Timing chain rail installation.....

[skrufy]

Hi everyone-

I did a fairly thorough search of the archives and didn't find exactly what I'm looking for-

I have a hundred parts scattered around on my garage floor- I was VERY lucky and caught- or heard, the timing chain start slapping the case on my '77 930...... I wasn't sure I heard it correctly in the garage, backed it out of the garage 15 feet, head near the right side- Yep!- the dreaded chain slap = chain tensioner on it's dying laps.... put it back in the garage, shut it down....

lots of time removing Turbo plumbing/Turbo/wastegate/muffler/side pipe up to the cross over pipe - removed all that as a unit- have since dissembled all that to clean stuff/paint..

drained the sump oil, removed the flexible oil line from the scavenge pump to the forward oil coolers- was leaking- got a new hose/crimped fittings, lowered the engine down about 5 inches (REMEMBER - IF YOU EVER DO THIS, YOU MUST OPEN THE REAR TUNNEL COVER INSIDE AND DISCONNECT THE SHIFT COUPLER BY REMOVING THE CONICAL PIN- OR YOU WILL BEND THE SHIFT RODS IN YOUR TRANSMISSION BIG TIME...)- (also this would be a good time to check the nylon bushings in the shift coupler- they fall apart with age- new coupler is $115, or new bushings are $20- easy fix...)- oh yea- don't forget to support the engine with a jackstand....

got all of the stuff out of the way- right chain cover came off- things looked ok- chain tight with a little bit of lift possible off the bottom rail- tensioner looked/felt tight- could not compress it w/ flat screwdriver.....humm! I heard the right side slapping I thought...

left cover off: culprit! the lower chain resting on the rail was loose- could lift it about an inch off the rail- not good Kimosabe.... with the Z1 mark correct and distributor on #1= #1 cylinder at TDC, the "930 dot" on each cam end weren't exactly together when I compared them from above: the left cam was maybe 2-3 degrees less towards vertical when compared to the right side..... both sides had the early tensioners installed w/ 915 (or 910?) part numbers- I was expecting the tensioners with the 930 part numbers- which would make them the 3rd generation style as mentioned by Wayne in his book.......

anyway, the right tensioner shaft was tight and extended about 3/4 inch beneath the idler arm and wheel... the Left tensioner was only extended about 1/4 inch beneath it's idler arm- meaning that this tensioner was taking it's dying gasps, the spring wasn't strong enough to exert the pressure on the idler wheel to pull the cam via the chain into it's proper position.......the left cam was behind the right by those 2-3 degrees- so with a trusty 17mm open end wrench, it was an easy turn of those few degrees on the cam to get it into the proper position, taking out all the slack that I found on the bottom of the chain...... the Left tensioner now was extended out like the right side.....- but mushy but not all the way gone- maybe in a few more minutes of running, or a couple of miles down the road- BAMM!

I have all my Carrera pressure fed tensioner parts in, with the proper spacers ready to go-

BUT my chain rails are 32 years old- so I was thinking the logical thing to do was put new ones in...... haven't ever replaced any in my other cars......

Anybody have some tricks, hints, or don't-dos for replacing the rails with the engine in the car? I have plenty of working room, and looks like a pretty straight forward job-
but ya never know..... any particular order to install, etc.....?

Many thanks as usual for all the help so readily shared on these forums...

Tim
'77 930

[kodioneill]

I use a prying type bar with a handle. looks like a bent screwdriver. carefully pry and pop them off. pay close attention to installation direction and placement of the ramps. are you going to replace the chains?

[Peter Zimmermann]

I use an old-fashioned brake spoon, an adjuster tool for drum brakes - it's a perfect pry tool to get behind the old rail (aka ramp, aka guide) and pop it out. Each rail has a long side and a short side; the long side points toward the nearest chain wheel (sprocket). The lower rail on the right side is a different height, and your replacement will probably be a different color than the other five.

To replace the inboard, right side rails you will have to remove the center engine mount pylon from the crankcase in order to remove the chain rail bolts far enough to replace their sealing washers.

I hate to mention this, but when I had my shop we never did a tensioner/rail job without also replacing the cam o-rings. That meant the cams had to be re-timed, but it also guaranteed that a sad customer wouldn't return in six months with an oil drip from you know where.

[Fast Corners]

Make sure that the inboard ramps are properly seated and aligned correctly. The specialized bolts have to screw into the ramps (which must be positioned correctly and supported in place) for the bolts to engage correctly. Take a good look at how the originals look before you take them out for comparison purposes.

I support the new ramps with my hand while turning the bolt in with a ratchet. This way you can feel it click in. If you don't feel it click in it is not seated correctly. If your ramps and tensioners are original then your chains probably are too and thus it would probably be a good idea to replace them as well. This gets into cam timing and like Pete says it is a good time to replace the seals then too.

One last note, put a clamp on the old inboard rails (like a vice grip or a big set of forceps which is what I use) and you won't have to fish a chain ramp out from a deeper portion of the case.

[chuckiii]

I have a '76 911S, completely original, 105K miles. Deveoped a sound in left side, sounded like cam chain rubbing on casing. removed left cover with engine in car, not difficult. Turned out this was exactly what was happening.

The lower guide (is this plastic or nylon) is missing completely. There are just two worn studs or bolts (never having removed and looked at this, they are plainly visible. I dont know what theses are supposed to be - a pair of bolts? or does the chain guide rail slip on and a circlip or something hold it in place? I cannot tell, because they are very worn and grooved obviously from the chain rubbing directly on them.

Where would the chain rail guide have gone - would it drop to a lower part of the main casing?

How do I replace the chain rail guide? Do these bolts (or studs ? its hard to tell, becasue they have become grooved by the chain passing over them with no plastic (?) guide ramp on top) unscrew (like grab them with a vise-grip, since there is no bolt head left.

Please don't laugh at my ignorance - i am no great mechanic - far from it - but will carefully follow any advice.

I know everyone says I should switch to a pressurized oil-fed system, but i cannot find one for less than $700, which I cannot do at present time. The chain is tight on top, but a bit loose on bottom - I can move it up about 3/4" lifting it off what remains of the old chain guide rail bolts. Oddly, there is no bits of aluminum or plastic or steel visible. Should I turn the left cam clockwise just a tiny bit (maybe 2 or 3 degrees), or does that not do anything (or does it harm something??)

I can send photo if it would be any help.

Any advice or guidance is very much appreciated.

Thanks.

Chuck
makoaleo@gmail.com

'76 911S targa
'77 911 S wide body conversion
'91 Carrerra
had a '68 912 soft rear window Targa
and a '68 912 coupe also