Novak Conversions Jeep Wrangler TJ radiator

OPDA Washer Failure Experiment

ToasterThief

Member
Original poster
Joined
Oct 20, 2022
Messages
28
Location
Utah
2006 LJ Rubicon

I replaced my OPDA with the Crown unit about 20k miles ago due to cam wear. Recently, the OPDA started to make a scratching noise so I took it apart to find the two washers had come apart and completely eaten themselves.
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Yes I know the camshaft needs to be replaced, but before I do it I wanted to change the OPDA design so it has some sort of bearing like an actual distributor since I saw others who had rebuilt their engine just to have the camshaft grenade after 5k due to a crap OPDA design. I don't know what jerk at Chrysler thought two flat washers rubbing together would be a good replacement for a bearing.

Now before you read the rest of this, keep in mind this is just an experiment. Please do not belabor me on how my car is going to explode because I'm an idiot; this is just food for thought.

I couldn't find a thrust washer with the proper diameter, so I bought a slightly small one, ground the ID down, and tack welded the outside so it didn't fall apart 😵‍💫.

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I had to make room for the larger washer, so I pressed (hammered) out the shaft from top cam index (mark the original location in regard to the shaft). I thought while I was at it I could make it adjustable so I could account for the gear wear by advancing the timing index a little. I bored out the indexer a little so I could spin it freely. I then added a thick washer and booger welded it to the shaft with three screws so I could tighten/loosen the top while it was on the car.

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The split shaft collar was so I could take the indexer on/off since the top was welder; it also let me add enough washers to set the correct preload on the thrust washer.

The OPDA hole wouldn't line up with the housing while at TDC before, but now I was able to adjust it properly to TDC (along with an OBDII scanner that let me force a relearn and read cam-crank sync status). It was pretty funny that it actually worked correct the timing because I saw the fuel trims change from -5 at idle to 0.


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This is a photo after ~10k miles of running this crapshoot setup - wear looks awesome on the inside of the thrust washer and there's no new wear on the camshaft gear. I could've made this a little better but I don't care enough at the moment. I'm not sure what the ideal is, but all I know is I'm not putting an OEM style OPDA when I rebuild this.

I don't recommend this considering it requires an OBDII scanner capable of reading cam/crank status and the potential to screw this up and destroy your engine... but I'm happy I did it. Any other thoughts or comments would be appreciated.
 
Your work is excellent. However, I thought the fundamental problem with the OPDA design was lack of lubrication along the upper portion of the shaft.
Did you try McMaster-Carr for your new thrust bearing?
 
Hey thanks! I haven’t looked at that website, maybe if I redo it down the road I’ll look more. And yeah, the crown model fixed the upper oiling issue, but I think another major problem is there’s no proper bearing to take the vertical load caused from the worm gear. My old OEM OPDA and the Crown unit had the worn thrust washers and I’ve also seen other posts with similar issues. My hope is now that it has a proper needle thrust bearing, it’ll spin more freely and cause less drag/wear on the cam worm gear.
 
Novak Conversions Jeep Wrangler TJ radiator