On MINI and BMW valvetronic engines, the rocker arms (roller drag lever) and the intermediate levers are graded from 1-5; each has a different part number.


Item 8 is pictured here.


My question is; what do those different part numbers represent in term of dimensions?

Even the INA (the OEM supplier to BMW and MINI) literature doesn't tell me. I need a little more valve lift on cylinder 2 to fix an idle misfire problem.

 

This link has the entire text associated with the picture/image you posted.

https://www.partinfo.co.uk/files/INA%200040.pdf

However, it provides no details on the differences.

You might email or call the parts supplier company listed in the PDF and ask what the differences are.

 

Yep ... had the link. You're assuming I didn't already try contacting IDA.

I guess nobody really knows.

 

All I can go by is what you posted.

I rebuilt a Datsun (before it was Nissan) 1.6l SOHC engine. Each cam lobe pressed against a rocker and specifically a rocker pad. I took the head to a head shop which was highly regarded. My research found the cam lobe contact should be centered on the rocker pad. I believe this required removing a bit of metal from the end of the valve stem. (The valve stems could stick up higher from metal being removed from the valve seats and the valve sealing surfaces.) I brought this to the attention of the head shop manager. He was unaware this but thanked me for the info and said he'd see the contact patches were right.

When I got the head back I checked each lobe/rocker pad contact and every one was centered.

I sort of suspect the different rocker arms are for use in getting the cam lobe contact patch centered. At the factory during assembly either by some measurement or even trial and error a suitable rocker arm is selected. But how you would handle this in your garage...