To tickover, or not to tickover?

[James Ashby]

Dear all,

We took the 3 1/2 off for a rally today. All good fun, lots of interest from people, and all in all a very pleasant occasion.

Many visitors of course wanted to hear/see the engine running, and were fascinated by the mechanical advance/retard which as we all know allows for a very slow rpm at tickover, and even allows for the occasional lucky start merely by flicking the advance/retard with the ignition on - which I was happy to show a few people, much to the annoyance of the owners of a 1930s Sunbeam who were parked next to me.

In fact, they were so irritated, I was told in no uncertain terms that such low rpm activity would, and I quote: "Ruin the engine, as it has no splash on the top end, and we are all cringing every time you demo this".

Now, the engine is in fine fettle having been recently rebuilt, and I was thinking that with excellent oil pressure and flow the top end will not suffer, since one engine revolution at 200 rpm will pump exactly the same volume of oil to the rockers as one revolution at 500 rpm.

The only fly in the ointment that I can see is that oil splash into the bottom end of the bores from the sump may be reduced, but at very low engine rpm that shouldn't really matter?

Can anyone please advise? The engineer in me seeks a definitive answer, and I would clearly rather not inadvertently cause damage through having a bit of fun.

Many thanks

[Christopher Carnley]

James,
The cam in the distributor,and the engine controls should be in a central
"neutral" position,set when the engine first fires up.

The purpose of the hand controlled adv/ret,is for starting and running.The retard is useful in starting, and the advance for hills. It was never intended as a slow running adjustment.A retarded spark causes over heating. The valve gear and all essential bearings being pressure fed.

Buy a copy of the BDC Green Book.

[James Ashby]

Thank you very much Christopher,

I usually leave the adv/retard fully advanced when driving and running, and as you say, only retard a little when starting from cold - I am sure the owner's handbook suggested leaving it at fully advanced, but I will check whether it should be at the 'neutral' position normally, thank you for the prompt.

I know I don't often post on here (this is my first post) but I've known and worked on the car for the 40 odd years it has been in the family. However, it is only now that I am able to use the car more (the more the better!) and the forum is exactly why I joined the BDC - for queries such as this.

The 'trick' I was describing I only use occasionally for short periods to demonstrate the amazing smoothness of these engines even at very low revs, so I am not sure that overheating will occur too quickly . I don't use it as a slow running adjustment normally.

I was pretty certain that with all important parts pressure fed (and with Will Fiennes' excellent full flow oil filtration adaption) that there would be no issue, but the Sunbeam owners were quite aggressive in their assertion, and in spite of being told that all was pressure fed, retired with the comment "Well, it's your car, so feel free to ignore us completely" and thereafter refused to make eye contact for the rest of the day.

It sounded like hokum at the time - but their vehement assertions raised a sufficiently large question mark in my head that I needed to follow it through, so thank you again for your input and time.

And yes, I will re-read the manual!

[Dan Suskin]

I think it should also remember that the reason for starting on fully retarded dates back to the era before starter motors (i.e. pre-1913). Cars had to be fully retarded to prevent the engine running backwards when starting, as they were turning over at very low speed (hand speed) without any force to keep the engine going in the proper direction. Not to mention breaking the owner's wrist.

With a starter motor, even at low cranking speeds, the engine will keep turning in the proper direction until the engine is running and the starter disengages - with the ignition in a more neutral firing position, and even when advanced to a small degree.

There really is no need to be fully retarded to start anymore.

[Chris Card]

[quote="Dan Suskin"
With a starter motor, even at low cranking speeds, the engine will keep turning in the proper direction until the engine is running and the starter disengages - with the ignition in a more neutral firing position, and even when advanced to a small degree.
There really is no need to be fully retarded to start anymore.[/quote]

With my 4.5L, unless I fully retard for starting, the engine is inclined to baulk and kick back against the starter.

In my yoof I had a 12/60 Alvis which kicked back and bent the Bendix shaft because I forgot to retard it on one occasion. The Bentley starter has an outrigger that supports the end of the Bendix shaft.

Except when I have a memory lapse, I always fully retard the ignition for starting.

Chris

[Dan Suskin]

Chris

I do too. However, if the car kicks back against the starter when not fully retarded - in about a neutral position - it indicates that Neutral is not neutral. The position of the control arm is only as good an indicator as the person who set the timing. Lots of people set them slightly more advanced than suggested as they are driving with modern fuels, and often overdrives.

[John Murch]

James, if your engine will idle smoothly at very low rpm (how low?) I can't see why it would do damage.
With my WO long stroke 4.5 an idle below about 600 is distinctly lumpy and I could imagine it would not do things much good.
As an aside, my car has a vibration period at 2100 rpm, annoying as that is 70mph in od top, but altering the advance shifts the period, with no discernible change in power.
John

[Chris Card]

Dan,

Following current thinking, I've set max advance at 42.5 btdc rather than 45btdc. However, in practice, I find the optimum position on the lever is a bit less than fully advanced. However, I do have a higher diff (3.3, not 3.54), so that may be a factor. I also have an overdrive, which with the 3.3 diff, I find a bit overgeared, and the car runs best slightly retarded. 1600 rpm equates to about 60mph in overdrive.

Hi John,

I also have a vibration period between 1800 and 2000 rpm - I will try adjusting the asvance/retard as you suggest. My tickover at 450-500rpm is quite confortable - maybe it is down to differences intherevcounter drive ratios.

Chris

[James Ashby]

John,

As far as 'how low' goes, it's a bit hard to tell, but you can count the cylinders firing off, the rev counter is a bit wobbly at these speeds as I think the eddy currents are a bit weak, but suggests around 200 rpm. Much lower than that and it does have a tendency to die on you - oil pressure at these revs is still more than adequate at over 20 psi warm and I would expect the flow to be equally good.

If I could find my old timing light/strobe I could get a more accurate figure, but it doesn't seem worth it.

Like you, once it starts getting lumpy I advance things a smidge to prevent inertia driven shocks stressing things out unnecessarily.

As far as starting the beast from cold goes, I retard by about a quarter from fully advanced, and off she goes. Once started and the choke is off (normally only a few seconds after starting) I then leave the ignition alone until I judge the plugs to be warmed up, and then I leave the ignition fully advanced.

It is probably worth noting that the car is fitted with the higher ratio diff - and having got rid of the 'clonks' on the drive shafts/splines my late brother and I didn't want to introduce more noises from elsewhere that would compete with the windows rattling in their runners (I really do need to do something about that one day).

Do I notice the difference with the high ratio diff? No. The car behaves as perfectly as ever, and the occasional cruise up the motorway is a delight, although I am sure that some drivers are convinced that my car is not really 'old' and is a modern 'lookalike', since old cars were all very slow(!).

James

[Christopher Carnley]

Both the handbook and Green Book,recommend an idling speed of 500-600 rpm.
Axle ratio fro 10:41 to 11:41,so did you fit the ratio changing duplex gearbox the speedo drive?

"Clunks" are from worn wheel drivers/hub and halfshaft splines, and quite a racket.

[James Ashby]

[John Murch]

Chris, as you suggest the rev counter could easily be out a bit, in addition my engine retains its 3ltr phoenix crank which will doubtless cause variance with your engine. I may also have a higher c/r!
With regard to the 3.3 diff, I feel my engine could pull a slightly higher ratio (in o/d) but at present with 3.54 it Will happily hold 2500 up reasonable motorway hills in France (130kph) etc, much to the surprise of modern cars.
John

[Stephen Blakey]

Apropos not much; one of John Cockayne's party tricks at Coldwell Engineering was to run Ghost engines very slowly. 60 rpm was about the lower limit. You could mention that to the Sunbeam types if you see them again, to enrage them further.

[James Ashby]

Hmm, I may just do that.

Thanks for the apropos.

[Stephen Blakey]

Seriously though,

I have a psychotherapist friend who advises that, when faced with a narcissist you should, "stroke the ego and leave".

[Chris Card]

John - if you have a 3L crank in a 4.5L block, does that give you about 5.2L?
If so, you probably could run a 3.3 diff. My standard capacity 4.5L with 3.3 diff runs out of puff in overdrive on long, or steep hills. On undulating roads it is great and pulls up to and beyond the legal limit with no problem - this statement is, of course, entirely hypothetical!

Chris

[Christopher Carnley]

The owners of Rolls -Royce made cars, should always maintain a high degree of dignity, and not play party tricks for owners of lesser cars (all of them).
Louis must be rolling in his grave at that!

[John Murch]

Chris, 4680cc, so only a little extra.
To get 5.3lts you need a 110mm bore.

John

[Chris Card]

John - thanks for putting me right on that. Which camshaft to you have? When I got my car, it had a peaky Phoenix camshaft, which i replaced with a standard 4.5L one. The improvement in low down performance was fantastic. Does the longer stroke of the 3L crank make any significant difference that you are aware of?

Chris

[John Murch]

I've a standard 4.5 camshaft, it's difficult for me to say how different my engine is to a 140mm stroke one as I have nothing to compare it with. My c/r is well up as well. The output is much higher than on the very standard 4.5 that I used to own. My subjective view is that I have much more torque than standard.
John.