I agree with Bewy, in both posts 3 and 12;
My 11/1, alloy-headed 367/4speed, likes more than 46* at 65=2250 for cruising; and up to 60* at 65=2800. This was about the same, with all three cams that I have run in it; from
[email protected] to
[email protected]. The trick I used, to fire the lean cruise, is to install a hi-amperage coil.
>You should be running a PCV system; I use it as part of my Idle-Air bypass. Your cam will want a lot of bypass air at idle. This will likely make it go lean with applied throttle and rpm. You gotta fix that.
>If you are running a Multi-Strike, they switch over to single-Strike at about 3000. IDK what happens if you cruise on the switchover; try cruising at say 2900 rpm.
>Here's how you can tell how much cruise timing that you should entertain:
1) during this test, you will try to maintain your cruise rpm by adjusting the throttle. If there is a V-can installed then hook it up. You say 3000, so rev it up to 3000!
2) Leave the timing lite in the tool box. Without any regard to the actual timing; just pull a little advance in, and return the rpm to 3000. Then pull a lil more in, and return the rpm to 3000.
3) keep doing this until more timing produces EITHER;
a) no more rpm, or
b) a loss of rpm. If this happens, take a lil timing out.
4) NOW, you can put the timing lite on her and check the timing at 3000rpm.
5) whatever you get, subtract THREE degrees, and write the number down. This final number is your target cruise timing.
6) put the timing back to your start point, and return the V-can's status.
>For reference only, here is my curve;
.78degree per 100 rpm, beginning at around 900, and ending at 3400, for a total of 20 degrees.
The initial on mine is 14*.
I run a ported V-can that is modified to deliver 22*, ASAP.
If you add that up it only totals 56* @3400, lol.... but I cruise at 2250 in overdrive. Which is 14 initial plus 10.5 mechanical plus 22 vacuum =46.5.. This is NOT ENOUGH for optimum fuel mileage, so I installed a dash-mounted, dial-back, timing module with an adjustable range of 15 degrees. I set it in such a way as to allow 6 additional degrees for cruising; so 46.5 plus 6 equals 52.5.. This is still not optimum for long-distance touring, but there's up to 9 more in that module.
>BTW-1
>If you try to run more than about 18* at idle, I can
almost guarantee you that your throttle will not be up the Transfer slot far enough, and your mixture screws will be too far open, to compensate for the lack of fuel coming from the transfers.
>If you try to run the Vcan off manifold vacuum AND in conjunction with 18*plus initial, for something like 31* plus at idle; I guarantee you that the transfers are too far closed. Furthermore; I don't think you can get enough fuel out of the mixture screws to make this idle decently AND,
this situation usually creates a fairly substantial tip-in sag, that is usually not possible to cover with pump-shot. And as soon as the engine gets over the sag, it goes pig-rich from the wide-open mixture screws.
Reset the mixture screws to in the middle of their range, and supply the missing idle-fuel from the transfers. Then reduce the idle-speed by subtracting timing. Bewy mentioned this when he said to reset your T-slot exposure to .040, which is underneath the primary throttle blades.
>When I ran that 249* cam, my 750DP ran best with the Secondaries closed up tight,(but not sticking) and the Primary throttles both drilled with one hole each, on the T-slot side, of 3/32 to 7/64 inch. These holes have the advantage of reducing airflow with increasing throttle, to better control the AFR when on the primaries. Whereas cracked secondaries IMO are a less desirable way, and in my combo instantly ran worse with no solution.
The 223 cam did not require any Bypass air, so I soldered the holes shut.
The 230 cam is more or less ok with no Bypass air, but she seems ok with 1/16 holes, one in each primary blade. Any more is worse.
>BTW-2
Now that you have your cruise-timing figured out, here's how you figure the cruise-fueling; this is for a NON-metering rod type carb :
1) set the mixture screws into the center of their range.
2) Rev it up to 3000rpm and fix the the throttle there.
3) Screw the mixture screws in, until the rpm begins to drop, then back them up rich 1/4 turn; this is your starting point.
4) if the rpm does not drop, the circuit is already too rich.
5) if the mixture screws need to be enrichened beyond the center-point, then the circuit is already lean
6) fix it. this usually involves changing the air-bleeds, but could include changing the WET fuel level, or the minimum coolant temperature, or the Inlet air temp.
>BTW-3
What we are doing here is determining a starting point. Right now; the car is stationary with the hood open, and the engine is NOT seeing the same conditions as when actually cruising with the filter house on and the hood closed. So; the carb may have to be tweaked as time goes by.
BTW-4
if you have a drop-base filter house, I have no experience with those except to say that it is possible for the bowl-vent, to get up too close to the lid, and mess up the signal to the bowl, which messes everything up.
edited for grammar, spelling, and clarity.
Happy HotRodding
