drifting timing (caution VERY long winded!)

[elwood blues]

A little background, I have a 1978 CJ7 pretty much stock when I bought it. Okay, it was bone stock except the seats when I bought it three years ago. Last spring I started this project. I wanted to get rid of my single barrel YF carb and I didn't want to spend the money or from what I read take the time to swap in a Weber. So, I picked up a really nice Motorcraft 2100 1.08 venturi carb. I bought a used 2 barrel intake from a 1979 CJ and I bought a brand new exhaust manifold. While I had the intake and exhaust manifold off I put in a new exhaust too, new headpipe, no cat, a flowmaster 40 and a tailpipe. I also stripped anything even remotely related to the emission control stuff. So I replaced every piece of vacuum line I could find, because now it's all different.

Did a full rebuild on the 2100, stripped it down to parade rest, replaced everything that could be replaced, power valve, accelerator pump, choke, float, needle and seat, everything. I also found smaller jets for it too. I got it all put together, had some timing issues initially, but got it all worked out and it seemed to run pretty well.

Until, the Ford Dura-spark module crapped out, again. So, I decide that I'm not going to replace that piece of junk again. After a lot of research I buy a Summit Racing street and strip ignition control module and matching coil. New Accel non-resistor plugs and new Taylor 8.2mm 4.2L specific plug wires. Plus a remanufactured distributor, new cap and new rotor. I finally got it all together and she ran. But never ran well. I never got smooth idle or drastic change in throttle response that everyone else raved about.

So, I picked up a different version motorcraft 2100, this one is an even older version. Again, full on rebuild, everything I can think of. Slap this new carb on, it still runs like crap, possibly a little worse.

Last night I finally, after the CJ's sat for close to two months, got the original motorcraft 2100 swapped back on and got her fired. It's been cold here, so I had to manually adjust crank up the idle speed to keep her running for a while. It's still running like crap, so I decide to throw the timing light on it, just to see.

As I listen to the engine idle up, then back down, shake and shimmer, darn near die, then idle back up again. I hook up the timing light, and stare down at the timing marks, in rhythm with the engine I watch the timing drifting back and forth. High idle, the timing reads 12 degrees BTDC, when it idles down and starts to shimmer and shake, I can watch the timing mark move down to probably 6 or 4 degree BTDC. Back and forth it goes, even after it's warmed up.

I'm completely and totally confused. After a session on chat here last night we came to a concensus that it's probably something with the vacuum advance, or a vacuum leak. If anyone else has a good idea, please let me know, I'm pulling my hair out.

P.S. If it counts for anything, I have a distinctive valve-train (I'm pretty sure it's a lifter) ticking noise. Funny thing is, as you adjust the timing more or less BTDC, the ticking noise comes and goes.

[BajaEdition]

ok, I am out of my element here, I do not know much about a 78.
But. first let us GET TO BASICS, plug the vacuum line to the dist,, and see if she will run without the variance. We are checking to see if it is the distributor. if it does run now, with no wobble, we now go and get the motocraft instructions and check each vacuum port for where it goes. We need to see if everything is sucking correctly. once checked, we try again, After this, I would need to be there, I think the advice of someone else here would be prudent

[LongHorn]

IMHO "Baja" is on the right track. Do you know the history on the short block?

[elwood blues]

Got it, back to basics. Stop nuking this, it's no where near as complicated as I'm making it out to be


I don't understand Longhorn, "do you know the history on the short block"? Are you asking if I know the history of my particular vehicle, or the 258 engine in general?

[LongHorn]

Originally Posted by elwood blues Got it, back to basics. Stop nuking this, it's no where near as complicated as I'm making it out to be I don't understand Longhorn, "do you know the history on the short block"? Are you asking if I know the history of my particular vehicle, or the 258 engine in general?

I was talking about "Nylon Timing Gears".

[elwood blues]

Originally Posted by LongHorn I was talking about "Nylon Timing Gears".

I know absolutely nothing of "Nylon Timing Gears".

[LongHorn]

Originally Posted by elwood blues I know absolutely nothing of "Nylon Timing Gears".

Your 258 came from the factory with "Nylon Timing Coated Gears".
A 1/8" or so thick coating of nylon that over time wears out cracks & falls off. letting your timing chain slip, changing your timing.

[Old Dog]

The timing should be changing with the RPM's, thats what it does. The question is, is the timing making the rpm's change or is the timing changing because the rpm's are changing.
I would make sure you don't have a vac. leak to begain with. Do the basic timing and such to see if it will smooth out.
I was also having a problem somewhat like that when I found the bad bushings in my dist. You might want to check thoes out also.

[Petescj]

Wouldnt that at some point throw the whole motor out of time enough to stop it and be unable to restart?

Originally Posted by LongHorn Your 258 came from the factory with "Nylon Timing Coated Gears". A 1/8" or so thick coating of nylon that over time wears out cracks & falls off. letting your timing chain slip, changing your timing.

[elwood blues]

Originally Posted by Old Dog The timing should be changing with the RPM's, thats what it does. The question is, is the timing making the rpm's change or is the timing changing because the rpm's are changing. I would make sure you don't have a vac. leak to begain with. Do the basic timing and such to see if it will smooth out. I was also having a problem somewhat like that when I found the bad bushings in my dist. You might want to check thoes out also.

The distributor is "new" remanufactured unit I got from NAPA, can't be more than 4 months old now. Think a got a bad refurb unit?

Originally Posted by Petescj Wouldnt that at some point throw the whole motor out of time enough to stop it and be unable to restart?

I was thinking the same thing.