2005-06 Jeep OPDA_CPS_Distributor Failure - Page 111 - JeepForum.com

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post #1651 of 5484 Old 07-20-2011, 11:25 AM
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Originally Posted by speed_phreak View Post
OK OK OK, fine... maybe I will try to limit my pissing away of dollars on this heep... Thanks for talking me down.

So, what do you guys think about taking a new cam in to get just the OPDA gear mesh hardened. Is it possible to just harden that gear on the cam without effecting the rest of the cam? I'm just thinking about long term survival of the cam now... I suppose I can change OPDA gears like I change oil, but can't do the same for cams. I am willing to do it once, but only once!!!
Check out TJJP77's adventure with that question a few pages back. He did the cam without pulling the head & did a great write up with photos.

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post #1652 of 5484 Old 07-20-2011, 11:47 AM
Heath
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Do not replace a flat tappet cam without replacing lifters. The risk is not worth the reward.

You might as well not replace the cam at all.

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post #1653 of 5484 Old 07-20-2011, 07:56 PM
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Originally Posted by Rubi4MyMrs View Post
Check out TJJP77's adventure with that question a few pages back. He did the cam without pulling the head & did a great write up with photos.
Yea, I don't think I am up for that... I am going to bite the bullet and pay someone to do it right for me... I want the lifters done too...

BUT, I want to know if anyone has ever heard of adding extra hardening to just a portion of a cam. In this case the OPDA pinion gear portion. Is such a thing possible? Will it mess with the tolerances?

I want to buy a stock 4.0 cam and send it somewhere to have the OPDA pinion gear hardened to protect it better than stock. With me? Done this? Possible? Good idea? More trouble than it's worth?
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post #1654 of 5484 Old 07-20-2011, 08:35 PM
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Originally Posted by Heath View Post
Do not replace a flat tappet cam without replacing lifters. The risk is not worth the reward.

You might as well not replace the cam at all.
I disagree. I have enough hours on my engine to be confident that there are no ill effects. Would I try it if the vehicle had 80,000 miles on it? No. But with a mere 12,000 miles, I wasn't concerned based on advice I got from people who tear down and evaluate engines for a living.

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post #1655 of 5484 Old 07-20-2011, 08:38 PM
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Quote:
Originally Posted by speed_phreak View Post
So, what do you guys think about taking a new cam in to get just the OPDA gear mesh hardened.
The gear is already hardened. All wear surfaces on a camshaft (the lobes, bearing journals, OPDA/distributor drive gear) are surface hardened several microns into the metal. The core of the camshaft needs to remain soft and ductile to keep the cam from becoming too brittle and fracturing.

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post #1656 of 5484 Old 07-21-2011, 12:50 AM
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Quote:
Originally Posted by TJJP77

I disagree. I have enough hours on my engine to be confident that there are no ill effects. Would I try it if the vehicle had 80,000 miles on it? No. But with a mere 12,000 miles, I wasn't concerned based on advice I got from people who tear down and evaluate engines for a living.
Glad it worked out good for you. Any engine builder will tell you do not do this. I have personally seen several instances where people swapped different cams in hot rod motors without swapping lifters, to their demise.

Heavy springs and big cams compound the issue, but it's still there.

You replace a cam so the new gear on the OPDA won't start a odd wear pattern, but you leave the old lifters in the motor, not caring if they start a odd/bad wear pattern on the new cam? Did I assess that correctly? Does that make sense? Why do any of it?

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post #1657 of 5484 Old 07-21-2011, 05:31 AM
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Originally Posted by Heath View Post
You replace a cam so the new gear on the OPDA won't start a odd wear pattern, but you leave the old lifters in the motor, not caring if they start a odd/bad wear pattern on the new cam? Did I assess that correctly? Does that make sense? Why do any of it?
Why get up in the morning? Why eat bacon?

My lifters and respective cam lobes did not have any unusual wear patterns, so for me there was no cause for concern. Everyone has bought into the old line of thought that a cam and lifters have to be replaced as a set or the world will come to an end. There's a lot of reasons why new (and old) parts fail, and sometimes people assign the incorrect root cause to the failure. I can tell you that in the world of warranty service, it's somewhat commonplace for dealers to replace either the cam or lifters independent of each other without any fire and brimstone raining down from the heavens as a result.

Living here in SE Michigan, I have access to a lot of people who not only disassemble and evaluate engines for a living, but people who design and engineer them as well. I spoke to several people about my issue and specifically even asked about the whole cam/lifter mating issue and they all dismissed it as an old wives tale, some even laughing about the hysteria surrounding the "issue".

You're welcome to believe what you want. My decision made sense because I did the research, interviewed the relevant experts and did an obsessive level of preparation to ensure that it would be a success.

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post #1658 of 5484 Old 07-21-2011, 09:36 AM
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Quote:
Originally Posted by TJJP77

Why get up in the morning? Why eat bacon?

My lifters and respective cam lobes did not have any unusual wear patterns, so for me there was no cause for concern. Everyone has bought into the old line of thought that a cam and lifters have to be replaced as a set or the world will come to an end. There's a lot of reasons why new (and old) parts fail, and sometimes people assign the incorrect root cause to the failure. I can tell you that in the world of warranty service, it's somewhat commonplace for dealers to replace either the cam or lifters independent of each other without any fire and brimstone raining down from the heavens as a result.

Living here in SE Michigan, I have access to a lot of people who not only disassemble and evaluate engines for a living, but people who design and engineer them as well. I spoke to several people about my issue and specifically even asked about the whole cam/lifter mating issue and they all dismissed it as an old wives tale, some even laughing about the hysteria surrounding the "issue".

You're welcome to believe what you want. My decision made sense because I did the research, interviewed the relevant experts and did an obsessive level of preparation to ensure that it would be a success.
I'm not going to jumble this thread up any more, I'll just add that, your lifters did have a pattern that you couldn't see with the naked eye. And I promise it will shorten the lifespan of your cam and lifters at this point. It has been well proven to be a fact.

As or being common to change cams without changing lifters, yeah people do it all the time. With roller lifters.

Also, how were you able to inspect your lifters for a wear pattern if they were still in the motor? How have you been able to inspect them and the cam now? Thats all I have to say about it.

Thanks

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post #1659 of 5484 Old 07-21-2011, 09:53 AM
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It has been well proven to be a fact.
Well proven by who? I've heard so many old wives' tales that everybody "knew" was true that ended up not true that I'm skeptical whenever someone claims something has been "proven". Remember, a scientific study needs both an experimental group and a control group -- i.e., a group that changed their lifters, and a group that didn't change their lifters. It also needs a sample size bigger than 1 -- a sample size of 1 has a 100% confidence interval (i.e., 0% predictive value). Where are the numbers?

I *know* that auto manufacturers have those numbers, because those numbers are important for deciding whether to replace cams and lifters as matched sets or not, which in turn is important for deciding what the least expensive way of satisfying warranty claims will be. But I don't have those numbers. Do you have those numbers? What are they? The O.P. says he consulted people who *did* have those numbers, and they laughed at the notion that cams and lifters had to be changed as a matched set. You say different. So what's your source?
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post #1660 of 5484 Old 07-21-2011, 10:07 AM
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Blah, blah, blah, I'm right!
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Blah, blah, blah, I'm right!
Take it somewhere else, fellas. I happen to agree with one of you, but your argument doesn't belong in this thread. Why don't you both be grown-ups and delete these posts that have sullied this important thread, please? As soon as you do, then I can delete this post (sigh)


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post #1661 of 5484 Old 07-21-2011, 10:12 AM
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Thing is, this would be an important data point to have when making a decision about whether to change lifters with cam. I don't have the data. One person claimed to have data. Another person claimed to have consulted with people who did have actual data. What is the data? If the first person could tell us what the data actually is (i.e., actual numbers) and who gathered it, that would be useful for making that decision.
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post #1662 of 5484 Old 07-21-2011, 10:24 AM Thread Starter
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At this point, I don't see the reason to change the cam. The FogMod will help with the binding issue, however there is still no definitive answer to the cause(s) behind the lower bushing scoring and potential shaft hardening issues.

Changing the camshaft (with or without lifters) will not necessarily result in good wear patterns with the current OPDA even if FogModded. The work TJJP77 is doing is only relevant to how two new gear patterns will form with the correct break-in, quality oil, and FogModded unit.

The debate of how to change a camshaft should be another topic covered in another thread.


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post #1663 of 5484 Old 07-21-2011, 10:38 AM
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Talking about scoring, the differential equivalent would be early pinion bearing failure. Typically that's a gear setup problem where the pinion is under excessive side thrust, generally because the depth of the pinion is wrong and is contacting the ring gear under excessive pressure. Given that someone reported that additional hardening of the shaft plus enormous increase in oil supply (oil supply which did not exhibit coking typical of high temperatures otherwise things would have been gummed up there and he would have noticed) did not eliminate scoring at the lower bushing, that's an interesting data point too.

The question for the lower bushing is what's putting excessive side thrust on the shaft that would cause it to score like that. I don't *think* that the mesh between cam gear and OPDA gear could put side thrust on the shaft like that... but...

The other question is whether something other than a steel bushing down there would be more appropriate. Someone's putting a brass bushing down there to see whether that helps. My feeling there is that a brass bushing will get wallowed out into an oval if the theory of excessive side thrust is true. It'll be interesting to see what happens there.
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post #1664 of 5484 Old 07-21-2011, 11:20 AM Thread Starter
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Given that someone reported that additional hardening of the shaft plus enormous increase in oil supply (oil supply which did not exhibit coking typical of high temperatures otherwise things would have been gummed up there and he would have noticed) did not eliminate scoring at the lower bushing, that's an interesting data point too.

The question for the lower bushing is what's putting excessive side thrust on the shaft that would cause it to score like that. I don't *think* that the mesh between cam gear and OPDA gear could put side thrust on the shaft like that... but...

The other question is whether something other than a steel bushing down there would be more appropriate. Someone's putting a brass bushing down there to see whether that helps. My feeling there is that a brass bushing will get wallowed out into an oval if the theory of excessive side thrust is true. It'll be interesting to see what happens there.
I don't think tkki has results from a hardened shaft yet. I agree about a bronze lower bushing wearing. It's the same reason I wouldn't put in a bronze gear. They are too weak.

Could the wear/pressure have something to do with the oil pump? We've seen consistent wear on the slotted tip of the OPDA shaft. Another thing, if the tip that sits in the oil pump is loose and the upper wheel has enough centrifugal force, could it create some wobbling of the shaft (ever so slight) that may create the wear? Lastly, what about how the OPDA mounts to the motor? I little offset could create some added thrust on the camgear and lower bushing.

Just thinking out loud.


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post #1665 of 5484 Old 07-21-2011, 12:03 PM
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Being that July is almost over, I wonder if we will ever hear from our good friends at Chrysler? I seriously doubt it.

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