Jumped timing

I have a 70 Cj-5 with the dauntless V6. Besides taking the water pump off and timing cover, how can I tell if it jumped a tooth. I know I can take the valve covers off and see if the valves are closed at TDC but will that be accurate enough?

 

Clean up your front cover timing marks. Pull your plugs, grab a flashlight so you can see the piston moving up/down on #1........turn motor over slowly by hand clockwise and watch the valve action. After the power stroke the exhaust opens & closes then the Intake opens & closes the next stroke up will be compression and then the next time the front hub lines up with the 0 zero mark on the cover that should be TDC. A few degrees before TDC your motor should have already fired off #1 cylinder. The Piston should be at the top of it's stroke and you are correct both valves should now be closed................ The rockers & push rods should be relaxed on #1 although on hydraulic lifter motors that does not me loose as in lash would be on a solid lifter motor! Pull your distributor cap a see where the rotor points to.........Should be pointing to the #1 plug wire on your cap.............if your rotor does not point to #1 and you have verified all of the above............then your valve to piston timing is off and one can assume that the timing chain has jumped a tooth or is just loose..................Now is this a motor that you have just had apart or had the distributor out of?

 

I never had it apart but I did have the prestolite distributor rebuilt and replaced it back without turning over the motor. It ran lousy and backfired bad. I think it might have jumped time. It's definately not 180* out.

 

Those odd fired Distributor's can be tricky once out and then put back in.........easy while sticking them back to not get on the correct lobe , also the rotors can sometimes be confused with the even fire rotor , resulting in just what you talk about above. Do a search on this site it has been discussed and written up here several times..........also check on line. Plenty to look at........Once you have determined that you are on the correct lobe then proceed to check TDC and see if the rotor is pointing to the correct position on the cap. If it ran OK before I suspect it's in the phasing of the distributor..........if this motor is new to you and you were trying to correct misfiring by fixing the distributor then it could have jumped a tooth.

 

I've had the jeep for 30 years and haven't driven it much. I decided to get a rebuilt because the vacuum adv. was shot. It started easy and ran fine though. The new distributor has play in the shaft, some of the lobes are .016 and some are .018 point gap and the timing mark jumps around so I returned it and am looking for a HEI. I want to check the timing chain so I don't damage the valves when I fire it back up and am going to take the valve covers off and see what I can before taking the rest of it apart.

 

It would have been much easier to do the TDC and valve to piston timing check if the Distributor was in the correct location and had been running OK.............since that's not the case go back to what I said earlier.........valve cover off ,rotate motor ,exhaust open and close, Intake open and close next time your mark on the crank is at 0 zero........... peak in the spark plug hole and see if the Piston is at TDC and the two valves are closed.....while peaking in the hole while moving the crank back and forth you can see where TDC is when the Piston seems to stall at the top of the stroke while slightly moving the crank..............that will be true TDC......... if the marks on the cover do not line up, and or the valves are starting to open you have issues, if the mark is only off a few degrees up front that should be fine and that is just a little sloop in the chain...............get the distributor in correct and..............Fire it up!

 

I don't have a feel for how easy/hard it would be to detect jumped timing chain using the method tarry described - I know it would work but I don't know how long the valves stay closed so I doubt that I would be able to tell.

I would for sure try to see if the timing chain is loose by rotating the crank back and forth using the front nut while looking at the distributor rotor. If you can rotate the crank back and forth without the rotor moving then the chain is really loose and needs to be changed regardless if it's skipped a tooth. If the chain is not loose at all then it probably didn't skip. When my chain was loose it made the typical noise of slapping the inside of the cover.

As mentioned, I think it's more likely something with the ignition timing rather than valve timing. When I recently pulled the distributor I got it put back in wrong several times before I finally got it correct.

good luck

 

The chain must have slop in it because when I do rotate the crank the dist. rotor doesn't move for a while. 10* OR MORE. I'm going to change it when I get around to it.