Worn rocker shafts?

[bealo]

Hi guys,
Can anyone tell me what is considered normal wearing s rocker shaft??

On dismantling the head from my m20b20 engine I’ve noticed that where the rocker arms sit on the shaft there is scoring to the shaft that you can feel with your finger with ease.

Is this normal wear or should I be looking at replacing the shafts?

Cheers Iain

[e21Keith]

Just been through the same process myself.

I could feel wear on the shafts and concluded that there would also wear in the rockers themselves. Luckily I had a second head and there was no apparent wear on the corresponding parts so I just swapped them all over to my head.

What I have also noticed is that at higher mileage there was also wear to the rockers where they contact the camshaft so also worth a look.

[bealo]

Thanks for the reply

The rockers actually don’t look or feel that bad inside and where the touch the cam

It’s just the shafts so wondered if it’s normal?

[BertjeConti]

Rocker shafts should not show wear at all, a scored surface is not good, and, if so, the rocker arms will be worn too.
I think that head had a lubrication problem or neglected oil changes.

[bealo]

I’ve never heard/seen the engine running but before stripping it was VERY seized!!!

Basically I bought a lemon!!! Or a good set weight!

Are thinking new shafts and rockers? Or could they be salvaged?

This is my first engine rebuild so excuse my inexperienced questions!!

[uwbuurman]

This is my first engine rebuild so excuse my inexperienced questions!!

Let's disregard this comment and agree that there are no stupid questions. Just ask!!! Others learn from this q&a aswell.

[e21Keith]

If you say the engine you bought is seized then I think I'd concentrate on the bottom end first as there is no point spending money on the head if you would be better replacing the entire engine.

Coming back to the rockers and shafts you're probably best to replace but new can be very expensive. I have a 323i but I've used the valve gear from a low mileage 325i head as the parts are the same on all M20s (as far as I know).

I actually have a complete 65k mile M20 320 carb engine from an '81 e21 320 sitting in my garage which I may be willing to sell, please PM me if you're interested?

[bealo]

Hi Keith,

The bottom end is pretty much done, fully stripped and cleaned and painted New piston rings and shells all new gaskets/seals new water pump and stat. The carb has been stumped and serviced just the head to do and it it all together

I’m a little bit committed to this engine now

I do have another m20b20 but it’s sat in the car for years with no bonnet and no sump! Might be worth a look at the head though

[e21Keith]

OK, whatever head you decide to use it's worth thinking about crack testing as the original "200" casting is very prone to cracks under the camshaft, one of mine had a crack end-to-end through the camshaft bearings.

[bealo]

Ok thanks for the advise

[bealo]

Finally took the head off the other engine and to my surprise it looks a lot cleaner

Any tips on removing the shafts ??

I’ve loosened the eccentrics and have rocker 6 on full lift, I can move the shaft by hand but really struggle to get the rockers off the shaft

I’m removing the exhaust side first and have the first two rockers off but then disaster I’ve been using a drift to gently knock the shaft out but this causes the rocker to hit the rocker on the other side and has damaged it

[BertjeConti]

Shift the free/lose rockers aside and then turn the camshaft to free the remaining rockers.
Pull the shaft only when all rockers are free/lose.

[bealo]

That part of it is fine but it’s when it comes to sliding the rocker of the end of the shaft it seems really tight and I cannot remove by hand

The rockers will slide along the shaft freely but not off the end