Lean idle. Rich cruise.

Ok, back to your timing. But first we need to talk about your power curve, whatever that is. I’m pretty sure you posted the numbers but even if you did post the curves I wouldn’t remember the details.

To that end, I’m not surprised it wants all that timing at low rpm. That’s because the fuel coming from the carb isn’t “prepped” correctly by the time it gets to the chamber.


You want to atomize the fuel at the booster. Vaporize it as it gets to the chamber and when it’s on the chamber.

A tightly packed chamber with with fully vaporized fuel will have the quickest, cleanest burn time. Hence, you can run less timing which reduces working losses.

When the carb isn’t doing its job for whatever reason, and especially and specifically when you are using a cold air intake (or even worse yet a tunnel ram) you don’t have the heat to help vaporize the fuel.

All that conspires to force ignition timing to compensate for poor carburation.

The goal should be (talking NA here) to speed up the burn rate as fast as you can so you can reduce timing.

If you can fire the plug at 30 degrees BTDC you will make more power than if it timed at 40 degrees BTDC as long as the burn is mostly done by 12-15 degrees ATDC.

Doing so reduces negative work on the crank.

Back to your curve.

If you look at your dyno sheets you can see where peak torque is and where peak power is.

So you have 3 points on that graph that you must account for when developing the timing curve your engine wants.

You have your minimum idle speed, peak torque and then peak power.

I’m not getting into initial now because you get that. What concerns me is what’s happening at peak torque and then what’s happening at peak power. Because the timing requirements are far different at peak torque than at peak power.

Most engines (evidently yours at this time doesn’t follow this) want LESS timing at peak torque and MORE timing at peak power.

So thinking that through when you lock out the timing you are killing one point with too much timing and the other with not enough timing.

Why is your engine different when the build is similar to many others?

Because your carb is sending a fuel/air mixture that isn’t as good as it should be. And you are correcting that with timing rather than fixing the carb and putting a curve in it.

It’s much more work to fix the carb and start over but the end result is worth it.

When you fix that carb you’ll find out it won’t want that much initial as you have when it’s locked

I’m just guessing here but from what I remember your engine will want (as a start) 20-22 degrees initial, 24-26 at peak torque and 32-34 total, depending on rpm. If you are shifting higher than I remember that total number could and probably will be higher.

And since you’ve been screwing with the timing I can assume you understand how much work it is to get a curve in the distributor.

Along those lines, with the stiffest springs you could only delay the timing to just over 4k.

That has to be at or even before your torque peak. Which means you are killing power at peak torque from too much timing and killing peak power with too little timing.

I can say that most of this could have and should have been worked out on the dyno. It’s damn hard to do in the car and even harder if you are trying to do it with a timing light rather than a test bench.

When I start out on the dyno I lock out the timing. Then I make some pulls to find the best power with the timing locked out. Then I do a series of tests where I vary the load and rpm and then vary the timing at those loads and rpm to develop the curve.

Once I get all those numbers I head over to the test bench and get to work.

I spend many hours just getting the curve in shape. It can take forever especially when peak torque is a long way from idle speed. You have to delay the start of the curve sometimes and you might need custom springs to do it.

In fact the heaviest springs that MSD and everyone else sends out aren’t strong enough for most anything.