Auto advance?

[ukmax]

Me again!

I've now sorted the oil leaks and had a good 30 mile run out today but was a little displeased with performance.

When I checked the timing, there seemed to be little or no advance as I revved, I know there is no vacuum advance but is there a centrifugal advance? an attempt to twist the rotor arm a little seemed to indicate that there is not.

I think I'm correct in saying that the 4 cylinder LeMans Special Speed is timed at TD, is this correct?

Finally, does anyone know what the points dwell reading should be?

Many thanks
David

[mikeyr]

take a look at page 29 of this PDF https://www.singercars.com/wp-content/u ... Manual.pdf The index in the book shows it as page 27 but the cover front and back take up 2 pages so if you type in 29 you will get to page 27.

It appears there is no advance on these cars, I assume the only advance is done at the steering wheel, sorry I didn't get any of that with my car, it had no dizzy or the stuff at the steering wheel so not sure, but that book should help, there are others at https://www.singercars.com/singer-manuals/ that may help also.

But the real answer will come very shortly from someone who knows...

[Peter McKercher]

The Le Mans ignition timing is 1 7/8 BTDC, but I wouldn't compare that to the 4AD. The first thing I would do is to make sure the valve timing is correct. Go to http://singerninehpengine.blogspot.com/ ... thing.html and find out how to do it. This is most likely your issue.

[jeans_old_man]

Peter is right. The valve timing is more critical than the ignition. The diagram in the manual is a little confusing as it shows the ignition in advance of the valves but the table at the bottom of the page states IGN = 1" BTDC and inlet opens 1 7/8" BTDC.

The bob weights in the DK4 distributor provide automatic ignition advance. There is a good description here: http://www.da7c.co.uk/technical_torque_ ... nce_di.htm

From memory the maximum advance is 18 degrees and this is stamped on the base plate. The 18 degrees represents 36 degrees at the crankshaft and this can be checked by marking the fan pulley and observing with a strobe light as the engine is rev'd. Full advance should be obtained at 3000 RPM.

When I tried this I noticed erratic timing during idling. The cause turned out to be a strong spring on the points 'fighting' the advance weights. I fitted electronic ignition which cured the problem and gave much smoother idling.

[ukmax]

Thank you for the responses,

I think there is some confusion with regard to my car which is a 1935 972cc Singer LeMans Special Speed and appears to be timed differently to the standard 9HP sports. According to the manual kindly forwarded by Mike, the ignition fires at half an inch BTDC and not at TDC which I had read elsewhere as being correct.

When I checked the ignition timing, it was firing at TDC (assuming that the / in the 1/4 mark is TDC!), therefore it is actually a bit retarded from where it seems it should be, the only problem I noticed was that there was no auto-advance when I revved the engine.

I'm not actually certain exactly what distributor I have fitted to my car but I will delve inside and see if there is a centrifugal system, because if there is, it must have broken or seized.

The car has been running fine for several years and as I haven't touched the valve timing, I must assume that all must be well in that department.

David

[ColinB]

Probably worth sending the distributor to the Distributor Doctor. They are very good and will restore it to its original condition.

[jeans_old_man]

The 1935 Special Speed was fitted with a magneto and high-lift camshaft that required 'flat' rockers on the inlet valves. This accounts for the different ignition and valve timing to the Sports model. It is interesting to note that the increase in performance that this gave only cuts in above 3000 RPM.

After discussing this with other members it seems that many owners replaced the magneto, which was popular with boy racers in the '30s with a DK4 distributor. Apparently the drive gears were not up to driving the high inertia of the magneto.

[ukmax]

The PO had the distributor rebuilt not long before I purchased the car and I have done hardly any miles. Furthermore, the car stood unused for over 2 years so lack of use could have caused the bob weights to sieze up (if this is what's happened).

Thank you Brian for the most interesting information, I had completely missed the reference to a magneto when I read that section, my eyes were drawn to the timing list below.