The advice from a Ford Master Techician is that the tappets on my KA engine should not be adjusted when cold. I have always adjusted the tappets when cold as stated in my manual. At his chain of dealerships it is common practice to run the engines through an engine flushing procedure using Forte engine flush, then adjust the tappets. I thought that the sole reason for adjusting the tappets was to allow for the expansion when hot so I can not understand the logic behind this practice. Had this advice come from anyone else I would have totally discounted it. I hope someone out there can either agree with me or explain why I am wrong.
Old A series engines. 12 thou cold, 11 thou hot. Always do them hot as it's the normal condition.
Adjusting while idling? Yes, old vauxhalls and Opels. Many years ago a neighbour used to wake me and my next door neighbour up early every morning with a rattly Opel. One weekend we suggested we could do the tappets for him. A real palaver, but undisturbed sleep from then on! He couldn't believe how quiet the car was. God knows what his garage did during services!
It depends on the manual! I believe advice has changed over the years. The original instruction book for my '58 Minor says 12 thou cold, but that is aimed at owners, not garages. However, the official BMC workshop manual I have (I believe this is from late '60's as it covers the 1098 Minor) says adjust to 11 thou hot, allowing the extra thou for a cold engine.
If it's just a check, you can check the valve clearance quite quickly, so they don't cool off much.
The pushrod engine in the Ka dates back to the days when tappets were adjusted hot or cold. Aluminium heads were usually adjusted Hot - iron heads cold. Sometimes it was the other way round. Going back even further, Vauxhall tappets used to be adjusted hot, with the engine running.
It was a fiddly job with the adjuster jarring the screwdriver and spanner and oil being flicked all over the place. 6cyl engines were a bit easier as they idled slower and the rocker didn't move so often. The trick was to get the feeler blade sliding through the gap with just the right amount of drag. Too tight and the engine misfired with the valve being held open, too loose and the tappet and blade would 'clack' Adjusting in this way also allowed a noisy tappet to be located first time,you just slid the blade through each gap until the noise stopped. Ordinary feeler gauges didn't last long as they flattened and took on a permanent curve. Vauxhall supplied long feeler 'strips' and as the used end became damaged it was cut off.
That stirs the memory! I remember we developed a technique for adjusting tappets on Viva\'s and Chevettes using feeler gauge and vacuum gauge. Result was a very quiet engine that would go like a ferret up a drainpipe and idle as smooth as silk!
In the past we set all Ford push-rod clearances whilst running-long strips of feeler steel were available;incidentally,my dealer tries to get me to have Forte oil/fuel treatment at a considerable extra cost but he has now given up claiming that it is Ford recommended-it isn't.The first time he added it to my bill I refused to pay-I did not ask for it and it is not part of the Ford service schedule.
Quite right about Vauxhall engines. We used to do them running. The Cavalier/Manta 1600 & 1900 CIH engine, tappetts were set to 12 thou, and I used to cover the timing chain with a piece of card to prevent oil splashing everywhere. The 2000 engine had hydraulic tappetts, so no adjustment was necessary.
Chevette's and Viva's were set to 8 thou on the 1256cc OHV engine, and 6 thou inlets, and 10 thou exhausts on the Opel Kadett 1196cc OHV engine.
Adjustment on all these was by a single nut in the centre of the rocker.
Remember those special tools advertised in Practical Motorist, like a kind of torque wrench that measured how far the screw moved in? They compensated for worn rocker ends which a feeler gauge would simply bridge.
Or you make up your own gauge, by counting turns and calibrating with a feeler, composing a rule like
"1 turn = 5 thou", or something.
I remember those, marketed by SPQ or PQR or something like that. Totally useless.
Many of you chaps will remember the the adjustment on the GM 'slanted' OHC engine from the 60's. A tiny allen screw located inside the cam follower, one tappet always 'clacked' and ten minutes after adjustment 'clacked again. I think that these engines were the first on the UK market to be fitted with cam belts. The trade advertising at the time went somehing like "As long as at least eight teeth are in contact with a pulley, these belts are stronger than steel"
I'm sure you're right about GM being the first in the UK with a belt-driven camshaft - on the slant-four Victor in 1968.
I mistily recall that the very first belt-driven camshaft was on GM's Oldsmobile. When these were sold into Canada, snow got trapped between the belt and sprockets and forced the belt off! Snow-excluding covers were quickly introduced as a cure.
I'm sure John is right. The Viva HC was fitted with a cambelt engine later on, 1971 or 1972, with a choice of either 1800 or 2300 cc slant-four engines. Fairly pokey for the day but with mediocre handling.
The slant-fours were good engines except for two relatively minor problems:
1. The oil pump was high up in the cylinder block and would drain off overnight after a hot run (i.e. thin oil). Priming it next morning could take quite a while if the oil pump was at all worn -- fairly harmless but caused an annoying rattle from the big ends etc.
2. The 1800 version occasionally suffered misfiring from cold, caused by petrol wetting No. 4(?) spark plug, cured by fitting a slightly smaller jet in the carburettor.
Yes, I've still got mine. I used it for many years on BL A Series and Avenger/Sunbeam motors. I found it to be an excellent tool. It now languishes in the bottom of my tool box, unused for at least 13yrs since I purchased my first car with hydraulic tappets.
Tappets can be adjusted hot or cold as long as you have the appropriate settings.
Garages find it more convenient to set them hot as a car has to stand for quite some time before you have a truly cold engine.
To find hot settings - set cold as stated in manual - run engine until hot then measure tappet free-play.
Sorry, I find it hard to accept that all engines can have the valve clearances set hot or cold. If the engine designers could allow this, they would give alternative hot/cold figures.
'Cold' can vary but I would guess it would almost always be in the range 10-30 Celsius. What is 'hot'? That depends on how long and hard the engine was run before switch-off, the ambient temperature, and the time taken to get to and remove the top cover etc. 'Hot' could be anywhere from, say, 40-100 Celsius. Maybe these guesstimates are a bit out, but you get my drift.
Best to play safe and stick to the published method, even if it means leaving the car to stand overnight. Much less of a problem than burnt valves and seats!
The Haynes Manual for my Proton/Mitsubishi engines advises that the tappets are set hot. Or if set cold then checked at running temperature and if wrong presumably re-set hot. So you might as well do it hot to start with. The cold/hot settings are in. 0.07/0.15mmm. and ex. 0.17/0.25mm. A considerable difference, so allowing for variations in expansion between different heads due to tolerence allowances might it not be better to do them hot just in case? Being a coward I did mine cold, one is noisy and I am nagged by doubts.
I don't think we are saying that the valve clearances on *all* engines should be set cold.
Setting "hot" or "cold" doesn't just depend on cyl head expansion but takes into account many other engine design variables that may not be obvious to the owner or technician.
If the Haynes manual says that yours should be set hot, then I expect that's correct (even though Haynes don't *always* get things right). However, when manuals say "set cold" (or "set hot") then that should be the case, no argument.
I should have made it clear that I was refering to variations between engines of the same model rather than engines in general. I think all the information you could ask for is in yours and the rest of the comments in this thread and probably boils down to 'if it's an ali. head best do it hot' unless told otherwise. I think if you do it cold and the (hot)settings are correct when the engine has warmed up that's possibly a bonus.
I agree with a previous remark about the engine cooling down while you adjust, by the time I've stopped fiddling about not only is the engine cold but winter has set in. Perhaps Carl2 could let us know what finally happened?
Almost always the initial setting will be done "cold" when the engine comes down the production line in the factory, therefore the design engineers will have calculated the setting for a cold engine. This may be one reason why we are typically told to set them "cold" when servicing -- the figures have already been very precisely calculated.
I'm still not sure about 'if it's an ali. head best do it hot unless told otherwise'. Even with an aluminium head, I would guess that the original design calculations aimed towards "cold" production-line setting, though of course the extent of subsequent thermal expansion will have been taken into account in all calculations!
Out of curiosity I looked in a couple of other Haynes' Manuals I have. Vauxhall Astra 1980 to 83 and VW Golf/Jetta '84 to 92 both of which suggest setting clearances at running temperature. An Autodata manual for Volvo 340/360 seems to suggest you set them cold but gives data for both hot and cold.
Going back to the days of the Daf air cooled aluminium headed engines. The tappets had to be set hot. The clearances were 4thou inlet, 6 thou exhaust. Adjusting a cold engine led to tappet clank when hot. Adjusting a hot engine a bit too tight meant that the engine wouldn't start when cold. Correctly adjusted, when cold, it was just possible to turn a pushrod - with no lift.