I'm aware that the A7 crankcase is marked with a + or - figure for the mesh of the timing gears. The case I am fettling is +1 and a 1/2. Question: Do both the camshaft AND crankshaft gears have to be marked as + 1 and a 1/2 or just the crankshaft gear?

Location: Moist and warm Hertfordshire

I believe both.
Regards, Stuart

Hi Nick, Speak with VINCE LEEK, I know that he will be able to help.......

Location: Near junc 8 M25

Good evening. When John Platts set up his business I understand that he had gauges made to measure the 'toe in or toe out' of the camshaft vis a vis the crankshaft. This is what the + or - refers to, apparently Austin could not machine the cam and crank perfectly parallel. However John Platts' experience was that the numbers were erroneous, over the passage of time the crankcases having 'moved'.
I have always been of the opinion that only the cam shaft gear was 'adjusted' the crank being 'standard' and when I have rebuilt engines I have taken gears from the stock I have amassed and fitted them by 'trial and error' until I have a pair that run well together with no slack or tight spots and minimal backlash and rarely do the numbers coincide with those stamped onto the crankcase.
I'm sure that others can throw light on the subject.
Regards from the creative county
Stuart

Location: Staffordshire

hi stuart,

as the gears are usually worn as well.

I have the same method as yourself.

"trial and error"

and a big box of old timing gears.

tony

Thanks to all for the replies. I have followed the trial and error method with different gears and found a decent fit. In the process of fitting the camshaft gear I could not get the float down to 0.002" but then realised there was this sitting between the back of the gear and front of the cam bush. I can't see any reference to it in Woodrow so am I to presume it is a shim fitted by a previous fettler? I have got the float to 0.003" without this 'shim' so is it OK to leave it out?

Location: Moist and warm Hertfordshire

Not sure what it is but I would be sure it is not a standard part and should be left out

Tony.

Location: Malvern, Melbourne, Australia.

So is it alright to mix and match crankshaft and camshaft timing gears from different pairs?

Thanks

John

No-one has mentioned the dynamo gear!
Dave.

Location: Sheffield

On the whole the gears have seen so much use over the years that the original markings are pretty academic.
If they are meshed too loosely the engine will be noisy. If too tight the gear can fail in use.
I have several crankshaft gears and just try each in turn against the camshaft. No block fitted so that gear backlash can be felt.
There should be just a tiny bit of backlash between the gears and they should turn silently. If the are meshed too tightly they'll make a rumbling noise. If too loose there'll be backlash.
The clearance stamp on the gear should help selecting the right one.
The gears are often chipped around the keyway. I don't think that matters particularly.

How does the Austin marking of tolerance on the timing gears apply to replacement gears in period such as Remax, or for that matter brand new gears made now. As far as I am aware neither Remax or modern manufacturers made/make their gears with different tolerances.

Thanks, Jim. I've only got two other sers (on old engines), so hope I'm lucky.

John

Since all three gears (dynamo gear included) mesh together surely any newly manufactured timing gears should be a three part set. Ideally you wouldn't want to mate any old crown wheel with any old pinion on the rear axle. I know ithis has been done before.
Dave.

Location: Sheffield

The shim you found is a danger: eventually it will break up, and you don't want the bits getting into your nicely meshed timing gears. Shims should only be used between components which do not move in relationship to each other. If you want to reduce end float you can lap the timing gear onto the shaft with fine grinding paste, but I would accept your 3 thou without any worry.

Robert Leigh

Location: Cottenham, north of Cambridge

The 'shim' in the picture looks like rubber rather than metal. Perhaps it was an attempt to reduce the oil flow from the cam bearing.
The front bush is very liberally lubricated and overflow from it lubricates the gears.
Often the feed hole is reduced in diameter to stem the flow a bit and increase pressure at the big end jets. However they don't need much and there's so much oil flying around inside an A7 engine I don't believe lubrication is a problem.