Nutter bypass timing curve

primezero · 10-15-2009, 06:31 PM

I have read a few threads about the timing curve after the nutter bypass is done. What I got out of them is that since the computer controlled a lot of the timing, the timing curve isn't as big as it should be and that new advance springs should be installed or a distributor from a jeep that didn't come with the computer stock. I was going to buy a new distributor and do the team rush upgrade and since I already have the nutter bypass done I was wondering if I should get a distributor made for an earlier cj.......is anyone knowledgable on this subject?

**swatson454** · 10-15-2009, 06:58 PM

Yes you should. Otherwise you're stuck with roughly 8 degrees of centrifugal advance which is really just a "limp mode" type setting. I went through the same thing and it makes a pretty big difference.

primezero · 10-15-2009, 07:38 PM

so a distributor made for a cj prior to 82 would work good?

**swatson454** · 10-15-2009, 07:44 PM

From what I've read '78 should work well. Should have an 18 degree slot in the head which will give you more room to adjust with weights and spring combos.

83cjnut · 10-15-2009, 08:20 PM

Ummm, don't forget about the vacuum advance that you get from the ported supply on the carb going into the distributor.

I'm a newb to most of this as well, but it seems that you have two factors at play, both the mechanical advance from the physical action of the distributor parts spinning and then you add the gradual ported vac advance the carb provides above idle.

Not saying it isn't there or that it won't work (i'll leave that to the experts), but I have not seen anything about a requirement to use an older distributor after nuttering.

primezero · 10-15-2009, 08:41 PM

I just ran across it in another thread. My vacuum is hooked up, I just heard the computer advanced it more being the third factor to advance it, and that had to be made up another way since that is what the engine was designed for.....I just wanted to see if it was just that one person that thought that, or if it really should be done.

83cjnut · 10-15-2009, 08:58 PM

Check this thread:

http://www.jeepforum.com/forum/f8/how-nutter-bypass-522262/

This has the steps needed to complete the bypass. Note from my sig that I haven't done it yet, but is supposed to stop raining on Sunday and I will do it then (no garage).

I have no plans to replace the existing/stock distributor. Again, not saying it won't work the same/better with an older distributor, I just don't know about it. If someone did it, it worked, and you want to spend the money for a new "old" distributor, tally ho. After all, that's why we are here - to try new stuff, see if it works, report back to the group, repeat.

primezero · 10-15-2009, 09:45 PM

I suppose I will just check the full advance on my dist. Looks like after reading through many of the forums that the mechanical tops out at 13-18 advance from initial and with the vacuum connected the full advance should be around 33-35. If I have that, I will just stay with the same type of distributor.

Tortured · 10-16-2009, 04:15 AM

Full advance on my stock distributor is 40* BTC at 2800rpm's. The problem I do see is it's only 20* BTC at 2000rpm. A Chevy motor would be almost at full advance at those rpm's. It would be nice if someone chimed in with actual hard numbers and let us know what rpm's full advance should hit at on these motors. And yes my jeep is Nuttered.

**swatson454** · 10-16-2009, 09:01 AM

http://www.jeepforum.com/forum/f8/centrifugal-advance-recurve-814305/?highlight=Recurve+distributor

That's a link to a post from months ago. It has my actual centrifugal numbers after recurving my dizzy. It works extremely well set up this way. Hope it helps.

Fjguercio · 10-16-2009, 12:45 PM

Swatson is correct,, once nuttered on the 82+ Jeeps there can be improvements with the advance. The computer can take out advance so the advance in many cases is very high. That is why the computer years typical start with more advance.

We have done this here on JF a dozen times this year 2009.... so there are some excellent posts.. We have also posted the distributor curves for the PReComputer Jeeps and the Compter Jeeps. The precomputer years have more advance on the chart/graph.

There is a difference with the DISTRIBUTOR advance limit slots..... ONE THING we need to do is measure the advance slots with a caliper so we can change the old distributors to the widers slots..... So when you are in there measure the slots with a caliper and the stamped number. With some posts and people keeping track we can possible modify or attempt to modify the computer dist to have wider advance slots and then stamp the corrected number on there. This would save the $50 to buy a remanufactured 1978 or 1979 or 1980 Distributor to get the larger slots.... Sooner or later the supply of larger slot distributors may run out.... guess on my part but makes sense.

This is a fairly involved process, but the results are good. You can also buy a fancey MultiSpark Ignition Modual and they can add and change the advance curve too.

so search it up there are much better ones than the one MR Swatson posted there.

Fred

PS
JeepHammer is the expert on this..... so search for the words or search his posts to find the good ones... I have posted on a few of them too.

**swatson454** · 10-16-2009, 12:51 PM

Ease up on the hero worship, stud. I've been doing this a long time too and have had dyno operators scratching their heads wondering how I got so much out of it.

Fjguercio · 10-16-2009, 01:11 PM

Quote:

Originally Posted by swatson454

Ease up on the hero worship, stud. I've been doing this a long time too and have had dyno operators scratching their heads wondering how I got so much out of it.

Nothing about heros... I went and read YOUR THREAD, the link you provided above, and yes it is about the DuraSpark Distributor.... There are much better posts on this subject, with pics that will be needed when the reluctor is removed, if the larger slot is used there are changes that need to be made to distributor, and some of the posts have a dozen pics.

IMO there are much more informative and much more detailed posts on this subject. Follow your post/thread you put the link for and I bet 9 of 10 JeepForum Folks get it wrong.

I just do not have time to look for the better posts..... so I mentioned they are they and they should be searched. I have participated on most of the other threads too by the way.... so I do have some understanding too.

Regards to you,
Fred

**swatson454** · 10-16-2009, 01:16 PM

That was the only post I could think of right off hand too. No worries

crzdmnky · 10-16-2009, 01:28 PM

All I did was the bypass, and hooked the Dist. Advance direct to the carb., and turned the timing where it ran good and didnt overheat.... Just like you would do on any other older vehicle. Havent had a problem, its not a race car your dealing with, or some high performance machine needing to perform at extreme conditions all the time. Thats my take.

10-16-2009, 04:15 AM	#9
Tortured Registered User Join Date: Jul 2005 Location: Las Vegas Posts: 167 Profile Gallery Classifieds My Jeeps	Full advance on my stock distributor is 40* BTC at 2800rpm's. The problem I do see is it's only 20* BTC at 2000rpm. A Chevy motor would be almost at full advance at those rpm's. It would be nice if someone chimed in with actual hard numbers and let us know what rpm's full advance should hit at on these motors. And yes my jeep is Nuttered.