MGB Register Forum

I've had the head skimmed on the B (1976 model) and in re-assembling I've come across a query regarding the rocker arms.

With the head bolted (torqued) down and the rocker assembly fitted, on certain valves the rocker can be rocked by about 1/4" to the point it clears the push rod completely and I can then wiggle that around and lift it in it's bore. As I rotate the engine this closes the gap but then frees other rockers to a similar extent.

Unfortunately my car and Haynes manual are in dad's garage 60 miles from where I type this so I can't look it up or show pictures on here but it feels wrong to me, the push rod could miss the rocker and jam between the bore and the ball of the rocker from what I can see. I just want to know what to look for when I get there on Saturday.

I haven't yet adjusted the tappets but it seems to be a lot of adjustment needed, I'm not sure how they were when I took the head off unfortunately and I've put everything back in the same order as far as I can tell.

The engine is pretty old and worn so I'm not expecting miracles I just don't want to blow it up!

Afternoon Tom.
Adjust the tappets and then see what it's like. 3 years ago I had the head on my 1977 BGT "Downtoniized" by Downton Engineering's former ace cylinder head man. He fitted MGC inlet valves and reassured me there would be ample adjustment despite the extra length of the valves and he was right.
Strange that there appears to be excessive movement when skimming the head would bring the pushrods closer to the rocker arms.
. Vic Butler

A small aside to the matter of rocker arms and tappet clearances. On a recent MGB Register event I was having trouble with very lumpy idling. After a bit of thought I decided this might be down to valve seat recession allowing the valves to seat deeper into the head and take up the tappet clearance. When I removed the rocker cover I discovered there was no clearance at all on all 8 valves. Now the clearances are re-set as per handbook the engine is running sweetly again and I just hope no exhaust valves have suffered from burns.
Goes to show that even at normal operating speeds the lack of lead in the fuel does eventually have an effect. I have not tried using additives up to this point but may consider putting some in the tank from now on if only to avoid the chore of re-setting tappet clearances.