Help! Engine Tuning

[Doug_3B]

Alright guys, I am so frustrated with my 3B - I just can't seem to get it tuned right. 

My setup:  1963 CJ3B with the F134 engine.  Pretty stock.  Complete rebuild in 2012, only have 4-5k miles on it since then.  It ran good, but always seemed to run rich.  I'm running an alternator, a Carter YF that I put a zip kit in around the time of the engine rebuild, and I don't have the oil bath air filter, I have the K&N canister connected to the air horn on top of the carb.  In the course of troubleshooting, I sent my distributor off to be tested/rebuilt and there was so much wrong with it that it was going to cost so much to repair that I could by 2-3 new distributors.  I probably made a mistake by buying a new dizzy, but I still have the old one that can be rebuilt at some point.  The new points style dizzy is currently installed in the engine. 

I found the procedure to tune the engine using the vacuum method by ScoutPilot.  I was excited to try it and get my engine tuned right.  Some of the issues I run into:  with the idle stop screw 3 complete turns in, I'm running at about 1400-1500 RPM.  At this point, I have about 18 Hg.  When I start to back off the Idle stop screw, absolute best vacuum I get is 19 Hg.  When that happens, she's still running at 1100-1200 RPMs, so adjusting the idle mixture screw does nothing.  I even thought maybe I had a crappy vacuum gauge, so bought a second one to be sure.  No change.

I've checked/adjusted valves twice.  Replaced the distributor - points are set really close to .020", but dwell is around 44; it's about the closest I can get it.  The cheap points mounting plate in the new distributor does not have the adjustment eccentric screw, so I probably adjusted them 15 times today and this was as close as I got.  Over the last year, this problem flustered me and I started throwing money at it.  I put in a new fuel pump and line from tank to pump (Walck's kit).  In addition to the new distributor, I also got a NOS Carter YF carb from India and put that in.  I think that new carb may have issues, so I have my original back on.  New plugs, and a Flame thrower coil on it because I was planning on swapping to a Pertronix.  New points, condensor, cap and rotor all came with the new distributor.  I have new wires to put on it, but have not done that yet.  I know better than to throw money at a problem and change out a bunch of components and I did it anyway.

Today, I decided to go through Section C in the Service Manual, paragraph by paragraph.  I didn't get all the way through it, but probably half way or so.
I did the compression check (all plugs out, choke and throttle wide open)
#1 - First crank 60 psi, 4th crank 110 psi
#2 - First crank 70 psi, 4th crank 110 psi
#3 - First crank 70 psi, 4th crank 105 psi
#4 - First crank 70 psi, 4th crank 110 psi

Pretty consistent if nothing else.

So, I poured some oil down inside the cylinders and rechecked
#1 - First crank 80 psi, 4th crank 120 psi
#2 - First crank 80 psi, 4th crank 120 psi
#3 - First crank 80 psi, 4th crank 110 psi
#4 - First crank 70 psi, 4th crank 120 psi

If I understand the manual correctly, this low reading on the first crank and building up pressure indicates cylinder wall/ring wear or valve adjustment.  That's why I added the oil like the manual said, to narrow down between the two.  It improved it but only slightly.  Does this indicate valve issues?  I've checked valves twice now, using the opposing valve method. 

I'm not hoping that I have valve issues, but if I do and correct it, I'm then hoping my vacuum readings improve and maybe the rest of the tuning procedure works.

What do you think?  Am I on the right track?  What else should I be looking for?  What have I left out to complete this story?

I worked on it for probably 4 or 5 hours in 100+ degree temps today.  It's now running decently; although idle is about 1100 RPMs.  It's the first time in probably a year that I'd chance a run around the block.

I did time with a timing light and had it idling at around 600 - 700 RPM, but still not sure it was correct.  The idle adjustment screw on the carb seemed like it was way far out - 3 or 4 turns something like that.  The timing light fell down and went through the fan today, so I'll be without one for a week or so.  Another thing I noticed when using the timing light, it seemed like it had a periodic miss where I didn't seem the timing mark on the pulley; I'm guessing it's because the light didn't strobe.  Crappy timing light or it didn't pick up the current in the wire - bad wire?

Thank you for any help in advance!

[PercyUK]

Hi Doug, I'm sure you know what your doing but when you refer to the idle adjustment do you mean the idle mixture. In my experience it is far to far out. It meters the fuel and once you get to the sweet spot the revs are unlikely to change further regardless of how many further turns you add. The idle speed is set using the idle speed screw. I would get a fast idle using the idle screw then wind the idle mixture in until it falters then slowly back it out until it is revving as fast as it can smoothly. Once you notice that there is no further change then stop. Further turns will just make it rich with no gains. Then drop the revs to your preferred idle speed using the idle speed screw. Sorry if I'm stating the obvious

[scoutpilot]

I'm confused. What, exactly, is the idle RPM right now? What, exactly, is the vacuum reading?

Okay. So you installed a ZIP Kit. The whole kit ,or just some of it? Did you check the throttle shaft for runout? It should not wiggle at all. Your statement concerning the Idle Mixture Screw setting at "3 or 4 turns something like that..." tells me you may have a vacuum leak. Does the motor need choke applied to run?

[Doug_3B]

I appreciate the replies guys.  Sorry for the long post above; I was out in the heat all day and fed up.

Hi Doug, I'm sure you know what your doing

We probably shouldn't assume that Percy! LOL  You're right, that is way too far out.  And, that was with the new carb that I had on there.  I put my old carb on and we're right about 1-1/2 turns out from bottom.  And making the idle mixture adjustments, it works exactly as you said in your post:  back it out to a certain point and there are no more gains.

I'm confused. What, exactly, is the idle RPM right now? What, exactly, is the vacuum reading?

OK, I have my old carb back on there that I put the Zip kit into.  As far as I know, I put the whole kit in there, but it's 10-12 years ago.  I did not do anything with the throttle shaft, or bushings, or anything like that.

I went back out tonight and with the old carb on there, things seem pretty good - at least a lot better than I've gotten it to run in a long time.  However, idle is still way high, and I seem to have a slight miss.  Idle is at 1000 - 1100 depending on if you believe my dwell/tach/volt meter (1100) or the tach in the cab (1000).  However, vacuum at this point is probably the best I've seen at 20.5 in Hg.  If I back the idle stop screw out any more to lower RPM, I really start to lose vacuum and it becomes erratic.

[scoutpilot]

Does it require choke to idle?

[Doug_3B]

For initial start up yes.  After a minute or two she'll idle fine with no choke.

[1955CJ-5]

Hi Doug,

You may have already done this but I learned from trouble shooting on the Model A engine that one of the things commonly done, is to short each spark plug to ground briefly, one at a time, and see how the engine responds to having one cylinder not firing.  If all cylinders are firing equally then the engine should slow and run rough each time a plug is shorted. If one plug is shorted and very little change occurs then that might be your problem cylinder, as it's not contributing much. If all cylinders respond the same then it's something common to all, fuel delivery or a bad condenser maybe.

All this really does is narrow down the search but it's quick and easy and might help.

Another thought is that the advance weights might be sticking in that new distributor.

My '55 had low compression on #1 but we ran a hot spark plug in it for a while and it eventually improved. It had been sitting for quite a while so maybe running the hotter plug and allowing the cylinder to fire loosened whatever gunk was in there.

Randy

[scoutpilot]

Finding the balance between the air (vacuum) and fuel mix can be tricky. Always it is best to start with the book settings. Three turns in for the steel idle stop screw and 1.5 to 2 turns out from a light bottom for the brass (sometimes steel) Idle Mixture screw. Adjust as necessary to get it to idle. Let it warm up.
Watching your Vac and Tach gauges, alternately and incrementally adjust each as necessary to increase the vacuum and lower the idle RPM.

[PercyUK]

Hi Doug, just a quick question. Did you resolve the timing light issue when it occasionally failed to fire? I am chasing a misfire on my cj3a and have noticed that my strobe does the same and can't decide whether it's connected. I have replaced all the ignition in an attempt to locate it so far without result. Ta.

[scoutpilot]

https://oldjeepcarbs.com/thread/29/time-motor-timing-light