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MG MGB Technical - Tappets and springs

I am just getting round to my noisy tappet now the car is off the road. Number 3 rocker is very noisy; I have adjusted them all the same and if I put a feeler gauge under the rocker the noise stops. I have just removed the rocker shaft and the surfaces show a little wear but not too bad. There is a flattening on the bottom of the push rods but they are all the same. Any ideas what the problem might be?

I also noticed the car is sagging to the left about an inch. I take it this is a weak leaf spring. Are new springs good quality?
Rod Merrall

You have described a situation many of us have experienced. Probably the rattle stems from the interface between the camshaft and a cam-follower; one or both are worn and although you are able to set up the tappet accurately - uneven wear will open the tappet gap and lead to the rattle. Flattened pushrods and loose rocker bearings don't help.

on your second question,good quality springs are available from the usual sources - you might be well- advised to check the bushes and the anchor points front and back while making a plan to change things.

Roger Walker

There is quite a large arc where the rocker should be fully up and not move, in theory the back half of the cam lobe at least. But on mine and others that isn't always the case and the clearance can be changing round the back of the cam, for whatever reason. That leads to difficulty getting a repeatable measurement of gap if it is changing at the point you measure it, as well as noise.

I looked for the largest gap when the rocker should be fully up, and on several valves that's not at the usual 'rule of nine' measurement point. Found where it is the biggest and adjusted them there, and it did make a difference. Ideally you need a dial gauge for this.

Sagging at one corner can be caused by a problem at the diagonally opposite corner, you need to take measurements at all four from the centre of the hub to the bottom of the trim strip, with the car standing on flat and level ground. There can be other reasons for unevenness as well as the springs themselves.

There have been problems with spring quality for years - probably a decade or more now. For some time leaf springs were far too hard and/or arched which made the rear sit right up and the rebound strap was taut even with a fully equipped car, once you could get it attached with additional weight in the boot. Likewise front springs have not been to the spec free height, and not even to the same free height for a given spec. I've not heard of things getting any better (which isn't to say ...), only that they are in short supply.
paulh4

Try GB Springs. UK steel UK made to correct spec But don’t expect them at the same price as the usual suspects!
Michael Beswick

Some time ago I found a statement on the Cheshire MGOC website https://www.mginfo.co.uk/westcheshiremgoc/home?page=10 saying 'BMH guarantees' the quality of GB Springs leaf springs, but have not been able to find a statement to that effect on either site. Although they reference the OE part numbers GB Springs use their own part numbers, which usually means they are not OE.
paulh4

I agree with PaulH that the B series camshafts suffer from too much base circle run out. They were ground on centres in north works Longbridge. Who knows how 'tired' the machines were that did it. (I wonder what the Indians do ?) K series for example were made on brand new machines and centerless ground. (they had to be spot on because of the hydraulic tappets).
I've always struggled to get my tappets quiet. I've already renewed everything in my valve train. See if you can isolate which valve is causing the tapping. Hopefully if its an inlet you can try tightening the clearance to 13 thou. Its riskier with exhaust as they get very hot. I just do the troublesome ones tight on the 15 thou feeler. They are still pretty noisy until the engine is well up to temperature. I think its just a characteristic of the engine at the end of the day. If only we could get our hands on the cam profile drawing. The number would be a start.
I've always find that road springs settle. I'm running rubber bumper front springs now to improve ground clearance (but with no spacers in the cross member) They have settled to pretty much the ideal ride height. The car is level unladen but its probably down at the rear with occupants and a full tank. Oh (I have a 3/4" anti roll bar.
Paul Hollingworth

With my camshafts produced by Clive Cams (Melbourne Australia) I don’t see the base circle run out mentioned by our UK brothers. I don’t use the Rule of 9 but rather the “rocking method”. When no 1 cylinder inlet and exhaust rockers are rocking, adjust no 4 cylinder valves (both), when no 2 cylinder is rocking do no 3 , when no 3 is rocking do no 2, when no 4 is rocking do no 1. (Rocking mean exhaust valve is just closing, inlet valve is just opening). Benefit is half the amount of engine turning.
Mike
Mike Ellsmore

Agreed Mike ,any decent cam (like Clive's)should have a consistent base circle
I'm lazier still
I just go to tdc No1 and adjust the 4 loose rockers, then round one turn to tdc No1 again and do the other 4
Nice and quick if you're doing them to a hot running spec

willy

William Revit

It took me ages to find out what 'on the rock' or 'rocking' meant. With a consistent base circle you should be able to adjust a valve anywhere round the back half of a lobe and more. But you can do two at a time using the 'Rule of Five' which probably no one else has heard of. There is a short period when both valves of a cylinder are partly open, and you can then adjust both valves on its five's complement cylinder as that should be close to TDC on it's compression/expansion strokes. I.e. when cylinder 2 is like that you can do cylinder 3, 1 with 4 like it and so on.
paulh4

Paul, I'm still not sure you understand what rocking is.
"There is a short period when both valves of a cylinder are partly open"
What you are describing is exactly what Mike said, the rocking method

I still think the one full turn method is the quickest/easiest -
Rocking on no1 tdc and do all the loose rockers, valves 8764
------then round one full turn to tdc again and do 1235
It works on 6 cylinder engines as well but not on 8cyl-too many lobes overlapping

willy

The nine method doesn't work on all 4cyl engines but the five method does
William Revit

Paul, I'm still not sure you understand what rocking is.
"There is a short period when both valves of a cylinder are partly open"
What you are describing is exactly what Mike said, the rocking method

I still think the one full turn method is the quickest/easiest -
Rocking on no1 tdc and do all the loose rockers, valves 8764 then round one full turn to tdc again and do 1235
It works on 6 cylinder engines as well but not on 8cyl-too many lobes overlapping

willy

The nine method doesn't work on all 4cyl engines but the five method does
William Revit

I'm not sure what you mean in your last sentence - MGB engines? Or non MGB engines? With the cam that I and others have none of the methods work properly. If the gap is changing at the point you alter it it's very difficult without a degrees wheel on the crank to get consistent measurements, which is why I do it at the point of largest gap. I spent time working out where that was for each valve, then noted where other valves were, and that way I CAN get consistent measurements. And since then I haven't had to alter them one year to the next anyway.
paulh4

Sorry Paul, yeah that last sentence didn't refer to MGB engines in particular, it was more a general statement covering all 4 cylinder engines
An example would be Ford Pinto 2.0 engines where the valve arrangement goes IEIEIEIE as against MGB at EIIEEIIE - The 9 method won't work on a Pinto but 5 does
Cheers
willy
William Revit

This thread was discussed between 06/12/2021 and 21/12/2021

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