79 AMX Spirit 304 lessons learned

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   ahh, I know this one.  The 1406 is incorrectly jetted from the factory.  Edelbrock literature says it is 2 percent leaner than the 1405 manual choke and it is in reality 20 percent leaner.  But get the timing right first.from my notes:

Recommendation for 1406 electric choke “economy” calibrated 600 cfm Edelbrock carburetor:

Try bigger rods.  Stock 1406 primary jetting is 0.098 with 75/47 cruise/power metering rods.  The “performance calibration” on the manual choke version is 70/47, but with 100 jets, so both the cruise and full power mixture is leaner on the 1406 than what Edelbrock calls a performance calibration on the 600 cfm manual choke model 1405.  The full power is about 5.4 % richer, the cruise is an amazing 19.55 % richer.  Note that the secondary calibration is the same on both models, with 095 main jets.

For first two steps:
Try 70/42 (#1450) metering rods first.  This gives same full power as the performance calibration, still a little leaner at cruise (5% vs. 20%) than the #1405 performance calibrated carb.

To go richer still, move the 098 jets from the primary to the secondary, and install 100 (#1428) jets in the primary.  This will give approximately 6% richer primary and secondary than the performance calibration Edelbrock supplies, with the same cruise calibration as the performance carb.  

Edited by BassBoat - Mar/27/2023 at 7:58pm

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BassBoat Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1719	Post Options Post Reply Quote BassBoat Report Post Thanks(0) Quote Reply Posted: Mar/27/2023 at 7:56pm
	ahh, I know this one. The 1406 is incorrectly jetted from the factory. Edelbrock literature says it is 2 percent leaner than the 1405 manual choke and it is in reality 20 percent leaner. But get the timing right first. from my notes: Recommendation for 1406 electric choke “economy” calibrated 600 cfm Edelbrock carburetor: Try bigger rods. Stock 1406 primary jetting is 0.098 with 75/47 cruise/power metering rods. The “performance calibration” on the manual choke version is 70/47, but with 100 jets, so both the cruise and full power mixture is leaner on the 1406 than what Edelbrock calls a performance calibration on the 600 cfm manual choke model 1405. The full power is about 5.4 % richer, the cruise is an amazing 19.55 % richer. Note that the secondary calibration is the same on both models, with 095 main jets. For first two steps: Try 70/42 (#1450) metering rods first. This gives same full power as the performance calibration, still a little leaner at cruise (5% vs. 20%) than the #1405 performance calibrated carb. To go richer still, move the 098 jets from the primary to the secondary, and install 100 (#1428) jets in the primary. This will give approximately 6% richer primary and secondary than the performance calibration Edelbrock supplies, with the same cruise calibration as the performance carb. Edited by BassBoat - Mar/27/2023 at 7:58pm

rockAMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Sep/16/2011 Location: Lethbridge AB Status: Offline Points: 985	Post Options Post Reply Quote rockAMX Report Post Thanks(0) Quote Reply Posted: Apr/01/2023 at 6:59pm
	The 1406 might be lean from the factory, but it is a lot of carb for a 304. I have the same setup and actually put in one size smaller jets and rods to lean it out. It runs much better for me. Are you plugs getting fouled or do they indicate a lean condition? Maybe you have not run the engine long enough. Also agree on the timing issue. The 304 should be about 5 degrees advanced at warm idle.
	DWR 1968 AMX

jdlmodelt Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Jul/08/2020 Location: Durango, CO Status: Offline Points: 10	Post Options Post Reply Quote jdlmodelt Report Post Thanks(0) Quote Reply Posted: Apr/03/2023 at 9:34am
	what is the procedure for setting the timing on the 79 304 with the electronic ignition?

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Apr/03/2023 at 10:01am
	The timing procedure for electronic ignition on an AMC/Jeep is the same as a points distributor only you don't have to set point gap or dwell. This video is fairly good: https://www.youtube.com/watch?v=nM3LRV20l6c Only suggestion is that black marker does not show as well as something white when using a timing light. I'll take the flak again, but white nail polish works well and lasts for years. Bottle even comes with a nice fine paintbrush!

jdlmodelt Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Jul/08/2020 Location: Durango, CO Status: Offline Points: 10	Post Options Post Reply Quote jdlmodelt Report Post Thanks(0) Quote Reply Posted: Apr/23/2023 at 9:33pm
	So, found 3 foot of excess wire feeding the power to the coil so voltage was 8 volts while cranking and 10.5 volts while running. I removed the excess wire and now voltage is over 12Vdc and the engine runs considerably better. I am still getting a poor firing spark plug on cylinder 2 even though it's compression checks out good. I replaced the sparke plug 3 times and the wire once and still get a partially missfiring plug. Is this pointing toward something to do with the electronic ignition and distributor, all that are new?