Your chain is not on the intermediate staft sproket completely or is completely off from it. I had the exact same symptoms you have (but it was still on the engine stand) engine would turn one way, almost all the way around and ckink stop. Its REALLY hard to see if the chain is indeed on both sprokets. I cannot imagine how it could be put back on in the car. ON an engine stand you can put the disconnedted cam up and the chain will hang. You can then try to manover the chain down and sideways to get it back onto the sproket.

NO chain will stretch this much without breaking. IF the tensioners this far in the chain MUST be off the sproket, WHAT else coud it be?

read the entire thread jack, we're way past that.

you will have to retime the cams, so put that thought out of your mind. and you can't feed in the chains without turning the crank. re-read my previous post.

Not sure if the problems has been 100% indentified (not familiar enough with 911 specific engines to be sure) but there may be two factors at play:
1) machined case/heads which reduces "deck height"
2) worn-out chains due to mechanical tensioners

#1 may have been done to increase the compression ratio (i.e. heads machined) and/or true the case. This will reduce the distance between the cams and crank, create a slack chain, and retard timing.

#2 may exist because of the existance of mechanical tensions. These are a Bad Idea because they can not deal with the motion of the chain and cause excessive loads in the system. These loads cause excessive wear, and lead to a "stretched" chain. I say "stretched" because the metal does not actually stretch, but the pins become smaller, and the holes in the links become larger. Typically 0.5% elongation is the max, mainly because of tensioner travel and cam timing.

Seeing as how the timing was already retarded 6 degrees, I would say it was more an indication of an elongated chain or insufficient cam/crank distance. Chances are the heads/case weren't machined excessively, and the chain could be replaced with a brand-new one. Mechanical tensions will just wear out a new chain in short order, even if the tensioner itselfs appears to last forever...

Best of luck.

Matt Beaubien
'73 911E

John:

Thanks -- sorry I didn't understand your previous post about not being able to feed the chains without turning the crank. I'll start amassing the stuff to do this

Now this may be a bit incredibly silly, but I did find this "link" from an alternative vendor which is supposed to be for the 911 timing chain. Is it possible to just remove a link and insert this new "master link" to make my existing chain the equivalent of a "master link" chain.

http://forums.pelicanparts.com/uploa...Chain Link.jpg



Snowman: I thought that was the problem initially, but Keith and I both checked and it is on the sprocket. I have put 25 miles on the car back and forth to the shop.

Mr. Beau: If 0.5 percent is the maximum stretch these things can achieve it seems really weird that it would have this much slack. Anyhow, it is probably a combination of both factors.

Rich

What sense would there be in just putting a ML in your old chain?

If no machining has taken place to shorten the cam/crank centerline, then the chain is too long. In your case, it's probably more than 1%. 1% may not sound like a lot, but when it comes to chain wear, it is, and could have easily been caused by solid tensioners (which is why you constantly adjust them--to take up the wear you're imparting in the chain).

A possible Poor Man's Solution would be to put in a half-link in place of a full link which would shorten the chain considerably. Normally this would be done if it was machining that created the slack, and not chain wear. If it is really chain wear, you are in some danger of having the chain break. This is pertty un-common, though possible. Depends on how much you plan on driving it, and how much time/money you want to put into it...

Matt.

I read all the posts and I do not think you are REALLY beyond the point I mentioned. I think you may need to recheck more carefully.

When things get to wierd, go back to the basics and re do them.

Rich,
Please read the entire thread again and create a check list of possible causes, then verify each has been dealt with.

The chain appears too long due to any number of reasons. Using a mechanical tensioner is not the long-term solution; getting the correct idler arm geometry is. If the mechanics of the rebuild are okay, then it's a matter of getting this area to look the way it did from the factory. The solutions are in this thread.

Let me repeat: Using a mechanical tensioner is not the long-term solution.

Sherwood Lee
http://members.rennlist.org/911pcars

I am going to replace the chain this week sometime. I need to get the parts (chains, gaskets, etc.) and the little jig to hold my dial indicator so that I can do the cam timing per J.Walker. I'll post the results of the chain replacement and see if it cures the problem. I am tempted to get new sprockets while I am in there as well.

Rich

Rich,

Step back, save your money, hit yourself in the head a few times with a monkey wrench and ask yourself, What am I missing? Throwing money at new parts, ie sprokets, is not a solution to a problem like this, its an outlet for flustration. Drink a couple of beers, take a deep breath, and say to yourself, lets look at this again, from scratch.

Did chain replacement solve the problem?
 

Hi Rich,

Sorry to revive an old thread but...

I was reading your thread on the 2.7 timing chain issue and noticed there wasn't an update when you replaced the chains. I have a similar situation with a 2.7 that had mechanical tensioners. After installing the oil fed tensioners, the left side inler arm extends to the cam housing. Thus, the chain rubs at the base of the idler arm when cold. Once the engine starts to warm it stops rubbing.

This brings up a question for the experts. In my case the engine expands significantly enough when warm, to pick up the slack in the chain, so it does not rub on the idler arm. Therefore, if the mechanical tensioner were adjusted too tight when the engine was cold, then when the engine warms the chains, cam bearings, idler arm shaft, would experience a significant load, side load etc. What type of periferal damage could have occured?

Back to Rich. Similarly, I do not know the history of my motor. Although, I can assume it had a top end rebuild because the PO attemtped to seal rocker arm shafts with high temp silicone instead of o-rings. Did the chain replacement fix the problem? Did you replace the ramps and sprockets?

Thanks for your assistance.

Jason 74 911

Jason (and others):

Sorry for not updating the board on this project lately. I ended up putting in the Porsche master link timing chains and pulling the Carrera pressure-fed tensioners from my spare 2.4 liter. Don't worry about re-timing the camshafts -- it's a piece of cake! Anyhow, I installed them about 2000 miles ago and the car has been running just fine. I have been driving it pretty hard and there has been no problem with the master link chains (I figured if Porsche supplies them they must be OK). The 2.7 liter really pulls hard in the midrange with the webers and with the light early car, it really moves. I am very happy with it.

For all of those who worry about used engines that have sat for a long time, I can say I have had very good luck with them. I bought a complete 2.0 liter out of garage where it had been sitting for six years for $800, cleaned it up, stuck it in and drove it for almost three years. As part of the mega-package, I got an old 2.2 liter engine that sat for many years. KeithO64 and I cleaned up and stuck in the chassis and it has been running strongly for many thousand miles. It runs very strong and clean up to 7000 RPM every time. I sold one other used 2.7 liter engine that I got in the package and that worked out OK as it is running somewhere up in Oregon. Once the problems were sorted out, my 2.7 is running just fine. All of these engines sat for many years, but worked just fine once they were cleaned up. If I was going to run LeMans, I would do things differently.

Anyhow, it runs fine. I have been absent for a while since I acquired a nice used 325i for a track mobile. Hopefully it is back to the Nurburgring next August!

Rich

Jason,

By mechanical tensioners, do you mean the type with a "set screw" that you adjust to obtain tension? If so, the are a Bad Idea as they will cause mega chain wear. As you noticed, things expand when hot, and the tension varies considerably with a "fixed" tensioner and causes all sorts of problems. While they may be more reliable than the factory types, the make all sorts of other parts unreliable...

Hi Matt,

Yes, I do mean the mechanical tensioners with a set screw and lock nut. I don't recall the amount of tension on the chain when the mechanical tensioners were installed but I am assuming it was tight due the amount of chain slack I have now with the carrera tensioners, on the left side when cold.

The motor runs strong so I am planning to replace the chains and ramps. However, I would like to know what type of damage could have resulted from tight timing chains and what to look for.

Thanks for your reply,

Jason