04-10-2018, 08:58 AM
(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.