what do u guys think of my tech arcticle

[pjv911]

Changing the chains without spliting the case is not a easy thing to do but its much easier than i thought it would be.
What had happened to mine (69` r/s clone with a 77` 2.7 )was that the previous owner of my motor had the chain guides in backwards and this caused the chains to flop around and caused the chains to stretch resulting in my right side tensioner wheel to rub the housing.
After pulling off the exhaust I found that it looked near impossible to get the new chains around the crank gears since the gears are nearly impossible to see even with a mirror.
After looking in every shop manual printed I could not find a procedure to change the chains without splitting the case. Although there was a few that said you could but just plainly said remove chains and reinstall new ones, and that did not help me figure out how to get them around the crank.
Here`s what i did
First thing is to remove the oil drain pan to have inside access to the left chain gear. Next was to remove the left side (driver) tensioner,wheels,cam gears,and guides. Oh yea make sure the engine is at TDC (Z1). Next step was to remove the chain by either grinding a random link or open the master link (if your chain was allready replaced).I had one of each since my left side chain had been changed allready.
After opening the chain I used the master link from the new chain and connected it to the old one.
Next step was to make a tool to slip in between the chain and the top side of the crank gear (I cut a piece of plastic 1" by 10" flat) My homemade tool looked like a ruler but was thinner and more flexable.
I worked the plastic tool between the top of the crank gear and the old chain.Once the tool is inserted far enough I pulled the chain from the old end and with ease I pulled the old chain out while pulling the new one in place. Next was to disconnect the link which held the new and old chain together and connect the chain as intended making sure the center link of the double roller was in place and that the locking clip had the closed side facing engine rotation. The chain did however slip off the tool and fall behind the gear but without much difficultly I was able to put the chain back on the gear by using the oil drain pan passage for access to the gear from the inside, making sure the chain was on both sets of teeth.
Next step was to put the left side together using new guides and putting in new hydralic tensioners(which is a whole different animal). The correct way the guides go is to have the long end of the guide facing the nearest gear. When installing the one`s that are in the case which use the through bolt make sure the little plastic clips lock in place or the guide will not be inline with the chain. Also remember that the right side inner lower guide is different from the rest but looks very similar. After putting it all together on the left side without the pin in the cam gear,I installed the tensioner wheel and tensioner by pushing up on the tensioner wheel letting the cam gear freewheel on the cam(no pin)while i took up the slack in the chain. I had the cam timing right in the ballpark since I never rotated the crank or the cam.
The right side was done the same way and I didn`t have to worry about the chain falling off the homemade plastic tool since the chain has no room to fall off in this side.
After setting the cam timing I was ready to button it up.
All this took about 7 hours but if I had this info I could have done it in 5 hours or less.
Also my camshafts dont have the dot which is supposed to face up at TDC which is noted in the cam timing procedure in most manuals. I found that the #911 stamped on the face is what is supposed to face up. I hope my experiance with this helps someone out.
Kurt Williams

[pjv911]

doesnt anyone have a opinion?

[Doug Zielke]

Shhhh!
I'm still reading it!

[machintek]

Thanks Kurt. I printed it for future reference. I believe that replacing the guides and such is inevitable for all of us.

George
83 911SC Cab/Euro

[Fishcop]

Good on you Kurt for going to the trouble of writing your discovery down. I say email it to Wayne, it is worthy of being placed in with the rest of the tech articles for every ones' use.

Cheers

------------------
John Forcier
69 911T

[Wayne 962]

Any pics?

-Wayne

[Roland Kunz]

Hello

Klann has a tool to cut and rivet chains.
Mostly used for Mercedes cars.

You just cut the chain and hang on the new one then turn the engine until you have the complete old chain out and use a lock or the press to make it endless.

It is realtivly fast but still lot of work.
Mostly the chains will work long enough to be replaced by a major overhaul.
I also suggest to change the gears with a new chain.

Grüsse

[pjv911]

sorry wayne no pics.

[pjv911]

Roland I feared simply turning the engine to pull the new chain since the pistons and valves would come in contact. Thats why I slipped it over the crank gear.

[safe]

This will probably be very helpful when I'm doing it in a few weeks.

But cant you do it like Rolad suggested? If you turn the crank real careful and try and rotate the cam along with it? My local Porsche dealer (official) suggested that.

Maybe you could cut the old chain between the cam sprocket (left side) and the crank. Hock up the new chain to the old and place the new chain over the cam so it rotates along with the crank. If there is room of course with the housing in place.
A friend of mine said he used to do that all the time (Saab 9000) when he was a Saab mechanic.

[rhaas]

what I did with my chains was to driil out the rivot in the old chains, I then hooked the new chains to the old chains and cranked them through. I loosened the valve adjustment screws on the cams and I could rotate all day without the pistons touching the cams. Saved me all kinds of work. From then on it was setting cam timing and adjust the valves.

[billwagnon]

whoa! time warp!

[Gunter]

I would never again use new chains on old chain sprockets: The pitch is the same but the sprockets are worn on the bottom of the tooth valley to a point were the new chain links do not completely sit in. Just think about it and add up the tiny difference between the worn tooth structure on the sprockets and the new links in the chain going around the sprockets. Personal experience:
Rebuild at 160k miles, new chains, ramps, etc. Runs great! After about 15k on a routine oil change with sump off, a lot of teeth are in the screen! Wow! On closer inspection, and counting, they are the tops of the chain sprocket-teeth. All of them! No other choice than to split the case, yep, both chain sprockets have all the tops of the teeth missing. The ALU gear was good, the ramps were still good, idler sprockets good, alignment checked out, no other wear.
I thought about it long and hard and it makes sense to an old Mech. Engineer. In high-speed industrial applications, we always replace both sprockets and chains because mating the new chain to a worn sprocket is not acceptable.
I can hear the replies: I never had any problems with fitting a new chain to old sprockets, o.k. good luck to you! But, have you ever checked the condition of the sprocket teeth after you have used a new chain on old sprockets? Run for about 10-15k and have a look. Sadly, the sump plate disappeared after '83? so, there is no more screen. For anyone who just feeds a new chain on to old sprockets: I would be very concerned about the teeth wearing to a point of jumping with disasterous results. In fact, I will take pictures of the worn sprockets with my new digital as a warning.
I just noticed Roland's reply: Quote: "I also suggest to change the gears with a new chain." Right on

[pjv911]

Gunter your point makes sense . For instance when you change the drive chain on a motorcycle you must always replace the sprockets as well or premature wear will result . In my situation the engine was freshly rebuilt and was assembled wrong (guides were backwards) . The result was chain stretch on the left side . I fully inspected all the gears and even compared the cam gears to new one`s that I had bought just in case($100.00 waste) I needed them. But dont get me wrong you do make a valid point that applies to a worn engine such as yours that had 160k . But then Roland allready said that.

Kurt Williams

[safe]

Gunter: I doesn't like it either, but not changing the chain is not an option for me and likewise splitting the case.
I will change the chains and cam sprockets then run some miles this summer and inspect the sump screen as you did.

/Magnus