Wayne, John Walker -- Help! It turns counter clockwise, but not clockwise..
 

Dear guys, I hope you can help me with this --

It is 2:15 AM here in San Diego and I was just putting the finishing touches on my new 2.7 -- literally just installing the distributor. When I went to turn it over to the #1 firing position, it wouldn't turn -- like something was in the cylinder. Well that got the placque moving, as I pondered pulling the motor and tearing it apart. I turned the engine in the reverse direction 360 degrees thinking that I could at least isolate the cylinder where the foreign object might be (and maybe get it out) it turned beyond 360, beyond 720 (this is weird) but then when I tried to go forward, it was like it was locked again but in another position. I backed it up again, and the sticking point moved again. I back it up and it turns fine, but then try to go forward and it sticks. But it keeps sticking at different points.

I could swear I heard a metallic clicking sound in the right side chain cover as I backed the engine up a couple of the times.

The engine seems to turn in reverse just fine, it just won't go in the proper direction.

I had the engine on the stand for a long time and it turned over and over just fine. I changed and installed the pressure fed tensioners (it had the solid ones before per my earlier post about identifying the solid tensioners). Then went in easily and the cams didn't move a micron in the process. I then put the engine in the car and I had not really tried to turn it over until just trying to line it up for the distributor.

PLEASE TELL ME THAT IT JUMPED A TOOTH ON THE CAM SPROCKET AND I ONLY HAVE TO RETIME THE CAMS AND NOT PULL THE ENGINE!

Thanks much in advance for any assistance and suggestions to confirm the diagnosis.

Rich

Hmm, this is not good. If you jumped a tooth on the cam sprocket, then the valves might touch the pistons, but it would be the same forwards and reverse. Sounds like a timing chain problem of some type. In fact, it almost has to be. There isn't anything in the bottom end that would cause forwards movement but not backwards movement.

Check the distributor. I can't imagine it holding anything up, but if the points were loose, it might happen.

Pull off the chain covers and look. I think that you will probably find the problem right away as you turn it forwards and backwards.

-Wayne

The timing chain on the right side is binding. You will probably need to pull the cover on that side and it will be clear what is happening.
Good luck, and post your findings -

I have thought about it and believe you are right. My mind was not totally functional last night I don't think. I think something must be wrong on this side of the engine. I will pull the timing cover and post what I find. Hopefully, it will just mean retiming this cam.

Thanks guys,

Rich

Rich

Is it possible something is binding the chain after you upgraded the tensioners? Since it turned over in both directions prior to the tensioner change I would pull the covers and check it out. Does it turn over without the distributor installed? Do you have the plugs in? I will call you in a while.

That is what it is. Happened to me too.

Yelcab1:

Thanks for the reassurance. I was getting a bit panicky thinking I needed to pull the engine again. I will take off the cam cover tonight and see what is in there and post (unless it is something incredibly stupid like I left a socket wrench in there!)

Rich

it's probably the tensioner collapsing, and allowing the chain to go slack, due to no oil in it, the snapping noise anyway. did you pump it up in a can of oil, or just pop it in dry? you could recheck the cam timing by setting up the gauge on #4 intake. as for binding, that's kind of odd, but possibly the slack chain is bunching at the intermediate shaft sprocket.

It sounds like we have a consensus that the problem is in the cam timing. The tensioner had oil in it from the other engine that I pulled it from but I did not reprime it before installing it. I'll post pics of what I find. Thanks John.

Rich

I doubt it's the cam timing, as this would cause problems going in reverse too. Sounds like something with the chain. Pull the covers, and let us know what you find (pull both left and right).

-Wayne

I just didn't have the stamina to do it last night, but I will pull them tonight and take pictures and post tomorrow or late tonight.

Rich

I figured it out
 

It turns out that apparently the chain has stretched sufficiently that it is hitting the cam housing itself. Take a look at this picture. The reason it won't turn is that the sprocket is contacting the aluminum case (right circle). There is so much slop in the chain that there is actually air between the top of the tensioner and the point of contact with the armature and the chain is almost touching the upper guide. This would have been a huge mess if it started like this. I guess I am glad I found it now.


http://forums.pelicanparts.com/uploads/problem 3.jpg

The question is, can I replace the chains without dissassembling the engine?

Thanks again for your help with this.

Rich

Wow Rich! After seeing Chris Streit's engine getting assembled, I'd GUESS you'll have to open the engine up to replace the chains :(

Sorry dude. Like you said, good thing you didn't start it!

Hi there. No, you don't have to open up the engine. I'll tell you in a sec. However, this is an excellent example of why you should replace components like chain ramps, chains, and other things that happen to wear, when you rebuild your engine.

I must admit though, this seems like extremely excessive play. There might be something else wrong here. I can't imagine the engine running properly (assuming that it ran okay when you tore it apart) with the chain this loose.

As for chain replacement (assuming that's the problem), you can install what is known as a master link chain (we sell them). This is a factory part (they have a Porsche part number for it). It allows you to break the chain and snap it together, after you put it around the intermediate shaft gear.

I would hazard to say that your chain may have come off of the intermediate shaft - especially if there isn't an equal amount of slack on the other side...

-Wayne

Agree w/ Wayne, chains do eventually wear out, (though not quickly, some last 100s of thousands of miles), but they cannot stretch much. How many miles on the engine (chain)? I would check everything else first. :cool:

Wayne, how many cases of master link usage do you know of? How long did they last? I am scare of master links for my motorcycle chain use, and if the ML used for our motors have a tendency to break as ML on motorcycle chains do, I'd not go that route. (Just being my usual contrary self :) )

But Wayne and Dennis may be right on about the chain having come off the immed-shaft gear.

For my 2 cents, the chain is not on the intermediate sprocket properly. The position of the tensioner tip on the arm is way off.
It can't possibly run that way so something happened during the service.
The chains don't actually stretch....the combined minute wear in each of the links and on the sprocket, gears lends itself to a little more slack.
If you choose to replace chains...please, please don't remove the old ones before connecting to the new ones to pull them through. Don't ask me how I know this will cause a major problem!

The chain is not stretched that much. It is simply not on the intermediate shaft sprockets correctly. Been there and done that!
You will have to remove the chain sprockets from the cam, loosen all the rockers so you can rotate the engine without hitting a valve and get the chain set right. It can be done, since the exact same thing happened to me on my last rebuild only I noticed the problem when installing the cams, etc. See the picture below.
I have a brand new chain with master link that I will give you if it turns out you need it.

http://forums.pelicanparts.com/uploa...imingchain.jpg

Here are my thoughts/comments;

First, check to make sure the chain is on all of the gears. Is it possible that it slipped off the intermediate sprocket as Wayne alluded to? I am speaking in generalities since I have not touched a chain install.

Second, if the chain is on all the gears, would it be worthwhile to reinstall the factory tensioners back on? Could the new tensioners be a little different in size? Could the heads have been milled and the other chain tensioners modified to get the correct tension? Again, I do not know enough about the chain but this is food for thought.

Third, if both of these are not the case, order a chain from Wayne with the master link setup and we can do the job while I am out there.

Do you know if the middle cover can be removed without while the engine is in the car? I think it can but am not sure.

My gut is that the chain slipped off a sprocket somewhere, I can not see a chain stretching that much. Either way, if you want to mess with this while I am out there you and I can do the job when everyone is sleeping. I do not think it will be that difficult for us to do.

Also, I just saw the post from Thomas. Thanks for posting that, I wondering if that is what happened.

I am a user of the masterlink chain, on my motorcycle and the Porsche. Neither has broken yet.

Souk, I thought the same thing and wouldn't use one on the Duc regardless, however I know a number of people that have used them forever in the 911 motor with no problems...

I never had a ML problem in my MC days and further, the 911 engine timing chain environment is WAY different from the final drive chain on a MC. MC final drive chains do not last 20 years and 200k miles. To say the least.

Just a random thought......
Masterlinks on m/c chains have fallen by the wayside somewhat, with the advent of o-ring sealed chains. The last one I installed (Regina brand), was of the endless variety, using riveted pins, no link. As one would imagine, they are not as easy to install.

One thing about master link chains, I know this applies to motorcycles and makes sense in the timing chain application as well. Make sure when you install the master link, its closed end is the facing the direction of rotation. So, if the chain rotates clockwise, the ML's closed end would pass the 6 o-clock position prior to its open end. The reason for this is if the chain/master link happens to hit the side of the case while the engine is running, it wont get pushed/knocked off its pin causing the chain to come apart.

Thanks for all the suggestions and I will definitely try to see what is going on soon. It sounds like we have agreement that it is not on the intermediate shaft correctly and I will get my flashlight in there and see what the story is. It is very weird that it just decided to do this -- it turned over fine many, many times on the engine stand with the solid tensioners and I maintained constant pressure on the chain while swapping in the pressure fed tensioners. I have to go out of town for a couple of days starting today, so it will be until next week when I find out for sure but I will post again with the findings. I'll try to take a picture if I can get my camera in there somehow

Tom: Thanks very much for the generous offer on the chain. I will let you know if I need it. Thanks.

I wish I knew more about this engine. I bought it along with a bunch of stuff and from all appearances it was rebuilt with no miles on it. All of the ports still have the machinist's blue from the valve job and the ports surfaces are clean as a whistle. It looks like it might just be a top end rebuild, but when I took off the inspection plate and shined a flashlight up inside it looked awfully clean and nice. Anyhow, it came as part of a package deal that included three engines, a chassis, etc, etc, etc. for a great price. Everything has been really good so far (One Pelican member bought the other 2.7 liter and it is in his 914 and running well and KeithO64 has the other 2.2 motor and it is running fine in his car) so I did not rebuild it myself, but I kind of wish I had. If I had done it myself I would have been confident in all of the pieces that went into it. I am putting this in and crossing my fingers. I will start soon on my 2.4 and 2.0 liter engines (by the way Wayne, the new book is great and so is the CD! Many kudos for doing something for all of us.)

I am glad to hear that I can replace the chain (if need be) without disassembling the engine. Master link chains are not ideal, but if it is a factory Porsche part, I imagine that it should work pretty well. This is not a high RPM motor that is going to see a lot of track use and it will driven but probably not more than 10000 miles per year -- it will last for a couple of years anyhow.

Keith: I think I know what you and I will be doing next Thursday night. The beer is in the fridge!

Thanks everyone for the help and advice and I will keep you posted.

Rich

keitho64 - EXCELLENT POINT! I had completely forgotten about that. Since we now know the 'history' a bit on this motor, let me suggest something else.

It is possible that the rebuilder went ballistic on this engine and didn't know what they were doing (why wasn't the engine ever installed?) If they had my book, they would have known what to do and what not to do <- subtle plug.

Anyways, perhaps the machinist/builder tried to increase the compression ratio a bit too much, or machined the case incorrectly. Taking too much material off of the heads, or machining the spigots of the case will move the cam towers closer to the case and make the chain loose. The solution is to remove a link and use a special sprocket (photo of this in Bruce Anderson's book) that is a bit smaller.

I wonder if this is the problem. Now, I'm curious, and I don't want to wait three days to find out, rats!

-Wayne

I wonder if this is the problem. Now, I'm curious, and I don't want to wait three days to find out, rats!

Wayne - I am sure Rich would welcome you coming to his house to resolve this while he is on vacation. :D Besides, I will be on the left coast next week and I would get to meet you.

Anyway, I think I will be involved in this soon since Rich is being kind enough to let my family stay at his house and trash the place. We will put our heads together (I know bad Pun) and see what is going on.

Any suggestions as to how to tell if the heads have been milled without removing them? Is it possible the original tensioners were modified if this is what is going on? I just love solving mysteries.

Wayne:

I'll leave the key under the mat if you want to come down and look at it or you are welcome to join Keith and I next weekend (late night) to check this out. I want to go home and look at the intermediate shaft but darn work is getting in the way again.

How would I check to see if the heads were milled?

I have an idea for a product for Pelican -- an inexpensive flexible fiberoptic borescope for looking into the engine or transmission. I have been on the verge of asking doctor friends if they have an old one somewhere. It would be so great because you could just insert it into any little hole in the engine and transmission (they have little headlights on them) and snake it around and see with your own eyes (or on a video monitor) just what is in there without taking it apart. This place has an interesting product for about $250: http://www.tooldesk.com/shop/borescope1.wml

Again, thanks for the help.

Do you mean this borescope, which we sell in our TOOLS section:

http://www.pelicanparts.com/catalog/shopcart/DWKS/POR_DWKS_toolsG_main.htm

I have seen both of these, and they work great!

??!!??!!

Okay, how can I get people to find stuff in our catalog easier? This is a huge problem!

-Wayne

Rich - Wayne is tempting you with the order. Will you have one of these before I get there?

Slipping on a new chain with ML (as long as the closed end of the ML points in the direction of travel) is o.k. but........After so many miles, the chain sprockets on the intermediate shaft have worn along with the chain. The new chain will have the same pitch, but no wear, therefore exacting a different force on the teeth of the sprockets, especially since the I. S. sprockets are the drivers. In industrial high speed applications, we prefer to use new sprockets with new chains for that reason. Some of you who have used new chains, but not new sprockets, may find the tips of sprocket teeth on the bottom of your sump. Have any of you had this experience? Wayne or J.W., have you seen this happen? :(

I REALLY hate to say this, but the best way would be to put out a paper catalog. People spend a lot of time browsing physical catalogs and they use computer based catalogs to find specific items, not to simply go from page to page looking at the stuff. Therefore if they don't automatically associate Pelican with tools (in this case, the association is with parts) browsing the Pelican is how the association would be made.

The other way is the BBS. You just let a bunch of us (like me) know that the tools section has even more than I thought. Now I have a better idea of when to go to Pelican for specific tool searches.

My .02 from the :30 commericial and advert. world...

What you need is a search button for catalog as convenient and easy as the quick reply box is on these pages. If you had such a thing, we could type it in right here and look.

Those are good suggestions. I did add the search field to the top of this forum, and I also fixed that search bug. It had been on my list to fix for quite a while, but you know how these things get pushed aside when there are cooler things to work on (like the Engine Rebuild Wizard)...

-Wayne

Rich,
I guess I jumped into this a little late, but here are my observations.

How does one tell how much material has been removed by machining (heads, crankcase, cylinders, etc.)? All of these can be machined as part of the prep for assembly. There could also have been previous attempts to increase compression ratio by flycutting the head gasket surface and trimming the cylinder heights as well. All of these machining operations, as Wayne points out, positions the cylinder head/cam housing closer to the center line of the engine resulting in increased chain slack.

When this happens, the camshaft is no longer centered in the stock chain box opening. This will make it difficult to install the O-ring assembly. If somehow installed despite this misalignment, it may eventually create an oil leak path. To compensate for the repositioned cam location, the chain box-to-crankcase mounting surface should be machined an identical amount that was machined from the aforementioned cylinder heads, cylinders, etc. Now what?

Now you have a chain that has more slack than a stock engine. As Wayne also mentions, you can install a custom cam idler sprocket to bring the idler arm back into the correct operating position. However, the sprocket must have a larger diameter than stock (as opposed to a smaller sprocket wheel).

Let's assume the chains (new) and sprockets are in full engagement, the chain boxes are properly machined, oversize idler sprockets are installed and the chain is still too long. Others may weigh in here with different opinions, but I'd try removing a link from the chain, then reassemble (probably with the stock idler sprocket). As long as the proper valve train geometry is maintained, albeit with one less link, this should work. Let me add a caveat in that it's entirely possibe I'm overlooking something.

As to the question of knowing how much material was removed from the cylinders/cylinder heads and crankcase spigots via machining - you can measure the thickness of the chain box wall where it bolts onto the crankcase. If the cam is centered in the opening after all the previous machining, then the chain box mounting surface has been machined a like amount. Compare the thickness of the chain box "wall" with that of a stock, unmachined chain box. B.A. recommends no more than 0.040" be removed from the cylinder/cylinder head "stack". You may find your measurement is more than this coupled with a well-worn chain.

BTW, in case you already found the easy fix, disregard the above.

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

Well, I just thought I would update this thread, THANK ALL OF YOU GUYS VERY MUCH FOR YOUR SUPPORT AND IDEAS and let you know that IT IS ALIVE!

KeithO64 was visiting this weekend and we spent Tuesday night looking at the problem. We looked and looked and turned and inspected and checked and watched and turned and just came to the conclusion that there was no way in the world that the chain was off the intermediate shaft sprocket. We also noted that the intermediate shaft gear was brand new, so somebody had taken some effort to rebuild this “mystery” engine. So, we looked in Wayne’s book and compared the pictures and noted that the earlier cars did not have this little lip (see yellow box in picture below) that the sprocket was hitting. Then we noticed that the chain boxes had a 930.xxx part number. We checked the other two engines I have and just like the book, there was no lip like this in the chain boxes. Since I have no idea what function this could serve (maybe strengthening for the air conditioning mounting???) and was clearly not necessary, we did what any good hot rodders would do and got rid of it.

http://forums.pelicanparts.com/uploads/sprocket.jpg


We plugged all the passages with paper towels and Keith ground off the vertical part with a sanding roll on a line all the way to the front of the chain box. He removed material on a line about where the yellow vertical box line is in this picture. A shop vac and lots of Gumout to clean things out and it looked pretty good and there was no clearance problem anymore. We buttoned up the rest of the things on the car and the next day (the neighbors would not have appreciated a car with open exhaust at 3:00AM) and on the second turn of the key, the engine popped right over and ran great with no leaks. Keith set the timing at Z1 and it idled fine and the exhaust is clear! We toasted our success with a couple of German beers but unfortunately Keith and his family had to leave. It is just going to need some fine tuning (wife’s book club tonight) and it should be on the road soon. What a relief.

I have no idea why this was a problem on this engine. On close inspection, the chains appeared new. Maybe the heads have been milled or something that caused this problem, I have no idea. However, I just wanted to let everyone who contributed their thoughts to this project or who might run into this rather weird problem that there is a potential solution and it seems to work fine. I will need to get it running, give some driving impressions and perhaps get some G-Tech data for discussion.

Thanks to everyone again for their help, especially Keith for taking time out of his vacation to work on this.

Rich

i thought that the tensioners were extended as far as they could extend, and there was still chain slop. what about that? that shelf has never caused a problem for me.

Yes, I don't agree with your analysis. I'm with JW on this one. I've never heard of these clearances being a problem. I would not drive the car until you figure this out, as this can destroy your entire engine. The angle of the chain tensioner with the sprocket holder looks too severe...

-Wayne

Have a master chain setup on my twincam Lotus, haven't broke, but that hasn't stop me from tagging a few valves. Unlike the newer engines, or an old porsche engine, the chain tensioner on a Lotus twincam must be adjusted every 3,000 mile manually, no hydraulic tensioer or self adjusting spring tension, just a screw and a lock nut.

Lotus must have brought the chain from a english bicycle manufacturer, it only A SINGLE ROW CHAIN, NOT A DOUBLE.

Even though I rebuilt both of my Lotus engines more time than I care to remember, I never did a complete tear down on a 911.

I was just wondering if the chain for the left cam is the same as for the right cam? Since the tensioners are not the same is there also a difference in the length of the chains?

Just thinking, but I try not to do that too much.