MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Tappet adjustment

I do remember reading somewhere about an alternative method of adjusting the tappets without using feeler gauges. It was by screwing down the tappet/rocker arm until there was no clearance, then backing off the screw by a certain amount to get the right clearance. I have a feeling it was by about two and a half turns but would appreciate it if this could be confirmed by others.
Evidently this method eliminates the problem with worn rocker heads.
Trevor Harvey

There's a device made by gunsons called the "Click-Adjust" which works like that - basically, each "click" backs the screw off by a set amount so you tighten it up and count the clicks as you back it off to set the right clearance. I have one and it seems to work well enough!

Cheers,
Tim
T Jenner

Feelers and the "Rule of Nine" does it for me, slow and long winded but it works..
K Harris

From what I remember, you back it off by a quarter of a turn.
Geoff Everitt

I always work by the rule of nine. Can anyone confirm that as Geoff sugests its by a quarter of a turn.
Thanks Trev
Trevor Harvey

By calculation,

1 revolution of the screw = 360 deg, which is = to the pitch of the screw. Therefore the gap (G) = 360xG degrees of rotation.
The trick is to get the rotation within about 5 deg.
Never tried this method, but it makes since to give it a bash next time.

Richard
RH Davidson

Oops,

G = 360xG/P

Richard.
RH Davidson

So, what's the pitch of the screw then? Without that it's a non-starter.
Paul Hunt

Oh, and it is a damn sight easier to check the gap with feeler gauges and find they are spot-on and leave them be, than to upset the gap by altering the screw and lock-nut to reset them every time. I've not had to change mine in years. It also wears out the threads.
Paul Hunt

As well as the pitch of the thread, the lengths of the rocker arm either side of the pivot need to be considered when making the calculation. My recollection is that a quarter of a turn was actually 14.6 thou (but I'm not 100% sure).
Geoff Everitt

Yep but if you have a Piper 270 etc you require different inlet and exhaust gaps!! is feeler is a must..
K Harris

This thread was discussed between 06/04/2009 and 07/04/2009

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.