kalli

Hi all,

does anyone have a reference to ignition timing.
as in

idle (800rpm) w/o vacuum advance: 12deg BTDC
idle (800rpm) with vacuum advance: 12deg BTDC

1500 rpm w/o vacuum advance: 15deg BTDC
1500 rpm with vacuum advance: 17deg BTDC

2500 rpm w/o vacuum advance: 20deg BTDC
2500 rpm with vacuum advance: 30deg BTDC

.... just as an example ,does anyone know where to get a curve for this ?

289 stock manufacturer specs would be great, or value of a car running well ...

Kalli

Starfury

I bet there's one in my Shop Manual (which you should have, if you don't already), but it's not handy atm.

Good target specs are 8-10* BTDC @idle w/VA disconnected, and 28-32* BTDC all in by 2800 or so. A more aggressive cam may require more inital timing to factor in low dynamic pressure at low rpm's.

Not so sure about VA specs.

kalli

i'll recheck tomorrow (it's the middle of the night here). I think i had weird values here.
like 30BTDC at 2000 (vac disconnected) and 40 degrees with vac connected.
I believe it's ok, as when engine is in idle, no load, needs even more advanced ignition. but still ... 40degress ???

I'll recheck and post values, as well have another look in shop manual

thx

Kalli

Starfury

30* @2k is steep, probably steep enough to require you to back off the initial timing to prevent detonation. Sounds like your centrifugal advance springs may be worn out.I know Napa carries them, but I'm sure other parts stores will as well. Check it again in the morning and make sure.

If you want to check to make sure the vacuum advance is holding vacuum, pop the cap off andhook up a hand vacuum pump to the nipple on the VA and see if it actuates the vacuum advance and holds a vacuum. If it drops, or if the vacuum advance doesn'tactuate,you need to replace it. If not, I wouldn't worry about it.

kalli

hiya, thanks for info.

I still have all the springs fro the centrifugal, 2 hard, 2 soft, 2 middle. as well the distri is new, so the Vac does work.
(i see it in my timings as well).

I'll go and measure again abnd probably exchange the springs (at least one of them) to a harder one
and try again

Kalli

kalli

have a new pertronix flamethrower distributor.
there are 6 springs (2 each), soft, middle, hard.
the distributor came installed with both medium springs.
becausethe centrifugal advance took long to kick in (1500rpm), i swapped the springs at installation
I only swapped one medium with a soft one. So now I have medium and soft installed.


the centrifugal advance measures (all with vacuum disconnected)
750rpm No centrifugal advance: 11 degrees
centrifugal advance kicks in at 1300
1500 rpm: 22 degrees
2000 rpm: 28 degrees
2500 rpm: 32 degrees
didn't go higher to not annoy the **** out of neighbours

i believe as well that this is steep, so I just replaced the soft one with the medium spring as it was on shipment.

now I have:
idle same, centrifugal advance kicks in at 150
2000 rpm: 22 degrees
2500 rpm: 27 degrees

that sounds much better to me.
Found my shop manual so I'll check if there's any reference to that now.

The car drives much smoother now as before with the different spring setup and it feels like a bit more power as well, i'm not a good judge on that.

Everyone says the engine pings when ignition is too early. I'm convinced I had it too early, but I never hear this pinging .... that bugs me ... as otherwise I'd have it much easier ....

Kalli

kalli

found the curve in shopnmanual, but doesn't make much sense to me.

they're using a test stand for it (not the engine), so they can measure speeds like 200 rpms. my advance is completely bored up to 1500 rpm ...

i have attached it anyways if someone is interested, but i'll kepp looking for real life examples. like total advance at 1500, 2000, 2500, ....


[IMG]local://upfiles/52145/5578D9BC3A0346F38E0565AFF1A2FEB0.jpg[/IMG]

Starfury

Meh...those specs are kinda watered down. Basically, they want a maximum of 20* advance (base of 6* plus 14* mechanical advance) at 2k.

Check and see where your mechanical advance tops out. The curve itself looks good, but you should have a couple more degrees of advance by 2800 if possible.