Checking distributor maximum advance

[steg1970]

I want to check that my distributor is giving me maximum advance at high revs. I'm looking for 30-32 Degrees from the early black cap distributor on my 1300. My snap on timing light has the advance and retard feature but I'm not sure where I'm starting from. If I remember correctly the standard advance at idle is 10 degrees so it stands to reason that the pulley notch is positioned at 10 degrees, therefore with my timing light set at zero when timed to this mark I'm then looking for 20-22 degrees at full revs.

Is my thinking right or have I completely miss understood what I'm trying to achieve?

[jimbob-mcgrew]

that marker on the crankshaft pulley is 10 degrees BEFORE top dead centre (BTDC), and when in position, in-line with the pin, the marker on the other upper camshaft pulley should also be in-line with its pin/slot.

thats the mechanical timing side of it, the motion of the engine, thats run by the belt and is always the same.

sorry if you know all this already.

on my 1300, zero degrees is about a centimetre anti-clockwise of the 10 degree pulley notch (when looking at it from the drivers side wing).
the ignition side your going for, (the spark), ideally with modern day fuels, you want to set it up about 6 or 7 degrees before top dead centre. instead of the 10. which is about 3 or 4 mm to the left of the marker.

test the vacuum unit on the dizzy by sucking on the hose going to it, if you feel resistance, it means its probably functioning alright, if it feels like your breathing thru a straw, the units dead.

my unit is currently dead at the moment, and ive had to set my timing up at zero degrees to compensate for it, the car drives like crap otherwise.

check the timing with the gun, whilst the vacuum hose is both plugged in, and unplugged, you should be able to see a difference in behaviour of the markings while its revving from either test. judging by the movement of the markers, you can take a guess on degree amount - 1cm is roughly 10 degrees.

[meritlover]

I want to check that my distributor is giving me maximum advance at high revs. I'm looking for 30-32 Degrees from the early black cap distributor on my 1300. My snap on timing light has the advance and retard feature but I'm not sure where I'm starting from. If I remember correctly the standard advance at idle is 10 degrees so it stands to reason that the pulley notch is positioned at 10 degrees, therefore with my timing light set at zero when timed to this mark I'm then looking for 20-22 degrees at full revs.

Is my thinking right or have I completely miss understood what I'm trying to achieve?

The only way to do this properly is with the likes of a Sun distributer tester. moving the base timing will just offset the adv curve. IE, you may achieve your desired max adv but it would run crap every where else in the rev range. you need to change/modify the bob weights and springs to increase the range of adv and modify the curve to suit your engine. As said, you can use a distributer tester, trial and error, or do it on a dyno. Remember youre looking for the adv that gives the best power, not just a number. if you are serious about this. i would seriously consider a megajolt or other ign only programmable ECU. it will be cheaper and better in the long run as beat ifn timing is dependant on fueling. If you make changes you may have to modify it again in the future.
xxx

[steg1970]

I am planning to use MBE 967 IG when I can afford it. For now I have to use the standard set up. The car was set up at Protec in Preston, it was them who told me the distributor was not achieving max advance. I've had is refurbished and refitted but its running even worse. It's never been set up with the vac advance connected, Protec told me it was for economy only and to be fair the car has run sweetly for 5 years set up like this. Before going the 6 hour round trip to Preston I wanted to check the advance was working properly.

[meritlover]

with the timing light set at 0deg the strobe should strike the markers on the pulley and the pin.
as the RPM increases the mark on the pulley should slip back towards the bulkhead away from the pin. Adjust your timing light until the markers line up again. Read off the setting on the gun the bearing in mind '0deg' is already 10 deg.

to save the engine sitting at high RPM for too long while you mess with the gun, blip the throttle each time and make an adjustment after each 'blip' to the target RPM until the markers line up.

Ive never understood the idea behind disconnecting the vacuum. 'economy' means the engine is running most efficiently, ie. making the most power with the same amount of fuel...why would you not want this on a track car?! for the sake of connecting a tube I cant work out why people dont use it. Unless they dont understand what it does, or makes it too complicated for them to work out the timing with the gun.
If anyone can explain why this is the case then id love to know...

[steg1970]

with the timing light set at 0deg the strobe should strike the markers on the pulley and the pin.
as the RPM increases the mark on the pulley should slip back towards the bulkhead away from the pin. Adjust your timing light until the markers line up again. Read off the setting on the gun the bearing in mind '0deg' is already 10 deg.

to save the engine sitting at high RPM for too long while you mess with the gun, blip the throttle each time and make an adjustment after each 'blip' to the target RPM until the markers line up.

Ive never understood the idea behind disconnecting the vacuum. 'economy' means the engine is running most efficiently, ie. making the most power with the same amount of fuel...why would you not want this on a track car?! for the sake of connecting a tube I cant work out why people dont use it. Unless they dont understand what it does, or makes it too complicated for them to work out the timing with the gun.
If anyone can explain why this is the case then id love to know...

Thanks for that, I think I was working along those lines.

The vac advance was disconnected by Protec when the car was set up. I can't doubt what they have done as they have many years experience setting up Nova rally cars.

[meritlover]

The vac advance was disconnected by Protec when the car was set up. I can't doubt what they have done as they have many years experience setting up Nova rally cars.

no problem,

i dont doubt they have, but I've just never had a decent explanation as to why.

[meritlover]

actually, a less confusing way might be to make a new mark on the pulley at TDC but if you stick with the OE markings just remember to take the 10deg into consideration when you calculate the total shown advance.

[mowgli]

you might need to use super unleaded with a lead replacement additive to help get extra timing advance.

[steg1970]

I checked the advance this afternoon, it got to 22 degrees advance at 5000rpm. Add to this the 10 degrees and I've hit the magic 32 degrees. Took the car out and it felt sh1te! It was kangerooing and hesitating all the way through the revs. After an hours fault finding found that the Weber Alpha rev limiter was dragging it down, as soon as it was disconnected the idle smoothed out and settled at 950rpm. Took it out and it was sweet.

Roll on shakedown at Weeton in two weeks, just to sort the breather catch tank now.

[meritlover]

:thumb:
Good work