Another timing curve question

Thanks, I may try the distributor recurve before digging into the carb. I can get a Mr. Gasket 925b spring at the local O-Reilly so I'll use that for the light one.

I don't recall the slots being grossly different in location, but now that you mention it... I'll eventually be removing the carb from the manifold to install setscrew-type idle air bleeds, so can look closely at the t-slots then. (It's an old 4780 double pumper for someone who's better acquainted with the fine details than I am).

The faster idle is needed because the cam is 312 advertised, 272 @.050, 107 centerline, in at 105, and that along with lots of idle timing is what it wants. Helps with cam/valvetrain oiling too, although that's a feature, not a bug ;) I would be very surprised if anyone could get a stable idle with this cam at 800 or 900 in a carbed 451, especially with the hefty electric fan load kicking on and off... Everyone who ran one of these says it idled best at 1100-1200.

I don't know the "proper" positioning of the secondary t-slots either, so assumed it should be square like the primary. Which still wasn't enough air without adding 3/32 holes in all four blades :rolleyes:

It idles much better (and with the butterflies more closed) at 30 degrees, but then the engine won't start when hot. I am wary of start retard units and want to keep the teeth on my starter and ring gear...

Anyhow, if I get my advance curve set up for, say, 28 at idle with a long slow slope to 36, I will definitely be able to close down the secondaries somewhat (and may even have to solder the drilled holes shut). All this interactive fuel/air/timing is giving me a headache! :realcrazy: