re-learning

[balldeboy]

Hello everyone, I recently upgraded my AMC 258 i6 / 4.2l I-6 with an HEI distributor. I got the distributor from CRT performance and have been trying to get a response from them for almost 2 weeks and they won't answer me. The distributor is installed and the Jeep runs great until I plug the vacume advance in. It is timed, installed and wired correctly. The distributor comes with an adjustable vacume advance. I have never dealt with this before so I don't know if that is my problem. As I said, the Jeep runs great until I plug the vacume advance in. I have a Carter BBD carb. Any advice or ideas will be GREATLY appreciated. Thank you all very much!

 

[CJ]

What is the timing and RPM's without and with the vacuum advance line plugged into the dist (don't forget to plug the line when checking timing)?

Do you have a vacuum gauge? Plug it into the vacuum advance line going to the carb at idle. You should see no vacuum (if you do see a vacuum your advance port is not working correctly or you have it plugged into manifold vacuum and not ported vacuum). Start to rev the engine, the gauge should progressively show more vacuum. If you show no vacuum then the advance port is not working.

Do you have a vacuum pump (if not - you can just suck on a vacuum line)? Connect it to the dist and slowly apply a vacuum, with the top off you should see the cam move inside the dist. If it doesn't move and you cannot apply a vacuum then the diaphragm is torn. If it holds vacuum but nothing moves (does not advance the timing) you have a stuck advance assembly.

Post back your findings.

 

[balldeboy]

The RPM is 1600 and the timing set at 8 degrees advanced, The vac. advance line is plugged while I'm setting the timing. Something I just thought of was the "nutter bypass". The installation of this distributor requires the 1st half of the "Nutter Bypass". The 1st half is the rewiring between the distributor and the ignition box under the over-flow tank. The 2nd half of the "Nutter Bypass" is the connection of the vacume advance to a different place on the carb. Should I try this? Here is a link to the installation instructions for the distributor. 258 HEI instr.. Thank you very much CJ!

 

[CJ]

I'm nut sure about the bypass as I have never worked on one or researched it.

But, 1600 is way to high. You would be pulling ported vacuum to the dist at 1600 rpm's. You need to set your initial timing at about 750 rpm's then hook up the vacuum line. Then the timing should not move.

 

[balldeboy]

Thank you very much! I will give that a try.

 

[Kane]

Proper initial timing requires you to disconnect and plug the ported vaccum, turn the idle down down to 750 or less. Then set your initial advance to what ever your engine requires (8degrees TDC). Adjust the idle to proper rpm (750) in this case, then hook up your vaccuum advance. The idle should not change at this point. Ported vacuum will not affect the distributor until you start revving the motor. Now your adjustable vaccuum advance will need to be set for total advance. This is a combination of idle, mechanical and vaccuum advance. If you have 8deg idle, 25deg mechanical (the little centrifugal weights)that will give you 33 degrees total Mechanical advance. Now your vacuum can be set according to your target. I am not sure what the AMC 258 i6 / 4.2l needs for total advance. In my case with a chevy motor it is 38 degrees. So I would set the vacuum advance to 5 degrees. That is accomplished by adjusting the screw inside the diaphragm on the vacuum pot. This will limit the stroke. Go ahead and rev the motor over 2000rpms with the timing light in use and see where you end up. If it is too high then go ahead and turn the screw in, if too low turn it out and try again until you get it right. I haven't had to do this in awhile so hopefully I explained it right. It sounded good in my head anyway. Also if you do not have a timing rule on your harmonic balancer that goes to 40 degrees or more you need to buy one. They sell timing tape in Summit and Jegs. this will help you tremendously for setting total timing.

 

[balldeboy]

Thank you very much!