Help me understand timing after nutter bypass please - JeepForum.com
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post #1 of 17 Old 01-18-2016, 06:13 AM Thread Starter
bucs1fan
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Help me understand timing after nutter bypass please

I have a general understanding of timing but little confused after the nutter bypass. I completed the nutter bypass and now want to set the timing. You clamp the vacuum line from the distributor warm up you engine to idle temp and set timing to 8 degrees? Before I set to 8 should it already be set to 0? If not how do you set it to 0 first. Just need it cleared up. Thanks

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post #2 of 17 Old 01-18-2016, 06:19 AM
Matt1981CJ7
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Set what to 0?

If you are talking about Top Dead Center (TDC), you don't have to worry about that unless you pulled the distributor.

Just unhook the hose at the distributor and plug it. Then set the timing.

Matt


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post #3 of 17 Old 01-18-2016, 06:26 AM Thread Starter
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Ok just set after the bypass got it, thanks. It says something about using a T adapter for the vacuum line coming out of the distributor to the carb, where does the other new vacuum line go?
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post #4 of 17 Old 01-18-2016, 06:45 AM
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What Nutter directions are you using?

I wouldn't T the distributor with anything. I would connect it straight to manifold vacuum, either at the carb or the intake manifold.

Matt


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post #5 of 17 Old 01-18-2016, 06:45 AM
Mike Romain
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Quote:
Originally Posted by bucs1fan View Post
Ok just set after the bypass got it, thanks. It says something about using a T adapter for the vacuum line coming out of the distributor to the carb, where does the other new vacuum line go?
You sound like you need to read it better. The ported signal also feeds the EGR via the CTO and the charcoal canister purge signal.

Mike
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post #6 of 17 Old 01-18-2016, 06:48 AM Thread Starter
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Quote:
Originally Posted by Matt1981CJ7 View Post
What Nutter directions are you using?

I wouldn't T the distributor with anything. I would connect it straight to manifold vacuum, either at the carb or the intake manifold.

Matt
http://www.4x4wire.com/jeep/tech/ele...jn-ignition99/

Disconnect the vacuum line going to the distributor and plug the port that the it originally went to. Now attach the disconnected vacuum line from the distributor to a tee that you will have to install in the the ported vacuum line. The ported vacuum line is attached to a fitting on the BBD carburetor located on the side towards the valve cover, about 1/2 way up the carb.
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post #7 of 17 Old 01-18-2016, 06:49 AM
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Here's the vacuum layout I'd use after the Nutter.

Matt
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CJ-7 Vacuum Routing - Post Nutter Bypass.jpg  


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post #8 of 17 Old 01-18-2016, 06:51 AM
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Quote:
Originally Posted by Matt1981CJ7 View Post
What Nutter directions are you using?

I wouldn't T the distributor with anything. I would connect it straight to manifold vacuum, either at the carb or the intake manifold.

Matt
Unlike Matt, lots of us like to have the timing advance jump up when you hit the throttle so we use ported vacuum as per the nutter directions. John Nutter also preferred it this way. The emissions sniffer also appears to like ported vacuum better.
It makes for a jumpy throttle response off the line.
Some, like Matt, prefer manifold vacuum. That gives a nice slow smooth start when you tromp it.

Mike
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post #9 of 17 Old 01-18-2016, 06:53 AM
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Quote:
Originally Posted by bucs1fan View Post
http://www.4x4wire.com/jeep/tech/ele...jn-ignition99/

Disconnect the vacuum line going to the distributor and plug the port that the it originally went to. Now attach the disconnected vacuum line from the distributor to a tee that you will have to install in the the ported vacuum line. The ported vacuum line is attached to a fitting on the BBD carburetor located on the side towards the valve cover, about 1/2 way up the carb.
Yeah, I wish those directions would go away.

No CJ ever came from the factory that ran straight ported vac advance. None, zero, nada. And, despite what others will tell you, there is no difference in take-off performance between the two vacuum signals.

That's all I will say, because this subject always turns into a pi$$ing match.

Matt


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post #10 of 17 Old 01-18-2016, 06:59 AM Thread Starter
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Ok well thanks for the help Mattt... I appreciate it
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post #11 of 17 Old 01-18-2016, 07:16 AM
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Quote:
Originally Posted by Matt1981CJ7 View Post

Yeah, I wish those directions would go away.

No CJ ever came from the factory that ran straight ported vac advance. None, zero, nada. And, despite what others will tell you, there is no difference in take-off performance between the two vacuum signals.

That's all I will say, because this subject always turns into a pi$$ing match.

Matt
And you accuse me of misdirection... Some 258's came set up to use ported vacuum once warmed up and manifold only when cold. They also came set up using ported all the time unless it heated up over something like 220F, then it only ran manifold to help it cool down.
The ECU era 258's used manifold advance, but the ECU had 100% control of the timing advance signal.

Mike
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post #12 of 17 Old 01-18-2016, 07:34 AM
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Sorry all, I just can't let this misinformation prevail.

Quote:
Originally Posted by Mike Romain View Post
And you accuse me of misdirection... Some 258's came set up to use ported vacuum once warmed up and manifold only when cold.
Yep they did. And these CJs didn't display the jumpy and smooth throttle response that you claim. In fact, when they switched from manifold to ported, there was no difference in performance other than a lower, weaker idle on ported.

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Originally Posted by Mike Romain View Post
also came set up using ported all the time unless it heated up over something like 220F, then it only ran manifold to help it cool down.
Wrong. The heavy duty cooling option, started out on manifold when cold, switched to ported when warm, then switched back to manifold above 220*. And, again, these signal switches didn't cause the CJ to change from "smooth" to "jumpy", as you claim.

Quote:
Originally Posted by Mike Romain View Post
The ECU era 258's used manifold advance, but the ECU had 100% control of the timing advance signal.
Wrong again. If this were true, then why even have the vac advance? It would serve no purpose. The truth is, the vac advance acts independently of the computer.


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post #13 of 17 Old 01-18-2016, 07:41 AM
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OP,

The Nutter Bypass directions are incomplete, in my opinion. Although it fixes a jacked-up carb problem, it also completely hamstrings the timing curve. If the instructions were complete, they'd tell you that your next move would be to either install an advance head from a pre-computer distributor or lengthen the slots in your existing one.

That's why we keep having this pissing match over ported vs manifold vacuum. If you choose to get that deep into it, I'd give serious consideration to the "Stealth HEI" mod.


Shawn

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post #14 of 17 Old 01-18-2016, 09:23 AM
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Quote:
Originally Posted by Matt1981CJ7 View Post
Sorry all, I just can't let this misinformation prevail.

Yep they did. And these CJs didn't display the jumpy and smooth throttle response that you claim. In fact, when they switched from manifold to ported, there was no difference in performance other than a lower, weaker idle on ported.

Wrong. The heavy duty cooling option, started out on manifold when cold, switched to ported when warm, then switched back to manifold above 220*. And, again, these signal switches didn't cause the CJ to change from "smooth" to "jumpy", as you claim.
Matt in those cases it gets switched to "up" the idle speed so it runs better in certain situations as you well know.
What does that have to do with the fact they ran ported normally? Just more misdirection?
We are talking both of the advances being set at idle. One no advance, one full advance.
Quote:
Wrong again. If this were true, then why even have the vac advance? It would serve no purpose. The truth is, the vac advance acts independently of the computer.
Matt, you can't tell me that there wasn't a difference in the throttle response off a start when the idle speed jumped way up once it was switched to manifold vacuum, then dropped to normal speed on ported. Try it yourself.

The OP is best to just try both because there " is" a difference in the throttle punch on the 258 and 4.0 engines set up with the nutter no matter what your 360 does or what you think.

My butt doesn't lie to me.

The stock signal wires also all go to the ECU and the ECU has 100% of the timing control to the point it can even retard just one cylinder if it feels a timing knock. A timing knock can be from too much vacuum advance too Matt....

Mike
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post #15 of 17 Old 01-19-2016, 01:29 AM
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The technical manual for the MCU states it can indeed retard ignition when it feels a knock on one or more cylinders via the knock sensor but there is one aspect that has always puzzled me.

The amount of ignition advance supplied by the MCU is stated to be governed by engine speed, with the sensor in the distributor being used to provide a tach signal. The mechanical advance head in the distributor provides up to 6.75 degrees of advance, the MCU provides the rest. But why does the MCU not do the whole job, what is the purpose of having a limited mechanical advance?

I agree with the sentiments stated above, if you want to have the ignition timing correct you need to do some work to the advance head as the MCU is no longer adding advance based on engine speed.

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