need help with vacum

[thetank]

i have a 79 CJ7 AMC 304 quad.
just finished a 6 month job of fixing the frame and the body.

got it all back together and having a problem...i think i know what it is i just dont know how to fix it.

starts easy idles perfect...but here is the problem...when accelerating it pops and jerks and back fires through the exaust.

a little of what i have done:
new magnetic pick up
new coil

i think it is over advancing apon acceleration. PO had removed most of the vacum before i got it. i have the Transfer Case and Transmission ran off of the little 2 prong adapter coming out of the back of the intake and the vacum advance coming out of the side of the carb.

Is that wrong? if so what do i do?

PO had the vacum advance screwed down in the distributer...guess he was having the same problem.

oh yeah and i reset the timing to 8 degrees

all i want to do is just hook up the 3 things...oh yeah egr is plated off too

any help would be appreciated...thank you in advance

 

[bondo258]

Can you identify your Carb and Distributor ? They are often swapped out for different models.

Has your Jeep been Nuttered? (nutter bypass for electronic carb)

Is the Dist hooked to ported vacuum? This is crucial. Manifold Vacuum works opposite of ported. You want ported Vacuum.

Locking down the vac advance is a no-no on non-centrifugal distributors. It can cause what you have described.

 

[bondo258]

V-8's of that era had a large range for the timing specs, too. Confirm what motor and dizzy you have.

Anywhere from 3 btdc to 12btdc.

Fill out your forum profile as best you can, and welcome.

 

[thetank]

i have no clue what nuttered is but the choke sensor has been bypassed and whatever that thing on the driver side is ....has been unhooked and bypassed. it has the factory dist....metal vacum advance...i pulled the screw

i ran it off of the only vacum off of my carb(i am assuming factory...ford 2 barrel) just like i do my trucks...i know it is not supposed to be ran direct off of the intake. i will take some pics later and post them for you

thanks

 

[thetank]

and i went off the book...it is running at an idle perfect...book calls for 8 and i read another post and think it is factory dist with a new pick up coil

 

[thetank]

one more thing...it is a AMC 304 i ran the numbers when i replaced the intake gasket....it has a 360 air cleaner with a bunch of vacum things on the air cleaner...do i need to use some of those
i have always just eliminated all of that...but with this problem...if i need to use them i will

 

[JR74CJ5]

Do you have a vac gauge?

What Bondo is saying is correct re: vac type (manifold vs ported)

Now I know you stated you have it running from the bottom carb vac not the manifold, but it is still possibly manifold vac.

If you have the gauge then hook it up to the outlet you're using from the carb Should be almost if not 0 when at idle. while revving (hitting gas with fingering throttle) you should see it jump with the rpm's - this is ported vac.

Manifold will do the opposite. As you rev, it lowers, and is at its highest during idle.

If you have them mixed up or something isn't working correctly, it will run like like you are describing

 

[Old Dog]

I'd also check for vac. leaks.

 

[thetank]

what is the spark cto switch...do i need it? i figured that if i didnt have the smog pump then i didnt need it

 

[thetank]

ok i finally got back to it today...it is a ported vacuum

found something out that is troubling me even more...the timing is retarding with acceleration...isnt it supposed to advance

put a manual vacuum pump on the advance and it seems to be working correctly....now i think the manual advance must be screwed up

 

[Old Dog]

ok i finally got back to it today...it is a ported vacuum

found something out that is troubling me even more...the timing is retarding with acceleration...isnt it supposed to advance

put a manual vacuum pump on the advance and it seems to be working correctly....now i think the manual advance must be screwed up

Yes it should advance.
Thats a new one on me.

 

[thetank]

when idling without the vacuum advance hooked up it sits at 8 degrees before top dead center..as i slowly rev it up it works its way slowly to 5 degrees then falls on its face and then catches itself at about 15 degrees...i am so lost

 

[bondo258]

when idling without the vacuum advance hooked up it sits at 8 degrees before top dead center..as i slowly rev it up it works its way slowly to 5 degrees then falls on its face and then catches itself at about 15 degrees

What is the condition of the centrifugal advance springs and weights?

Not sure of the Motorcrafts internals, but maybe this applies.

Can you wiggle the rotor both ways?

Does it wiggle only one way and snap back into position cleanly? Does it move smoothly? is it covered in rust?

Take the springs off, remove the plates, and wire wheel/ scotchbrite all the contact surfaces. Lube pivots with very thin layer of DE grease, (as in apply with q-tip, remove most of what you put on with the q-tip). Other greases will contaminate the rotor and cap very quickly.

Clean, lube the advance linkage, too.

Vacuum advance isn't supposed to do the job alone. Centrifugal (if equipped) does most of the work, with no load on the engine. Vacuum advance works primarily with load on the engine.

 

[thetank]

i think you were right...got into the distributer and it was all jacked up.
there were 2 different size springs and the plastic bushings that were holding the weights were trashed and they had bent it all up trying to adjust it.

just came from the parts store...ordered a new distributer and a ford cap and adapter....crossing my fingers that this is it

thanks for the help guys

 

[bondo258]

just came from the parts store...ordered a new distributer and a ford cap and adapter....crossing my fingers that this is it

Cool. remember to hit #1 TDC on the compression stroke, before you yank the dizzy, just to be safe.

I'm jealous. My HEI conversion is still in running condition. New dizzy should definitely resolve your issues.

Sounds like a previous owner tried mickey mousing it with two different springs, and the bolt through the advance.

The Joys of a CJ. Let us know how it turns out.

 

[thetank]

runs better then ever....i thought it had plenty of power before....but now holy ..again thanks for all the help guys