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I posted in the bronco forum, it is under "timing issues". My question, is untill I can regear, I can advance my timing to a TOTAL of 48 deg at 2800-2900 RPMs. It will run a lot better and can keep up with traffic this way, but is that too much advance? Yes it is hard to start, but I can use an ignition box with a start retard feature.
Are you checking the timing with the vacuum advance disconnected?
Not for total advance. I disconnect it for initial, then hook it back it up. When I do total advance at 3000RPMs, the vacume is gone, and only the mechanical advance is engaged. That is where I got a reading of 48.
If you're getting 48° with just mechanical advance, that's a lot, for sure. You sometimes can get there if you throw vacuum advance into the mix, too. But If your vacuum is 0, and your timing is at 48 at 3000 RPMs, you're throwing a lot at it.
When PerformanceDistributors curved my HEI distributor, they told me to put it at 12° base timing.
Then it had 22° of mechanical advance.
At 500 RPMs it added 0, and then gradually increased to 22 at 2750 RPMs.
500 was 12° total (12 + 0)
1000 was 18
1500 was 25
2000 was 29
2500 was 32
2750 was 34 (12 + 22).
The vacuum advance added in up to another 14° when there was high engine vacuum (low load).
This could get it up to 48° of total advance (12 + 22 + 14) but only under very light load. The engine vacuum had to be 13hg or more.
Vacuum advance started coming in around 9gh. Anything less than that and the vacuum advance was 0, so timing was purely base + mechanical.
If you're getting 48° with just mechanical advance, that's a lot, for sure. You sometimes can get there if you throw vacuum advance into the mix, too. But If your vacuum is 0, and your timing is at 48 at 3000 RPMs, you're throwing a lot at it.
When PerformanceDistributors curved my HEI distributor, they told me to put it at 12° base timing.
Then it had 22° of mechanical advance.
At 500 RPMs it added 0, and then gradually increased to 22 at 2750 RPMs.
500 was 12° total (12 + 0)
1000 was 18
1500 was 25
2000 was 29
2500 was 32
2750 was 34 (12 + 22).
The vacuum advance added in up to another 14° when there was high engine vacuum (low load).
This could get it up to 48° of total advance (12 + 22 + 14) but only under very light load. The engine vacuum had to be 13hg or more.
Vacuum advance started coming in around 9gh. Anything less than that and the vacuum advance was 0, so timing was purely base + mechanical.
I ordered an MSD box with the start/retard option that way I can run more advance and still be able to start it. I am loosing all vac advance once i use the accelerator. I am curious to see if using a "T" and to join the man vac and carb vac to see if that helps.
Yeah, that's one thing I really like with my Sniper setup.
I have about 20° of timing at idle, but when during startup, it's only 4°. It rips to life when I start it.
How do you have your vacuum advance hooked up? It should just be a vac line going right to the manifold (or the ported vacuum on the carb).
You're running 48° and not getting any pinging?! How??
i used a dial back timing light. Vac advance hooked up and on the throttle.
could be the engine is just too worn out to ping. Blow by?
it is in the middle of rebuild now so ill update when motor is back in.
i used a dial back timing light. Vac advance hooked up and on the throttle.
could be the engine is just too worn out to ping. Blow by?
it is in the middle of rebuild now so ill update when motor is back in.
The total timing needs to be checked with the vacuum advance disconnected.
You may think there isn't any vacuum at 3000 rpm in neutral but you may be surprised.
The total timing needs to be checked with the vacuum advance disconnected.
You may think there isn't any vacuum at 3000 rpm in neutral but you may be surprised.
my question would be why? If the vacume is connected while your driving and hit 3000 RPMs, wouldnt you want a real time reading? Or does a load on the engine change that?
my question would be why? If the vacume is connected while your driving and hit 3000 RPMs, wouldnt you want a real time reading? Or does a load on the engine change that?
Yes, the load on the engine changes the vacuum conditions.
Real world timing is WOT at 3000 rpm.
You cannot hold WOT at 3000 rpm in neutral standing at the vehicle with a timing light.
To accomplish the same conditions, you disconnect the vacuum advance line and then check the timing at 3000 rpm.
That is the way it has always been done.
My carbed efi headed 300 can't have more than 2° base and 26ish total mechanical advance and forget about the vacuum advance it just causes extreme pinging. I assume this isn't not normal, anyone else have this issue with a points distributor?