ignition timing some odd readings - sorted

[Charger]

is the timeing light advance dial set to 0 for your initial at idle test?

i'ms assuming you have a "NICE" timing light, full of features you don't use...

so this is all assuming you have a gun that allows you to set advance on a car that only has TDC line and has an analogue or digital display of advance that you can adjust with buttons or knob.

don't confuse the advance and dwell displays.... (dwell is only really really usuful for points these days)

cheers Dave999, it’s a Gunson 77008 Timing Light With Advance Feature like this …



new out of the box, just has an analogue dial on the back

I started at ‘zero’ as you suggest, let’s say the index tab on the timing cover is at ’11 o’clock’, when I first pointed the light, the line on the balancer was at about ‘9 0’clock’

to get the lines line up balancer and the hole for TDC I had to turn the dial up to 20

no egg sucking here chap, just want to get it nailed, keep the ideas coming, probably me being a numpty

[Dave999]

sounds like you have it sussed

so if you measured 20 at idle
revved it ,measured it at something much more than 20

then let it go back to idle and it stayed at 38 degrees

your advance mechanism is gummed up and sticking

or you lost a spring on one of the weights and it will be MUSH in the bottom of the dizzy body by now.

However probably rust or hard grease

all the dizzys are the same, if its orginal and not australian (bosch designed advance with mopar picmkup on top) it can be easily rebuilt and is probably better quality than later MP branded stuff.

1) take off rotor
2) undo the circlip for the vacc can and loop off its lever from the stud
3) take off vacc can
4) use 2 screw drivers to lever off the reluctor star but don't loose the roll pin
5) undo the pickup advance plate
6) slip off the black triangle spring clip and take out the magnetic pickup
7) undo to 2 or 3 screws to take off the advance base plate
8) veiw advance weights and plate and springs with littl tabs sticking through the advance armature base
9) the advance armature comes off by removing a circlip under the felt pad under where the rotor was and lever it up and off.
10) don't loose metal shim and fibre washer or the circlip

clean up the weights. give their fronts backs and swivels a polish with brasso
check springs
1 has 2 tight end loops
1 has a tight loop and an elongated loop.... this is correct

put it back.

no need to take off the drive or pres the main dizzy shaft out*

1/2-1 hour job best done on the dining table on a tray

Dave


* if you do this wet n dry or emery cloth the whole shaft that sticks into the engine to clean it up and use a file to take off the burrs associated with the roll pin that holds on the drive (if you have one on a big block) the last thing you want to do is score the bushes in the dizzy base or smash them to bits

don't loose metal shims and fibre washers or the circlip that holds on the advance armature bit

Dave

[Charger]

sounds like you have it sussed

so if you measured 20 at idle
revved it ,measured it at something much more than 20

then let it go back to idle and it stayed at 38 degrees

cheers Dave, no that’s not correct, apologies if what I wrote is misleading

ignition is MP orange box + MP dizzy + Blaster 2 coil, all fitted about 4 years ago, never missed a beat

I measured 20deg at idle, but I didn’t rev it, I advanced the dizzy as Dave describes …

With the engine hot and idling, just turn the dizzy until you find that sweet spot where the rpms level off. Then re-set the idle rpm to normal (800-900rpm) and see what initial you have. The engine is telling you by the rpm where it is working most efficiently.

at this point I measured 38deg at idle

at this point I was that surprised with the readings I got I didn’t consider checking at 3000rpm

then I rotated dizzy back to it’s original position and measured 20deg again

[Dave999]

ah well

nout wrong there then...

smashin

just fit the springs and the advance limiter....

dave

[Charger]

Hi Si.....are you happy that the balancer hasnt slipped?? Could be that the TDC mark on the balancer is no longer at TDC. Maybe a rod in no1 hole and a big socket and bar to turn her over will just confirm that you are in the right area with marks

just done TDC test with rod in no. plug hole

timing marks are spot on

more tests tomorrow

[Charger]

factory groove highlighted with white paint, dots either side are stop points with rod in no.1 plug hole ...

[Dave-R]

The engine I have been doing liked 34 degrees once running as I said but for starting it liked 19 degrees best. Which is what the owner had already worked out as it happens.
So it was just a case of reducing the total down to around 34 degrees. I also fitted a lighter spring on one weight to bring the total in faster.

Adjusting the idle mixture to give max vacuum at idle and it feels much better. It was too rich.

Seems good so far. Definately feels better when you put it in gear now.

[Charger]

[cheers Dave, but this a stock’ish 383, 20deg and 38 deg at idle seems way to high to me, which is why I’m confused, I don’t want to fit the FBO limiter until I’m happy with the baseline

You sure you are on #1 plug and not #2? They are 45 degrees apart.

Try #6 and see if you have the same reading. It should be exactly the same.

cheers Dave, tried #6, same result

tried an old static timing light I’ve had for about 30 years, to at least compare, couldn’t see a blind thing, so that’s now in the bin

comparing starting/running again today from cold …

20deg – started first turn of the key, a bit lumpy at tickover until warm, 1000+rpm smooth

38deg – started second turn of the key, lumpy idle, and still lumpy at 1500rpm, I think that’s too much

I’ll get an able assistant at the weekend and get a reading at 3000rpm with 20deg initial

[Dave-R]

If it is a mild or near stock build I don't think you will need more than 18-20 initial. Make sure it starts ok from dead cold as well as dead hot.

Always adjust the idle speed to 800rpm and idle mixture to highest vacuum/rpm each time you change the initial before trying to start the car.

If it is an automatic set the idle speed and mixture with it in gear and don't forget it is in gear!

[Dave-R]

Make sure it does not continue to advance past 3000 rpm too.

[Charger]

sure Dave, will do, and thanks again

it just really threw me last weekend when I checked and it was already set to 20deg, I just wasn’t expecting that

plan is now to leave it at 20deg, hurl the limiter in on the 14deg slots and go from there

[Charger]

took the Charger out for a short run yesterday and checked timing when i got back ...

rpm ... deg advance
850 ... 20
3000 ... 37
3500 ... 41
4000 ... 41

occasionally get a little detonation at wide open throttle

will fit the limiter plate this week

[Steve]

Whats your plan Si...plate on the 14 slots??

[Charger]

Whats your plan Si...plate on the 14 slots??

yep Steve, exactly that

[Steve]

Look forward to seeing results Si...good luck matey