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Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

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post #1 of (permalink) Old 11-01-2007, 08:13 AM Thread Starter
 
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I am back did you miss me, few tech questions

Okay here we go, I have done the hei/mc2100 swap.I have the timing set at 6 degrees before top dead center, plugs gapped at .055, carb mix screws set at 2 turns out, got a vaccuum gauge to it and pulling good vaccuum.
The rod that hooks in front of the carb with 2 A & B notches and goes to the side of the carb with 4 hole settings. How do youll have this set?
1.My problem is that it idles pretty darn good, and has good power, but under hard acceleration, it has a hesitation/miss in it.I tried to lean it and it didnt work so to rich it out more neither helped me.
2. Other problem is I need to adjust the kick down. I have no idea here and all my buddies have no experience with automatics so.......Is the hesitation from the kick down? What is the process to adjust it, I think I have an idea because it looks easy but just want to be sure......
3. last problem Okay while I was finishing up my tuning last night, I went to crank it up again and I have no fire.......I checked the power to the distributor and I have 12V....I checked the ground on the distributor and 12v...I hooked up my timing light adn tried cranking and no strobe....pulled number one plug grounded it to the block turned over, no spark....Could I have dropped a pickup in the distributor???? How do I test this...It is a new cap and rotor button.

Wow I wrote alot......thanks in advance everyone!
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post #2 of (permalink) Old 11-01-2007, 12:26 PM
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Well...glad to see you didn't pack it in and give up....

Ok...first the HEI...how did you buy it? Already set up? The pickups almost never go out....it's a simple coil (or Hall effect) and magnet. The most common problem with them is that people will remove the electronic module off the dist plate, wipe the grease off and put it back on dry....that grease is a special thermal compound that helps remove the heat from the module...without it the module will burn up.

Hesitation...how did you hook up the dist advance? The HEI vac advance is opposite the stock jeep...it's been awhile since I had mine so I can't remember where it goes....

Kick down - I'm assuming you have an auto...there is no real adjustment...you just need to confirm that the kickdown is basically at the low pos when the throttle is at idle and at full open when the throttle is full open. Actual pos is not real critical. Make sure the vac modulator is hooked up properly.

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post #3 of (permalink) Old 11-01-2007, 12:40 PM Thread Starter
 
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yeah i bought it used. Can I just buy another module and grease at the auto parts store or is this special order? What kind of grease is it?

The vaccuum advance I have running to the side of the carb because I was thinking you dont want a live all the time vaccuum on your advance, Is this correct?
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post #4 of (permalink) Old 11-01-2007, 02:43 PM
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I believe the module comes with a small tube of the grease...check the box when you get it....BTW...I would suggest getting it from NAPA and use your AAA discount....

There are two types of dist vac advance...Manifold and Ported.

With Manifold advance, at idle or high vac conditions, you have maximum advance...as you open up the throttle, the advance retards to reduce the chances of knock...but then the advance springs kick in and advance the timing as needed for the given RPM.

With ported advance, vacuum increases as the velocity down the carb increases (more throttle)...hence, little or no vac means max advance and at full throttle min advance...with the advance springs once again adjusting timing based on RPM.

I believe the HEI is connected to Ported vacuum (someone correct me if I'm wrong). I just know it's the opposite of the stock Jeep dist.

Anyway...I think you can see why FI is so much better than the old Carb and vac advanced dist....it's easier to fine tune the timing with a computer vs. springs and vacuum.

AKA DDawg16
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post #5 of (permalink) Old 11-01-2007, 03:14 PM
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Dawg - Not to argue - but:
Direct manifold vacuum has not been used since the 30's. But there are lots of them around where someone got it mixed up!
Vehicles that use it only use manifold vacuum as a power source. Those are supposed to have solenoids or switches in that vacuum line - the sensors and/or computer operates those switches to turn it on and off.
Manifold vacuum itself has a curve that's not the curve the engine requires. Kinda similar under some conditions, but not close enough.

For instance YJ's - they used manifold vacuum through 2 solenoids that inhibited advance unless it was in high gear and at cruise speed.

Some folks think they are doing good when they bypass those solenoids and run manifold vacuum direct, but it runs worse!

The trick - find the PORTED vacuum source, connect it directly to the distributor, then set initial timing to 8 degrees (I believe factory says 17 at 1800? But that's because it uses manifold vacuum with solenoids.)

It makes a huge difference when you give the engine the spark advance that it really needs!

The no spark condition - start with the most likely - the center of the rotor cracks and flashes though to ground.
Next most likly - remove the coil and look closely at the ends - if you see grayish marks like smoke, it's gone!
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post #6 of (permalink) Old 11-01-2007, 03:35 PM Thread Starter
 
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Thanks....I will check that in a little bit and get back with you.
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post #7 of (permalink) Old 11-01-2007, 06:30 PM
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Quote:
Originally Posted by JeepDawg View Post

Kick down - I'm assuming you have an auto...there is no real adjustment...you just need to confirm that the kickdown is basically at the low pos when the throttle is at idle and at full open when the throttle is full open. Actual pos is not real critical. Make sure the vac modulator is hooked up properly.


Since the timing and vac issue seems to be well in hand I'll just add my 2c to the kickdown issue. I have an auto in my 7 and if I recall the kickdown does need to be properly adjusted or you stand the chance of doing damage to the tranny. What that damage is escapes me as I sit here in my easy chair, but I do recall it being an issue, at least according to the haynes/chiltons I used.

I'd advise shelling out the $20 for the manual and give it a bit of investigation. A good investment anyway and a cheap bit of insurance that the OP doesn't breeze past something that might bite him later. The worst that can happen is I'm full of it.
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post #8 of (permalink) Old 11-01-2007, 08:28 PM
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I'm not for sure but I think that kickdown rod changes pressures in the tranny. I was told if it's too loose it can let the trans slip - that's the damage.

Too tight it's constantly downshifting when you don't want it.

Maybe a transmission expert can shed some light on it?
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post #9 of (permalink) Old 11-04-2007, 07:53 AM Thread Starter
 
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alright I got my timing strait, now under half throttle it seems the carb is starving for fuel??? Is the stock fuel pump big enough to feed the mc2100? What kind of pressure should I see ?
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post #10 of (permalink) Old 11-04-2007, 11:01 AM
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Yes. The stock pump has plenty of capacity. The 2100 won't take much more than any other, because the amount of gasoline the engine uses is proportional to the amount of air the engine can inhale, and you haven't changed that much if any.

Per the '78 FSM, when all engines were carbureted, pressure for all sixes should be 4 to 5 PSI, or 5 to 6.5 for V8s, which used the 2100. Your problem might be improper jets in the carb, or it could be unrelated to fuel problems. How does it run at full throttle? If OK, it's not a supply-related problem.

EVERYTHING's easy for the guy who doesn't have to do it.
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