Timing and Dwell variations

I have a stock 71 CJ5 with a Dauntless V6 that I have had for a little over 1 year. I believe that it has about 70K original miles. The jeep has run well since I acquired it.

I recently rebuilt the carb and gave it a tune up. Before the tune up I checked the timing and dwell settings that the jeep had been running on for the past year. The timing was set at about 10, and the dwell at 34. The shop manual says that the timing should be set at 5 BTC, and dwell at 30. When I set the timing and dwell at the shop manual specs, the jeep had no power, so I set it back to 10 and 34 and it runs fine.

Does anyone know what the reasons for the timing and dwell variations might be? Any reason for concern here?? Eventually I plan on a complete overhaul, but not in the near future.

 

I'm thinking the timing chain has streched.

 

If the timing set has never been replaced, the original cam gear has nylon teeth. They were nice in cars because they are quiet, but these gears tend to shed teeth... if the gear teeth break down enough, you will jump time and the engine will run not at all or badly at best.

If you've never been into the timing cover, a steel timing set is worthwhile PM. At 70K original miles, it's probably the original set.

Can you rotate the distributor rotor much by hand?

 

Yes, I can rotate the distributor a couple of inches, but I didn't completely loosen the bolt holding the distributor. I left some tension on it so that it would hold in place while I was adjusting the timing.

 

No, how much can you rotate the rotor without loosening the hold-down on the distributor?

 

I can move the rotor about 1/2 inch clockwise. It feels like it is under spring tension, and springs back counterclockwise to its original position when i release it. It won't rotate beyond that.

 

Ok, so a worn timing chain is probably not the main issue. Replacing the timing set would still be a good idea, if it's never been done.

You are removing the vacuum advance hose and plugging the hose when you set the timing?

Does the timing mark jump around when you have the timing light aimed at it?

 

I think I'm going to go ahead and replace the timing set. I've already located the parts on NAPA online. I can get both gears, the chain, and both dampers for $52.

I am removing and the vacuum advance for the timing procedure, and the timing mark doesn't jump around.

 

Oh, I told you to do the wrong thing. Put a wrench on the crank bolt and rotate the crank forward and back. When you reverse direction, how much do you need to turn the crank before the rotor starts to turn? This will check for any slop in the chain between the crank and the camshaft. Should not be more than a few degrees.

Seems unlikely you'll find a a loose chain, since the timing mark does not jump around.

 

If the timing chain is not worn, could the issue be that perhaps the timing chain was replaced, and when it was installed the timing marks were not properly aligned?

 

Possible. Not difficult to get it lined up right though.

 

Read this, it is very well written even though it is about installing a HEI. Towards the bottom He talks about the initial timing being between 8-10 degrees. I have read elswhere that the Dauntless runs best from 8-10 deg bdc, I will try to find that article as well. Hope this helps!!

http://www.americanjeepsterclub.org/sw/hei-2.html

 

True, but its billiard table flat. So I guess we have some elevation it’s just all the same.
El Paso elevation 3740 ft.
http://en.wikipedia.org/wiki/El_paso
BTW, stay out of Juarez, I’ve heard that place has gone nuts.

 

Patrick,

How do you set this timing. Have you added marks and how do you determine total advance?

 

I must not have the same timing light.