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Original Message
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| Initial timing is irrelevant. |
| By Gerry Proctor - 04/24/2006 8:19:57 AM; IP 137.242.1.15 |
It is or will be whatever it comes out to be once you set the total.
I know it seems contrary to everything you're heard or read but it's time to expand your horizons.
First, there is no magic one size fits all initial timing number. You want 10-12 degrees just to get the car started and as a baseline. Once the engine is running satisfactorily, you can start tuning the ignition curve and total. The best way is on the track but you can do it from the seat or your pants and by ear. Optimally, you'd want to bump the total timing to the point where performance falls off, then back it down a couple of degrees. Much easier to do on the track since you have a timeslip with a MPH that you can reference.
In your case, suppose that you find that the engine makes the best power with 36 degrees total and you have a 21 degree limiter in it. That gives you an initial timing of 15 degrees. If the car ran best with 41 degrees, your initial ends up at 20 degrees. If you were to set the initial at 10-12 degrees, then you'd have to work the total with just the bushing and you may not be able to get to optimal with just a bushing. So, you can see that you want to work it from the total timing, not the initial.
It probably goes without saying that to do it right and come up with the optimum takes some time. Especially in light of trying to work the centrifugal rate into it.
Get the ignition timing sorted out before you start working the fuel curve. Ignition will have a lot more to do with how the car runs than how well the fuel curve is matched to the engine.
Holleys do run fat out of the box. It's a fact of life. You'll want to work the idle circuit before anything else. The idle circuit contributes to all the other fuel curves so whatever you do to tune the idle circuit will cascade. You'll very likely need to put a restrictor in the idle fuel feed circuit. This is usually a piece of .015" wire in the channel. Google it and you'll find plenty of online instructions on how to do this. It's pretty simple and make a big difference in eliminating or reducing the nausiatingly rich idle. Most of the time, this is about all you'll have to do to a Holley. You'll probably find the other circuits will fall nicely in line.
One thing about any carburetor and idle speed...if the idle is too high you will expose the transition slot. The transition circuit is designed to get the carb from the idle circuit to the main circuit smoothly. Yes, the accelerator pump play a part in this as well. But, if you have the primary throttle blades open too far, you will uncover this slot right above the throttle blades. Once you do this, you'll have this circuit dumping fuel at idle, which will give you a very fat idle. You avoid this by not having the idle higher than it needs to be. You can also crack the secondary a bit or if necessary you can drill air bleeds into the primary throttle blades. |
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This thread, so far...
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