Ignition timing

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David2021
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Ignition timing

Post by David2021 » Sun May 28, 2023 10:09 am

I don't want to monopolise the thread, but...
I fitted a brand new correctly numbered DY4A (no vacuum advance) distributor last year (anyone need a Wolseley Eight distributor?. Only one numeral different to a Rover 12....? :lol: ) and set it up according to the book settings.
Two questions
1. It feels "loose" despite the clamp and the locating bolt both being tight. The whole unit, not just the rotor arm against the springs. How can that be?
2. As we now use 95-99 octane fuel , where should the " Octane selector" be set? As the original settings must have been for "Pool" petrol which had an abysmal octane rating ..under 70 at worst I believe, so it would suggest it must be off the scale on modern petrol.
Or is there advice on revised "set up" data to have an advanced setting to have the selector on its mid point?

HAD501
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Re: Ignition timing

Post by HAD501 » Sun May 28, 2023 8:37 pm

David, some thoughts on your questions:-

1 - I think the set-up is bound to be a bit sloppy - mine has possibly 5 degrees of movement, but it seems to work OK.

2 - I've had a look at the Instruction Manual for 1947 models (first time in ages) and it recommends setting the timing with the octane selector at "0" for "first-grade" fuel (page 62). I think the idea was that the timing could then be retarded for lower grade fuel. At the moment this is what I have done with my own car. More interesting, perhaps, on page 7 of the manual, Rover's recommended fuel was "a good Alcohol Blend" or "Ethyl Petrol". I'm currently using E10 and it seems to work OK. Have we been worrying too much about modern fuel?

On the Platinum rally, I've booked the Morgan tour and the meet at Shelsley Walsh - I hope our paths will cross!

DaveM

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luli
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Re: Ignition timing

Post by luli » Mon May 29, 2023 7:23 am

I replaced the DKY4A with a digitally advanced 123 distributor, in which you can tune the ignition advance curve to perfection. The engine feels much happier.

https://lulis.org/2023/02/26/%d7%a7%d7% ... %a8%d7%a8/

and

https://lulis.org/2023/01/08/%d7%94%d7% ... %99%d7%aa/

and

https://lulis.org/2022/03/09/%d7%a7%d7% ... d7%99-123/
Rover 10 1946 RHD
Rover 10 1947 LHD
Rover 12 1947 tourer LHD
http://lulisml.wordpress.com/

David2021
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Joined: Sun Jan 31, 2021 4:29 pm
Location: Stratford upon Avon

Re: Ignition timing

Post by David2021 » Tue May 30, 2023 11:25 am

Thanks Luli...very impressive that 123 system. Did you measure performance "before and after"? or subjectively does it feel better.
At the moment, having fitted a NOS distributor of the correct type I just want to know where to set it to suit E5 99 octane fuel!
I will also check the clamp again to make sure it is working properly, I suspect that it is the culprit for the slightly wobbly fitting.

David2021
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Re: Ignition timing

Post by David2021 » Tue May 30, 2023 5:37 pm

Clamps all good. The looseness appears to be in the drive...drive slot perhaps. As the distributor is new. I'll put up with it!

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luli
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Re: Ignition timing

Post by luli » Tue May 30, 2023 9:45 pm

Ignore the micrometer etc. Use a vacuum gauge, loosen the clamp and rotate the upper side until you get the best vacuum. tight the clamp again.
With the the 123 the engine is smother, pules better and consumes less petrol.
Rover 10 1946 RHD
Rover 10 1947 LHD
Rover 12 1947 tourer LHD
http://lulisml.wordpress.com/

David2021
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Re: Ignition timing

Post by David2021 » Wed May 31, 2023 5:17 pm

There is no vacuum control on the distributor, so if I get hold of a vacuum gauge what do I do with it....? fit it to the manifold lubricator take off ??? Apologies for ignorance!
D

SHyslop
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Re: Ignition timing

Post by SHyslop » Thu Jun 01, 2023 9:20 am

Dear David, you have answered your own question with the correct answer. Looking purely at the ignition side of things, as the engine fires with greater or lesser power depending on the distributor position, the suction created on the suction stroke of the pistons creates a higher or lower vacuum which will be recorded on the gauge. Fortunately, the lubrication pump take-off provides a convenient point to attach a Gunson's Lo Gauge or similar. The answer on other vehicles used to be to drill and tap a hole in an alloy manifold using plenty of grease to catch the swarf and not have it go into the cylinders. If you'd had a Ford there would have been a similar connection powering the wiper and Saab used the same idea on the original 900s to operate the ventilation controls.

Once the gauge is connected, rotate the distributor slightly and note the readings. There should be an optimum point of highest power (greatest suction) and smoothest running. The tickover on these engines shouldn't be as slow as on some older vehicles as you don't want the engine to stop when freewheeling - I think your car might be too new to have the Startix system on it - but if you do end up finding the point of good running is also rather advanced from where you started, the throttle stop will need adjusting back a bit to slow it back to normal.

Just in the passing, and with complete and full respect to the people who have found the opposite, about 20 years ago I had a Volvo 123GT which was near perfection except that it just lacked the go I was expecting. Having been over everything, I bought a 123 distributor (the numbers were just coincidental, by the way). It made no difference, it was a lot of money for no benefit. I would accept that if there is a distributor fault or you have a seriously incompatible distributor, it is a fancy bit of kit to solve the problem but there are still a lot of cars running very nicely on comparatively crude, and cheap, setups. As with electronic ignition, just because something is electronic doesn't make it a magic bullet.

I have a 1947 12 and its distributor is also somewhat loose compared with the others. It has worked ok for the 10 years or so I've had the car but it is not the completely firm arrangement I usually associate with these cars.

I never found an answer with the Volvo, by the way, maybe my expectations were too high.

In thinking some more about this, here is something to consider. Before about 1934/35, the distributor was a fairly simple device with no weights and no vacuum connection. It had the appropriate number of lobes for the cylinders and basically that was it. To start the car, you retarded the manual control "a bit", once going you set the ignition to "normal" and when you came to a hill you advanced it "a bit". I ran Austin 7s and 12s for years with these and they worked well. If you disregard the advance mechanisms, you should be able (with a few caveats we'll leave out to save space) to fit any suitable four cylinder distributor to your Rover and it should start well, idle well and maybe with a bit of manual advance it should run generally well on the near level i.e. pull through the gears, run up to 35/40 or so. If your car were to do that, it then becomes a question of : will it accelerate better or pull better with some technology (albeit 100 years old) applied? In other words, there should be a starting point at which your new distributor works well to start and move the car and then it becomes a question of improvements to the performance in detail i.e. centrifugal advance curve controlled by the weights and weight springs.

The one gadget I have found to be useful is a Gunsons Professional gastester. An engine that is receiving too much fuel won't run well because there is a ratio (stoichometric? without looking things up) of about 15 parts to air to 1 part of petrol. More than that, the engine starts to choke itself and too weak, not enough power. The Gunsons meter does basically what your MOT station does except with a cheaper machine and shows the value of the CO2 emitted as a digital readout. Under 4.5% for a 70s car would pass an MOT and I believe is getting close to the 15:1 ratio, up to about 7% is usually the top end of what I'd be looking for on an older car but I just mention this as they made a cheaper unit in a yellow case which had a moving coil meter but it had the Morris 10 speedometer needle problem, the needle could show a wide variety of readings all at the same time whereas the green cased Gunsons device has a digital display that is pretty accurate. If you knew someone who had one it would be worth borrowing for an hour to check that the mixture is right, or maybe you have a friendly MOT station who would hook it up to their machine and just make sure. If the mixture is wrong, it can make setting the ignition timing unnecessarily difficult, particularly if the Rover has a Solex carburettor with the wrong or worn or damaged jets.

David2021
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Location: Stratford upon Avon

Re: Ignition timing

Post by David2021 » Thu Jun 01, 2023 4:44 pm

Thanks for the helpful answer. The distributor I have is the correct one, and new old stock,so there is no wear at all.
I am sure I can get hold of a vacuum gauge, so that will be my route. I have not used one before, so a new experience.
I too am familiar with manual advance/retard on Austin Sevens☺ ".Don't advance it too much or it will kill the bearings. Find the sweet spot"
The Solex carburettor is in good condition...decent spindles, correct jets etc, so let's see what the vacuum reads!
David

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