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.