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auto vs. manual ignition setting? - JonE - 03-10-2018
"There are two types of distributor: manual advance (on the steering wheel) or automatic advance.
Ignition timing: manual distributor: points open at 11⁄2“ BTDC measured on the top of the flywheel.Automatic distributor: points open at TDC on flywheel." is on the Dorset Club Technical Sheet which is generally quite useful.
I'm just trying to get my head round this for the manual setting. Does this mean that the manual setting is set when the setting lever is fully extended to ADV?
I'm presuming the lever has a set amount of movement to Adv and R, or is there ability to tweak/optimise this? And the lower advance (than later cars) explains the difference between 1 1/2" BTDC and 1 7/8" which is quoted elsewhere for the later ones?
RE: auto vs. manual ignition setting? - Bob Culver - 03-10-2018
This topic has been laboured on many occasions. The Manual are set at full advance. If the car is not to be driven by strangers extra advance can be allowed and used primarily for experiment. For ordinary cars driven sedately many consider about 1 1/2 advance adequate.
The Manual advice wrongly repeated for the Auto in 1st Ruby handbook and repeated in many other books has caused endless confusion and needless engine stresses over the decades.
Actual characteristics of present day auto distributors is anyones guess.
My 13.11.17 post under 65 Timing covers the topic. Other posts refer more to advances for the rpm and ultimate power enthusiaits with new cranks.
Advance is very stressful of crank.
One inch on flywheel is 11 deg.
Noise is not necessarily an indicator of power.
RE: auto vs. manual ignition setting? - Hedd_Jones - 03-10-2018
Follow the instructions in the manual. Except aim the 1/4 mark on the flywheel with the oil pressure gauge pipe. Set lever in full advance. Set dizzy so the points are just opening at that point (for no1 plug lead).
Turn it wound till it comes round next time and check. Often the slack in everythi g means it may not be quite right.
Itll start easily when retarded, and the sweet spot will be in the range of the lever.
With auto dizzy theoretically you set at tdc. Points just opening.
RE: auto vs. manual ignition setting? - JonE - 03-10-2018
thanks both. The search is a pig so no bad thing to reinvigorate..
here is the thread that Bob refers to http://www.austinsevenfriends.co.uk/forum/archive/index.php?thread-451.html
Hedd - I infer that the 1|4 mark being 'put' to the oil feed pipe is easy-speak for it being approx 1 1/2 inches away from the top of the flywheel... havent got a car to hand but will measure!
RE: auto vs. manual ignition setting? - Hedd_Jones - 03-10-2018
No idea how far from TDC it is. Never measured it.
RE: auto vs. manual ignition setting? - Chris KC - 04-10-2018
(03-10-2018, 09:08 PM)JonE Wrote: "There are two types of distributor: manual advance (on the steering wheel) or automatic advance.
Ignition timing: manual distributor: points open at 11⁄2“ BTDC measured on the top of the flywheel.Automatic distributor: points open at TDC on flywheel." is on the Dorset Club Technical Sheet which is generally quite useful.
I'm just trying to get my head round this for the manual setting. Does this mean that the manual setting is set when the setting lever is fully extended to ADV?
I'm presuming the lever has a set amount of movement to Adv and R, or is there ability to tweak/optimise this? And the lower advance (than later cars) explains the difference between 1 1/2" BTDC and 1 7/8" which is quoted elsewhere for the later ones?
Yes set a manual distributor at full advance as this is the 'critical' value. There is considerable range (more than an auto advance unit) and fully retarded position is just for starting.
How much is another question. The racing chaps will take it up to 27 degrees or more fully advanced; but they drive everywhere at 6000 rpm. This may be inadvisable on a run-of-the-mill engine. I suggest 20 or 22 degrees max advance (n.b. at the flywheel) is a reasonably 'safe' value. It's also somewhat more than you'll get with an auto-advance unit set at TDC.
In reality each engine has its own needs depending on a combo of factors (compression ratio, carburation, etc). Use the recommended values for initial set-up but then listen to the engine. If it's lifeless it may need a tad more advance, if it's harsh and rattley back it off a bit. Far better to run retarded than over advanced.
RE: auto vs. manual ignition setting? - Colin Wilks - 04-10-2018
A very useful ready reckoner a forum member told me about is one tooth = 4.5°.
I had calculated that the A/R range would be around 24°, but checking it by using a lamp on the points and looking at the flywheel shows I have a range of about 18°.
I have concluded that trial and error is the best bet and now have the static timing set with the timing mark opposite the oil gauge take off (about 18°BTDC), with the A/R lever at its mid point (I'm the only driver).
Make sure that advancing the lever turns the distributor anti-clockwise. It's easy to get the linkage arse about face.
RE: auto vs. manual ignition setting? - JonE - 04-10-2018
Colin - so that thus gives you manual range from 27 degrees BTDC to 9 degrees BTDC overall? (i.e. You are setting "that" point at lever mid point rather than on full advance which seems to be what Hedd is advocating?)
RE: auto vs. manual ignition setting? - Colin Wilks - 04-10-2018
(04-10-2018, 09:44 AM)JonE Wrote: Colin - so that thus gives you manual range from 27 degrees BTDC to 9 degrees BTDC overall? (i.e. You are setting "that" point at lever mid point rather than on full advance which seems to be what Hedd is advocating?)
Hi Jon
That's right. I set it up like this so I could experiment whilst driving, although setting the static timing with the lever fully advanced does of course prevent anybody over advancing the timing inadvertently. I don't think it really matters provided you are the only driver and you know what you've done. It seems logical to me that if you have a control lever it should bracket the normal range, i.e. never be used at fully on or fully off.
RE: auto vs. manual ignition setting? - David.H - 04-10-2018
(04-10-2018, 09:04 AM)Colin Wilks Wrote: A very useful ready reckoner a forum member told me about is one tooth = 4.5°.Anti clockwise viewed from above?.....
I had calculated that the A/R range would be around 24°, but checking it by using a lamp on the points and looking at the flywheel shows I have a range of about 18°.
I have concluded that trial and error is the best bet and now have the static timing set with the timing mark opposite the oil gauge take off (about 18°BTDC), with the A/R lever at its mid point (I'm the only driver).
Make sure that advancing the lever turns the distributor anti-clockwise. It's easy to get the linkage arse about face.
David