Pinging on acceleration.
The only way to know the advance curve (unless its an unmolested dizzy with its original tag) is to measure timing at increasing rpms.
A way to do sortof cheat it without timing tape or a dial back light is to set timing at some timing above such as 1000 rpm.
(and yet another option with a smogger distributor is to set it at 0 and then try using a manifold port for vac advance)
Even with a 1973 distributor, the timing by 1800 rpm should be about the same as a non-smog 1967 225 distributor.
At what RPM ?
It is critical to know the rpm. You can get TDC on the timing light, and then get 5* on another occasion without touching the distributor just because the engine was more warmed up or the idle speed adjusment was messed with.
With a non-smog distributor, advance may begin as low as 600 rpm.
For example: Using the 1967 225 w/o CAP distributor, measuring 10* at 900 rpm is the same as measuring 5* at 550 rpm.
Second example, lets use the 1973 distributor which is probably closer to the magnetic pickup distributor being used here.
Using the middle of specs for that distributor, setting it to 10* at 1000 rpm is the same as setting it to 5* BTC at 550 or even 700 rpm.
That might be OK, or might ping a bit on longer trips when accelerating.
Setting it to 10* at 750 rpm, would put it around 32* by 2000 rpm and like Dan was saying, that would not be good for a daily driver.
Same concept as covered in post #14
The point is no one knows what the advance curve is in Witchboard's distributor.
But even so, it is important to know the rpm of the initial setting. One guy's slow idle is 500 rpm and another guy's is 1000 rpm.
I agree with Dan. As a blanket statement that's not quite so. TDC will work OK with a fast advance that was used in the early smog distributors.
The only way to know the advance curve (unless its an unmolested dizzy with its original tag) is to measure timing at increasing rpms.
A way to do sortof cheat it without timing tape or a dial back light is to set timing at some timing above such as 1000 rpm.
(and yet another option with a smogger distributor is to set it at 0 and then try using a manifold port for vac advance)
Even with a 1973 distributor, the timing by 1800 rpm should be about the same as a non-smog 1967 225 distributor.
At what RPM ?
It is critical to know the rpm. You can get TDC on the timing light, and then get 5* on another occasion without touching the distributor just because the engine was more warmed up or the idle speed adjusment was messed with.
With a non-smog distributor, advance may begin as low as 600 rpm.
For example: Using the 1967 225 w/o CAP distributor, measuring 10* at 900 rpm is the same as measuring 5* at 550 rpm.
Second example, lets use the 1973 distributor which is probably closer to the magnetic pickup distributor being used here.
Using the middle of specs for that distributor, setting it to 10* at 1000 rpm is the same as setting it to 5* BTC at 550 or even 700 rpm.
That might be OK, or might ping a bit on longer trips when accelerating.
Setting it to 10* at 750 rpm, would put it around 32* by 2000 rpm and like Dan was saying, that would not be good for a daily driver.
Same concept as covered in post #14
The point is no one knows what the advance curve is in Witchboard's distributor.
But even so, it is important to know the rpm of the initial setting. One guy's slow idle is 500 rpm and another guy's is 1000 rpm.