9 replies to this topic

[A1111j]

Hi everyone I have recently bought a 1971 mini. I have noticed I have roller rockers on the car and then had a look at the timing chain setup and I cant find anything like it online. I was wonder if you guys can help me with this and if some one can advice me on what my valve clearances should be? I am going to attach the photos iv taken.

This is what I know about the car it has a 1275 head with weber dcoe40 and Kent cam 544.

Attached Files

•  20200809_113602_resized.jpg   56.66K   3 downloads
•  20200809_113553_resized.jpg   59.84K   4 downloads
•  20200808_092405_resized.jpg   33.85K   6 downloads
•  20200808_092304_resized.jpg   57.77K   3 downloads

[nicklouse]

is there anything stamped on the end of the camshaft?

 

ok 544  16 thou

Edited by nicklouse, 09 August 2020 - 12:52 PM.

[imack]

I've not seen a multi plate chain and timing gear on an A series before. Nice.

[GraemeC]

Think it is a Kent ‘Silent Chain’ set up - as far as I know they’re now NLA for the A series

[nicklouse]

Think it is a Kent ‘Silent Chain’ set up - as far as I know they’re now NLA for the A series

The gear set does look like my Kent set up. But without the chain.

[A1111j]

Thanks guys is that 16thou inlet and exhaust?

[Cooperman]

The original BMC Special Tuning data sheet gave the valve clearances as 12 thou for the 544. I have set that when I have used a 544 with no issues.

[A1111j]

Is that with the roller rockers or it doesn't make a difference?

[GraemeC]

You’d normally increase the clearance for higher ratio rockers:

12 thou / 1.2 * 1.5 = 15 thou.   (not perfect as the standard rockers aren’t exactly 1.2:1)

 

However we are ASSUMING that you roller tip rockers are 1.5:1 ratio - chances are they are, in fact they look like early MED ones.

[Cooperman]

the lift of the rockers nmakes no real difference as the gap it there to ensure that as the valves expand due to the heat, there will still be a gap so that the valves will always close.

The only other thing is that the tighter the valve gap the longer the valves stay open. It is only a slight amount and most people ignore it.

On my 1275 'S' I have a 286 cam and 1.5 rockers and I set to 12 thou. Never had any issues.