Quote:
Originally Posted by Scnell Gelb
I have read this sorry IMS tale several times by different authors/cars/different Forums. The cause cited is always that the Pelican Parts Instructions are both incorrect and damaging. These experts all agree these instructions are wrong and may cause expensive damage to your engine.That seems like an issue that the hosts of this Forum could easily correct.
I have read many kind helpful posts by JFP who is clearly exasperated by the Pelican Parts Instruction problem. He is one of the top M96 engine guys around. Yet Pelican ignores his advice. Why? It makes no sense at all.
I am not knocking Pelican, I have lots of their parts on my car,have Wayne's book but I am always leery of following any of their Instructions - not because they made one mistake(I make plenty more!) - but that this error has been up there for a very long time uncorrected.
Worse, Pelican also sell the LN IMS with the correct Instructions- so they must know?
What are we missing?
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Believe it or not, I think I can answer your question: Back when there was only an IMS problem and no solution, just about everyone was looking for a fix. After considerable experimentation, Jake and Charles developed the now familiar procedure that uses special tools to hold everything while replacing a bearing that even Porsche said cannot be changed with the engine assembled, now a very successful and widely accepted product market by LN and used all over the world without issue.
Pelican attempted to develop and introduce a low cost alternative, using a less expensive OEM style sealed single row bearing and a procedure that did not use the special tooling, but based upon holding the IMS shaft with set screws. While this methodology can actually work under certain circumstances, it completely lacks the "bullet proof" nature of the LN system, and can lead to all sorts of unintended outcomes. People drop the set screws inside the engines, they over tighten them and end up moving the chain gear on the IMS shaft, we have even seen engine cases stripped or cracked from the set screws. Unfortunately, the most common failure is for the cam allocation to jump on three chain engines.
This is not to say that there have not been "human engineering" issues with the LN procedure's; it is not for lack of a good reasons that both LN and Jake have totally moved away from technical support for this procedure. As with any complicated process, there is one way to do it right, and many ways to totally screw it up, and lots of people have done exactly that, usually by trying short cuts or trying to cheap out on the process.
I recently responded to a post on another site where an individual with a OEM IMS had the center bolt on the IMS snap off and fall to the bottom of the bell housing. He was annoyed because he could not get the IMS cover flange off after removing the bolts and could not understand why. After he posted photos of the problem, I noticed that one of the chain tensioners was still in place, and ask if he had locked the engine at TDC, locked down the cams, and removed the tensioners prior to trying to remove the flange cover; his answer was no, he was going to do that when he got around to ordering the tools. While he still had a broken center bolt to deal with, he never once realized he was one move away from a complete disaster, the chain tensioners were exerting enough load to prevent removal of the flange cover, which if he had gotten it off would have resulted in the IMS shaft jumping to one side and the cam timing jumping as the chain loads released. He would then have had a bad IMS in an engine that was not at TDC with cam timing problems and could not be rotated without doing even more damage.
Yes, I am a vocal critic of the Pelican procedures because of the number of otherwise good engines that were either endangered or worse by using it, and the people who attempted to use it. The procedure is a really bad idea, which unfortunately can actually work, but at very high risk. But by far, the biggest problem in IMS refits that go bad is the actions of the people that try to do them. To be completely fair, I have seen these go bad even at the hands of professionals, including dealer techs using the LN tooling and procedure's. There are many ways to do this wrong, and only one way to do it correctly. To anyone that asks, I suggest getting the latest version of the LN procedure's online (a PDF file), read it, re read it, and then read it again; so that you understand what is involved. If you do not understand these instructions, or do not want to purchase the tooling, don't do the retrofit yourself; take it to someone that does understand it and has the tools.
Jake once commented that he has greater confidence with someone doing a retrofit for the first time than someone who has done several. and has become more casual about it. That is a very wise observation, as the first timer is going to basically be scared ****less and take his (or her) time to check and double check each step, making sure that they understand the method and have everything they need before starting. That combination of fear and caution typically leads to a successful refit. You cannot be careless with a $15K engine that your next move can reduce to being a boat anchor.
As for the set screw procedure, the world would be a better place without it; but unfortunately that boat has already sailed. If asked, I would tell people to ignore it and follow the LN procedures, but then this becomes the moment that the "human engineering" factors step in................