Hang on;
We are not there yet.
First we gotta make it idle.
Ok so, I'm assuming;
Part-1
1) that the engine temperature is 185 to 195degrees, and that you are at 1000ft elevation or less, and that the choke is wide open.
2) that the WET fuel level is correct for the carb.
On that Holley with the fixed fuel sight-windows; IIRC this should be half way up the windows. But I don't know that for a fact, so check it out.
3) that the transfer slot exposure under the throttles is about square
4) that the mixture screws are set to about 3/4 turn out from lightly seated
5) the Ignition timing is in the range of 10 to 16 degrees at Idle, with the Vcan defeated and that it does not change when you reconnect the Vcan to ported spark.
6) idle speed is about 550 in gear and
7) it does not increase by any more than plus 100/150, on the shift into neutral
8) for your cam; the 20-212-2, with 268/268/110Lsa advertised, and 218/
[email protected]; the idle-vacuum is likely to lower than expected so Ima guessing about 15"inches to maybe 13. This is a guess, and could vary with your actual settings, especially the timing. It does not matter what it actually is so long as the engine is NOT getting any unauthorized air; it is only a point of reference.
9) I don't care about the fuel-pressure if it idles at a fairly steady rpm and does not flood itself to death.
If that is NOT what you got STOP! me now.
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If that is what you got, then we can continue.
Part 2a
1) With engine warmed up and at idle, note the exact rpm, then stuff a rag into the Secondary side. This should affect the idle-rpm very very little; unless your carb has a 4-corner idle system.
2) assuming that you do NOT have a 4-corner; if the rpm changes more than 50 rpm, then very likely the secondaries are not closed, so fix it. Sometimes you have to bend the Secondary link-rod, sometimes there is a secondary cracking screw. For this 218*cam, the secondaries should be closed.
Part 2b
1) With engine warmed up and at idle, note the exact rpm, then using a rag, begin to restrict the primary air supply, by covering the airhorn.
If the AFR is exceptionally lean, the rpm will rise.
If the AFR is exceptionally rich, the rpm will fall immediately as the engine floods.
If the AFR is normal, the rpm will drop, but slowly, as the engine goes rich.
2) depending on what your engine does, it will point us towards what to do.
3) keep in mind that
at idle, the fuel supply to the engine is a joint venture between the Idle mixture screws AND the Transfer-slots, so it is real easy to make the engine happy ...... or not, by varying ONE or the OTHER supply. If the idle speed changes during making her happy, then we change the Idle-speed using Ignition timing.
Part-3
1) In Park; rev up the engine to in the range of 1800 to 2000rpm or thereabouts and put the throttle on the nearest fast-idle step; exact rpm not important. Next; close the mixture screws lightly, and make sure the rpm goes down. Then open the mixture screws until the rpm peaks or the adjustment is more than 1.5 turns with the rpm still rising; this should not happen.
2) If it does, then the transfers are lean. The rpm should peak with the screws at from 1/2 to 1.0turns out from lightly seated. Put the screws back to 3/4 turn and kick the throttle back to idle, and let her cool off.
3) if the transfers are too lean, we have to figure out why, and fix that.
4) if the mixture screws behave normally, then you do not have a vacuum leak and we can continue.
Part-4
After you get the above business sorted out;
1) lets look at opening the throttle. The first few degrees are handled by the transfers. If you have a tip-in hesitation, which is; a moment in time that the rpm hangs, falters, or decreases, during SLOW opening of the throttle, we have to fix this. With the mixture screws properly set, likely the transfers are ever so slightly too far closed. Remember, this event occurs before the accelerator pump can respond, and it happens with a slow opening of the throttle. You have to fix this before moving on; because the pump can never eliminate this and when it happens, it is extremely annoying.
2) after that is fixed; make sure your accelerator pump squirts fuel the very instant that you open the throttle blades more than just a few degrees. Sometimes you have to bend the link-rod, or eliminate slack in the system, or change tuning parts.
3) During this hammer-down throttle-application, the ignition timing will have to immediately keep up. If your timing curve does not begin to advance until say 1600rpm, then you will have problems. Ideally, from idle, the timing should only have a small period (like 200/250rpm), of no activity. By 1000 rpm the timing should begin to advance. And the rate of advance should be about .70 to .80 degrees per 100rpm. Thus by 3600, the timing should have risen to between
(3600 less 1000idle)/100 x (.60 to .80) =16* to 21* over the base; AND it should in
no wise be more than 36* in total, including your base idle setting. Not all engine combos will allow a total of 36*@3600; keep that in mind.
At WOT and say a 2200stall you should be looking at about
(2200 less 1000)/100, times say .7 = 8.4* plus the base of say 16=24.4*
The thing about all this is to give your engine as much timing as she wants, but not one degree more, and to keep her always always out of detonation.
Below stall, the engine does not really care much what the timing is because she never has to pull (work hard) down there. So, at this time, I wouldn't spend too much time on that part of the curve.
However, the more timing that she is able to handle down there, the nicer she will respond to throttle-inputs. In other words, lazy timing = lazy throttle-response. This has ALMOST nothing to do with a tip-in sag or a bog; and I have never cured either of those with more timing.
Ok so, that will keep you busy for a while, right now I got some things to do before it gets dark.
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