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Unread 05-25-2002, 01:25 PM   #1
TG CJ7
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Join Date: Jan 2002
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Nutter Bypass question

I finally got my brothers jeep started today. On a previous post, it was suggested that I try the Nutter bypass to see if the ECM was malfunctioning. It was, the jeep starts now. My problem is that I’m confused on the last two steps of the operation. What exactly do I do with the vacuum line that is connected to the distributor? And how do I set my timing (I have a timing light). I would appreciate any comments from anyone who has done the Nutter Bypass.
Thanks
Tim

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Unread 05-25-2002, 04:15 PM   #2
johny1i
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You'll probably get an even split of opinions when it comes to sources for the vacuum advance, but I chose to stick with stock manifold vacuum. I can only set my advance to about 8-deg at 800 rpm (which equals about 15-deg at 1600) because any more and mine will ping in 5th (with 89 octane gas). If you have a four-speed, I'm sure you can go higher because even at 10-11 degrees (at 800 rpm), I wasn't pinging in gears 1-4. Just keep a careful ear for the first few days. With manifold vacuum, there is about a 7-degree difference between 800 rpm and 1600 rpm (which is where my hood sticker says the engine should be timed at). I just don't like working next to the fan when it's spinning that fast, so I set it at 800. And oh yeah, make sure that the vacuum line is disconnected from the distributor and plugged when you are setting the timing. If you want to try ported vacuum, you'll have to talk to some of these other guys because I haven't done it--I like the curve that comes with manifold.
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Unread 05-27-2002, 12:59 PM   #3
Woodbutcher100
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I have a similar question involving a Webber carb on a 1980 258 cj5. It has been lacking power, stumbles when I give it full throttle and has a ping, I am trying to set the timing right. They have you attach the advance to the carb base and warn not to vary from the specified porting. I just rebuilt the engine and replaced all the guts including a custum cam shaft, valves, springs and put in a strieght pipe exhaust. I think it is at 10 degrees now and ran better a twelve. I also think I may have the rong size jet in the carbureter. How do you set the ammount of advance and what should it be?
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Unread 05-27-2002, 04:01 PM   #4
johny1i
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It is easy to tell if that weber vacuum source is ported or manifold (I know some carbs can put ported right at the base and fake you out)--if it has any vacuum at idle (without the throttle valves open), it is manifold. Ported vacuum will be zero at idle and only develop as the throttle is opened. I'm not pretending to be any kind of expert on this stuff, but if you put in a new cam, you could have easily increased the compression in your engine and affected the proper timing considerably, so I wouldn't necessarily say that there is anything wrong with 12-deg (or more) if your engine is running well with a lot of advance. The pinging may be the result of using too low-octane gas if the engine is now producing more compression. The difference between 87 and 89 on mine would amaze you, and you may need at least 91. Stumbling can also be an accelerator pump adjustment problem within the carb, so make sure that it is adjusted as best as possible. My carter had a terrible flat spot just off idle until I got it just right. Don't know if this stuff will help--just my 2 cents. Concerning jets, I know that some motorcycle carbs have to be rejetted when they go to straight pipes to keep them from running too lean (hot) and bluing the pipes (my little bro ran into this on his Softail), but if you have anything more than header/scavenger pipes, etc., you should have enough backpressure to not have to worry with that. When you say "straight pipes", do you mean not even a muffler? I guess on a CJ5 with no muffler and those short pipes that exit by the door openings, maybe you could be a little bit lean--don't know that one for sure.
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Unread 05-28-2002, 11:45 AM   #5
Woodbutcher100
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Thanks allot for the info. I noticed that the timing changes considerably when I take of the vacume advance and plug it. It obviously has vacume pressure at idle or there would be no change. I'll try to move it to the manifold and see what happens. Thanks again.
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