Rockers/Pedestals (pillars) Etc

[Bill_qaz]

Seems a lot of faff and penny pinching by modern suppliers, so they don't have to provide data sheets.
Just like the set of sockets,valve spring wedge, the larger palm wheel and proper wooden storage case.
All of which has gone from the modern version.
Like many modern tools produced to a price
Hence you having to modify yours in your recent post.

If you copy the two charts from my pictures in previous post you have settings for a series.

[svenedin]

Yes. Penny pinching even though the modern tool is rather expensive for what it is. No data sheets due to fear of being sued for inaccurate information perhaps? I always like specialist tools to have a box or storage case rather than rattling around in the bottom of a tool box where they get lost or separated from their instructions.

Stephen

[MikeNash]

A digression perhaps, but all the pictures so far of various rockeries show those springs and washers thigies that press the rockers against the pillars, whether they align with the valve stems or not. It reminds me of what Rob Thomas (of this parish and regarding another piece of Minor design) once said, that its “Amazing that somebody thought it was a good design and no one stopped them”. I had an alignment problem and I think it was M’Learned Friend Phil who pointed me towards the Minispares rocker spacer kit https://www.minispares.com/c-aeg392-roc ... gL3lfD_BwE
It's less that £16 and easier and quicker to use to get alignment than swinging pillars in lathes, MikeN.

[svenedin]

A digression perhaps, but all the pictures so far of various rockeries show those springs and washers thigies that press the rockers against the pillars, whether they align with the valve stems or not. It reminds me of what Rob Thomas (of this parish and regarding another piece of Minor design) once said, that its “Amazing that somebody thought it was a good design and no one stopped them”. I had an alignment problem and I think it was M’Learned Friend Phil who pointed me towards the Minispares rocker spacer kit https://www.minispares.com/c-aeg392-roc ... gL3lfD_BwE
It's less that £16 and easier and quicker to use to get alignment than swinging pillars in lathes, MikeN.

Yes good point and see picture below. I think if you look at that picture that if you wanted perfect alignment, the only way to do so for some of the rockers would be to take material from the side of the pedestal?


Stephen

[svenedin]

Here is a set of sintered rockers showing the contact area that is much wider than it actually has to be and also showing how these wider rockers are tolerant of imprecise alignment.

Out of the 8 rockers only 2 show any signs of actual wear. 6 of the rockers just have a polished area where they has been in contact with the valve stem. 2 have a very slight pit, the edge of which can just be felt with a finger nail. Possibly those 2 valves ran with an incorrect clearance. I know nothing of the engine that these parts came from.

Stephen

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[Bill_qaz]

Could possibly be a valve not rotating or lack of lubrication.

[Pete Bags]

Sintered rocker arms were introduced in 1974 by BL. Mini people don't seem to like the sintered rockers because they have the lowest ratio of all of the variants of 1.21:1 although this is very similar to the original Mini Cooper S forged type which are 1.23:1

Stephen

I had never heard of 'rocker ratios' before reading this thread. I have looked on YouTube to try and understand this (I'm still a bit baffled!)- it seems that changing the rocker ratio could improve the power of the engine. Is this something that can be easily achieved with our engines - simply by fitting a different set of rockers? I'm guessing other components would need changing too?

And does it make a noticeable difference?

Is it worth it?

You would have thought that if BL introduced sintered rocker arms in 1974, then they would have been an improvement (ratio and power wise) from earlier rocker arms, especially as cars were getting heavier!

[svenedin]

Sintered rocker arms were introduced in 1974 by BL. Mini people don't seem to like the sintered rockers because they have the lowest ratio of all of the variants of 1.21:1 although this is very similar to the original Mini Cooper S forged type which are 1.23:1

Stephen

I had never heard of 'rocker ratios' before reading this thread. I have looked on YouTube to try and understand this (I'm still a bit baffled!)- it seems that changing the rocker ratio could improve the power of the engine. Is this something that can be easily achieved with our engines - simply by fitting a different set of rockers? I'm guessing other components would need changing too?

And does it make a noticeable difference?

Is it worth it?

You would have thought that if BL introduced sintered rocker arms in 1974, then they would have been an improvement (ratio and power wise) from earlier rocker arms, especially as cars were getting heavier!

Yes the rocker ratio can be explained as: if the pushrod moves up 1 inch then with a 1.5:1 rocker ratio rocker the valve stem would be pushed down 1.5 inches. Obviously, pushrods do not move such a huge distance but just to explain! So, a higher ratio rocker would open the valve further than a lower ratio rocker all other things staying the same. The different ratios are due to differing geometry of the rockers.

What actual differences this makes is too technical for me but is covered in books such as "Tuning the A-series Engine" by Vizard.

The sintered rockers, the last type, were in use for a very long time. They are very strong, said to be a bit quieter in operation and they don't need to be aligned so carefully.

For a standard A-series engine, I don't think the fact that the sintered rockers have a lower ratio than the other types is of any consequence. The degree the valve opens is not limiting the flow of gases because other factors such as the design of the cylinder head and manifold are already restricting. Also these engines just don't rev high enough for the valve opening to start to have an effect of restricting gas flow. The faster an engine revs, the greater the volume of air in terms of cubic inches per second has to be sucked in and blown out.

The lift of the camshaft is the other major factor in determining how far the valves open. This kind of thing is of interest to those who modify engines for maximum power or torque or whatever which is way beyond my standard plodder Minor. I mentioned the rocker ratios just to be thorough.

So I suspect BL kept the sintered rockers as they were strong and reliable but varied the camshafts instead.

Stephen

[philthehill]

The sintered rocker is much cheaper to produce than the forged or pressed steel rocker.
The ratio of the rocker is related to the lift and opening period of the camshaft.
The rockers fitted to my 1380cc engine are 1.5 ratio with a very high lift camshaft (currently BMC 649 - was Kent Cams 310 scatter profile). I need the 1.5 rockers to make the most of the camshaft. The 649 camshaft was fitted instead of the 310 to bring the power band down as power did not come in until 5500rpm and top revs were in excess of 10,000rpm. Now power comes in at 3500rpm and the engine has a rev limiter set at 7500rpm.
When building the engine I placed a ball of playdough on top of the piston and after fitting the head with a pre used head gasket carefully turned the engine over. Removed the head and checked the clearance as indicated in the playdough. It is most important that the combustion clearance is checked when installing a new camshaft and valve gear especially if the head has been severely skimmed as mine has been to reduce the combustion chamber size which is 19.5cc.
A good read is 'The anatomy of a Mini' which gives details of all the various rocker styles, materials used and ratios with their part numbers.

[Pete Bags]

Thank you Stephen and Phil - every day is a school day!

[svenedin]

You're welcome Pete. For me it is just my nerdy nature and these things interest me. For Phil, it is very important for his performance engines!

Stephen

[svenedin]

Here is a new old stock sintered rocker with its oil paper wrapper.

You can see there is no bush but there is an oil hole to the adjuster screw from the rocker shaft. The blueing shows the rocker tip has been hardened.

Stephen

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[philthehill]

There seems little point in having the drilling from the rocker shaft pivot hole to the rocker adjustment threaded hole as the adjusting screw is not waisted or the adjusting screw drilled hollow.
As I do not have a sintered rocker to hand for examination I will put forward this sinuous and possible explanation.
The threads below the oil transfer hole look to be only half height threads in that the thread peaks are blunted. It could be that oil from the rocker seeps down past the half threads around the ball of the adjustment screw and into the cup of the push rod then on down to the cam follower. It may be that BL found that there was a lack of oil splashing around inside the rocker cover leading to wear of the sintered rocker. BL then decided to install the oil transfer drilling with half height threads in the bottom half of the rocker so that additional oil gets around inside the rocker cover. The threads above the oil transfer drilling look to be full height threads and there are enough threads to support the adjusting screw.
The way the metal is sintered may have an effect on the way the rocker wears. The rocker sintering process allows for the molten hot metal powder to be pressed into a mould so forming the rocker when cooled. The sintering process is a much cheaper way of producing rockers and at that time BL were on their knees and looking for any way to reduce costs.
I will try and obtain more information about these drilled sintered rockers.
Phil

[Bill_qaz]

Interesting theory phil, mine are sintered rocker. The attached picture taken recently clearly shows the pushrod cups are full of oil. So either by drilled rocker or general splash from oil feed to shaft its working. Its also pooled on the pedestal stud so must be quite a lot of splashing.

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[philthehill]

Bill
Thanks for the above.
It is the only solution I can currently come up with.
I am very happy to be advised otherwise.
There has always been plenty of oil flying around inside the 'A' Series rocker cover even without any oil feed to the adjuster end of the rocker.
BL must at one time been confident of sufficient oil to have deleted the oil feed through the rocker to the adjusting screw and on down to the cam follower.
I have no recollection of seeing any oil transfer drilling in the sintered rockers. Saying that the sintered rockers that have come my way have all been destined for the scrap bin. Whilst I use the sintered pillars I always replace the sintered rockers with either forged or very good pressed steel rockers mounted on a thick wall rocker shaft. The sintered rockers are discarded because I do not fully trust the sintered rocker to stay in one piece as I have seen photos and read reports of broken sintered rockers.
I have never had any problems with oil supply to the rockers, push rods or cam followers and I always cast aside the waisted adjuster screws for solid adjustment screws.
Phil

[Bill_qaz]

Phil its very different for you with high performance version. Mines just bog standard recon 1098 when car had 60000 mls and a replacement lead free head @ 90000mls. It still runs good oil pressure and is very gently used. Its currently at 105800mls. So the replacement motor has done 45000mls and the head 15000mls So hopefully will last for a few years/miles to come, with regular oil and filter changes tu1:
Luckily it came with a very comprehensive history file so helps take some of the guess work out of a secondhand buy.

[svenedin]

There seems little point in having the drilling from the rocker shaft pivot hole to the rocker adjustment threaded hole as the adjusting screw is not waisted or the adjusting screw drilled hollow.
As I do not have a sintered rocker to hand for examination I will put forward this sinuous and possible explanation.
The threads below the oil transfer hole look to be only half height threads in that the thread peaks are blunted. It could be that oil from the rocker seeps down past the half threads around the ball of the adjustment screw and into the cup of the push rod then on down to the cam follower. It may be that BL found that there was a lack of oil splashing around inside the rocker cover leading to wear of the sintered rocker. BL then decided to install the oil transfer drilling with half height threads in the bottom half of the rocker so that additional oil gets around inside the rocker cover. The threads above the oil transfer drilling look to be full height threads and there are enough threads to support the adjusting screw.
The way the metal is sintered may have an effect on the way the rocker wears. The rocker sintering process allows for the molten hot metal powder to be pressed into a mould so forming the rocker when cooled. The sintering process is a much cheaper way of producing rockers and at that time BL were on their knees and looking for any way to reduce costs.
I will try and obtain more information about these drilled sintered rockers.
Phil

I'm not sure. The threads for the adjuster screw look all the same. However there is some play if the adjuster screw is wiggled side to side and that only stops when the locknut is tightened. I can't see that any significant quantity of oil would seep down onto the pushrod but I may do a test tomorrow by introducing some oil into the hole in the centre where the rocker spindle would fit. Perhaps the only purpose of this hole is to reduce the risk of the adjuster screw seizing? We all know that does happen.

Stephen