If there is a potential benefit and you can drive something else while
you do it I can understand the desire; I can rarely leave well enough alone :)
This is a b21a with Zenith, right? A cam? Grimshaw recommends a heavier
cam for performance IIRC. To me, the beauty of the b21a is that it is
apparently designed solely for reliability; the fact that it goes is
almost incidental to the fact that it keeps going.
Smallest bore and compression of the 240s (unless a b19 was equipment - same block?), lightest cam, low pressure mechanical fuel pump, rather low horsepower but really twisty.
Since I just want to get where I'm going (and back) I don't much mind that the car is a plodder. Everything is done right on it.
The power does everything required, safely, and the balance of the total design is one of the most enjoyable aspects of a 240.
I look forward to hearing about any modifications. Watching the tennis I am reminded of pleasant car-working weather. It is cold as Hades here, but a b21a is fine in the cold :)
--
Stef - 81 245 B21A M46 319000km "fat chrome" roofrack

Both distributors achieve full advance at around 3500 RPM. From there they are the same and that's where you make power. Centrifugal weights always err on the conservative side, and they are simple to the point of archaic, so a few degrees either way as they achieve full advance is not going to matter at all.

I agree with Mike. If you get detonation you can certainly adjust the initial
advance to greatly reduce or eliminate it and it should not affect overall
driveability.
Also every job you do on a distributor entails some risk. Given the choice of
using the distributor as is, even if the curve is different, and making
major conceptual changes in its operation, I'll vote for "as is" every time!

--
George Downs Bartlesville, Heart of the USA!

You guys may be talking apples and oranges.

If you are keeping the "A" setup: cam, carb., exhaust; then keeping the "A" curve would be most effective.

If you are altering the cam, carb, exhaust, etc. for increased flow/performance then the "A" setup will severely limit your output (may even make it worse than it would have been "stock").

On the other hand, a factory engine is a compromise of parts assembled under more-or-less controlled conditions to satisfy a large number of customers. These parameters leave much to be desired in the performance category.

I think you ought to try the "E" setup first. If you don't get detonation you will likely get more pep. IF it doesn't help or you don't like it you can always build it into an "A" as stated.

--
Mike!