to it which then breaks the spring and drops the valve into the chamber and thence the piston.... All this happens while the driver is still registering that the engine has a sudden misfire. Today with mobile phones it is just an inconvenience and expense. In the early 1980's when there were no mobile phones to speak of and it is cold, raining and dark in the middle of the night 4 miles into a muddy rally stage and you are 40 miles from home you tend to express some disapprobation at their use.

As you can see from the picture, the radius on the pad extends into the strengthening beam that runs to the pivot. This is where they break. Usually from the end of the machined surface where the stress is highest. If you re-machine the radius then you have to cut into the beam which puts a huge stress riser there and they snap.

Vizard mentions in his books that even the S forged rockers should not be touched in this region.

As mentioned previously they are cold chilled to harden them on the tips (the sintered A+ ones are the same) and once through this layer they are very soft compared to the valve. You would have to re-harden them if the pad is worn.

[Spitz]

I interested to hear the outcome of the OP....any update?

[Toby]

Here is the part of a page of a June 63 parts list for the Cooper and S. As you can see both the pressed steel and the upgrade for the S are listed.

S rockers are quite a can of worms, because there are quite a few different types which were produced and used during the production run of the S. I can only imagine that this was done as improvements were being made in quality.

https://picasaweb.google.com/m/viewer#p ... 6460588802