New question to an old topic, timing issues with a ZZ383.
The scenario: ZZ383 in a 40 Willys coupe. Currently using the GM recommnded HEI distributor (#93440806). Timing was 10* initial and 32* total (vacuum plugged when settings were made). Running with vacuum connected, getting 50* and pinging at part throttle in 2nd gear at about 3000- 4000 RPM. After browsing tons of forums I came to the conclusion that I have to change the vacumm canister to one that has only 10*. Does anyone out there know what part number I would be after. Any info would be greatly appreciated.
This is one of the most common subject matters that gets attention here. I/we could almost just create a word doc with some links and cut and paste it when needed. There are really 3 issues to deal with
1) base timing to get the best idle and combustion properties, usually set from 14-22 deg BTDC dependant on the cam, torque convertor, carb, heads
set through your dist position
2) mechanical advance curve (rate it comes in vs RPM) and the mech advance limit or total amount added
set through the springs that attach to the weights/plates under the rotor and the limit either through bushings or some other form of mech stop.
3) vacuum advance limit or total amount added and when it starts to come in based on vacuum pressure applied.
set with a limiter plate and the adjustment of the diaphram spring tension if so equiped, some cans do not have this adjustment.
This should get you everything you need with the exception of the mech advance limiter:
This is just the vacuum advance limiter plate
There are other things that will cause ping, one of them,,,make sure the air/fuel mix is not too lean.
I know, what I don't want to do is open up another can of worms, I don't want to start a lengthly discussion about timing, etc. When I set the initial at 10*, the total comes in at 32* and is all in by 3000 RPM (as per GM specs) with the #93440806 distributor. It seems like the mechanical advance is OK which is why I think the canister is pulling in too much advance. I pulled one of the plugs today and it is dark tan and dry. I will double check the jets though just to eliminate that aspect.
Does anyone have pictures of the proper way to mount the the limiting plate on the canister arm. I'm going to install the Crane vacuum advance canister (99600-1) on my GM HEI distributor. I am of the understanding that somebody has documented the installation procedure of this limiting plate (supposed to be mounted opposite from the way Crane instructions tell you. I will provide my e-mail address if need be.
If it does need to be installed differently to what Crane says here, it shouldn't be that hard to figure out.
Here's another link that may be helpful to you...
There is no reason to install it "opposite" unless you want the vacuum advance to come it at the same pressure that it does now and you don't have an adjustable type vacuum can (set screw inside inline with the hose nipple).
We have batted this one around before:
If you read the entire thread you will get some good ideas.
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