That should read: "Spin the engine clockwise by hand......"

the fact is you CAN let a portion of the chain go slack. that would be the section that the idler sprocket normally holds tight. as long as the engine and the cams remain in the #1 TDC position, nothing will change when the tensioner is removed and the idler assembly is removed. i've done 100s of them that way with no problems. the beginner could tie the chains up with a zip tie to lessen the chance of a mistake, but shops generally don't do that.

enlightenment please
 

I just ordered my tensioner upgrade parts from Wayne and will be doing the job in a few weeks.

One thing puzzles me. I have rebuilt a couple dozen engines of all kinds except 911 (timing chains, timing belts, timing gears, OHV, SOHC, DOHC, etc) and I don't understand why you would need a dial gauge to set cam timing. All those other engines had timing marks on the crank and cams. Set the marks and make sure the slack in the belt/chain is where it should be and you're home. Is there some fine adjustment that allows you to dial the cams in more accurately than that? What am I missing? Not that I would dismiss the opportunity to acquire another tool of course.

Re: enlightenment please
 

On a "normal" car like a 944, the cam and crank gear have marks that you line up when you set the cam timing.

On a 911 there is a TDC mark on the crank pulley but nothing for the cams sprocket. The cam sprocket is adjustable and the cam is timed such that a valve (#1 or #4 intake) is open a specified amount when the crank is at TDC. You use the dial indicator to read the valve lift.

-Chris

Wayne, in my opinion, you shouldn't recommend that people take this on without a dial gauge. Cam timing should always be checked before putting the covers back on. Furthermore, I think you should really emphasise turning the engine over by hand after the tensioners are installed. This should be a mandatory part of the procedure, not just check if you want at the end.

-Doug Clauder

just turning the engine over by hand to feel for interference isnt a "check" for properly timed cams. What could you do at best turning the engine over by hand? 4 RPM, then of course there are the thermal issues and acceleration of all these parts trying to work in unison. cam timing should be checked, then re-checked, with vise grips, clamps, blocks or whatever to take all slack out of the chain. When you can repeat the reading a few times in a row your ok.

Unfortunately this is a DIY'er like alot of us, and he had something go awry. And Wayne was his beacon to this upgrade

Hell I did a tensioner upgrade on my 2.0T, That upgrade morphed into a 9.8:1 full "S/906" improvement to my engine!!!. I followed the factory procedure to the letter.

When I started the engine after the tensioner upgrade, it sounded like a million bucks. I let the engine idle at about 1800 rpm for about 20 mins while I cleaned my tools and neatened up my garage.

So I take my car out for its first ride (post upgrade) and at 5800RPM I broke all the rockers on the passenger side of the motor!!!!!

I have no Idea why this happened ( well I do now because the cams in my engine were not stock)

I drove home on 3 cylinders, then started the $mucho dinero 2001 2.2S Porsche engine

One thing I think Wayne should stress is that the engine you are working on may not have the cams you think!!!!!!!!!! You have to know what kind of cam is in your engine before you time them!!


I knowBTDT

I guess I got lucky. This was the first project I performed on my SC, and it seemed very easy and straight foward.

Now adjusting the valves the first time was a whole different story!:eek: I bet I'm the only person to get them too tight, and not too loose the first time.:mad:

All,
Ah, been there, in my 77 911S, a tensioner failed , an awful noise. Living quite dangerously, I drove it home jacked the back end high and removed muffler, tin etc to have a look. Thought there was one chain but discovered a second , one on each side.
I had the rear end high as I had not drained the oil. Neither had I set the engine at TDC. I removed the right side tensioner and ordered the Carrera upgrade.
The following day, Val didn't like the threat posed to the kiddies by the high rear end so she lowered the car.
We had a large oil spill out the back but worse, as the rear wheels touched the gound, they must have rolled forward an this was enough to rotate the engine and the sudden tug on the chain rotated the cam and the chain jammed on the inner sprocket. I was not able to get the chain loose without removing the cam sprocket.
Got it all back together but not before learning how to time the cams.
Were I to do it again, along with all the good suggestions on this thread, I would mark the sprocket and chain before disassembly to be quite certain thay went back together in the same relative position as they came apart.
Ned Monaghan

Most Do it yourselfers dont even know what a dial indicator is never mind own one. I feel this would open doors to a more risky situation(they may read it incorrectely and start changing things that were allready correct). Also some dial indicators(like mine) are not metric which could lead to further confusion and a disassembled engine on its way to the trusty mechanic on a flat bed. When I changed my chains (see my tech arcticle) http://www.pelicanparts.com/techarticles/911_carrera_chain_tensioners/911_chain_replacement.htm
I had to read the timing procedure 3-4 times before I fully understood the procedure and I have owned and operated my own repair shop(no porsches) for over 12 years.


Kurt Williams

Please excuse me Wayne, I don't have your book yet.

I have done a lot of these. I mean a lot!

Yes, a dial indicator should be used. Get the holder too!
It doesn't have to be metric. If you can't do the math, there are a lot of conversion tables.

You should rotate the engine by hand at least 4-5 times between each camshaft timing adjustment. This is just to get accurate valve lift measurements. This is a must to get all of the slack out of the motor.

You can get to all of the cam chain ramps. It takes a little patience. You may even drop a ramp into the motor. No big deal, just take the sump plate off and push it out with your finger.

For an earlier poster:
The driving gear mechanism of a 911 camshaft allows for minute changes in camshaft timing in relation to crankshaft rotation. You can read the benefits of this from some of the Hot Rodding publications. Especially beneficial if you are a serious autocrossor.

The cam chain slip will always retard the camshaft. This allows the exhaust valves to hit the piston tops. Obviously, the expensive valves.

After looking a JW's post, I realize that I've never been able to R&R chain tensioners with out messing them up. I believe that it can be done without retiming the cams, however my level of expertise doesn't let me. JW is right in that the upper run of the chain if not disturbed, will keep the motor in time.

My guess is that if there is still compression, a light grind of the exhaust valve face will correct the problem and buttoning the motor back together would fix it. BTW, you will be using the dial indicator this time. The important thing is to get the measurements for both sides of the motor within the specified valve lift range and that they both be even!

Good luck,
David Duffield

I'm with old_porsche when he writes "The driving gear mechanism of a 911 camshaft allows for minute changes in camshaft timing in relation to crankshaft rotation. You can read the benefits of this from some of the Hot Rodding publications. Especially beneficial if you are a serious autocrossor. "... I found this out when I rotated the crank to recheck my cam timing, and found the cam timing had moved a hair.. this bothered me..I could not figure out why this happened, so I walked away from adjusting for the day..anyway, finally it hit me [not an expert] that the drive gears off the crank doesn't come back to the same chain link every revolution..I believe it took 9 or 11 revolutions of the crank to return the drive gear to the exact spot on the chain..then my timing matched up..good trivia................Ron

Ok, now you guys have got me worried. Didn't think it would happend, but it did. I'm about to do this procedure, what's the bottom line from the experts? Need a consensus, time cams or not. I don't have a Z-block, and I don't have the dial guage (although may be able to use one at the auto hobby shop...but I really don't want to do the job there), if the cam has to be turned, doesn't that also require another tool?

I can keep chains tight (I think), I can rotate the engine (clockwise) by hand. Is this enough? Also, if you do feel it bind, what do you do? You're no longer TDC, can't go forward, can't go back.

Bottom Line: Do I buy the Z-block and borrow the guage?

thanks

Rob...not a pro, but I would have a dial indicator and Z-block around to recheck cam timing [neurotically writing].. in spec twords retard/advance is another story, but I like to know that BOTH cams are the same spec..........Ron

This whole matter is silly, and you're all losing your heads. If you took 1 minute to think about how the 911 timing chain works you would understand that letting the chain go slack is not a problem and that cam timing has nothing to do with it.

Again, for those who care about how it works:

If the tension side of the chain does not skip a tooth then the timing is not affected one iota by changing the tensioners, or anything else on the "slack" side of the chain for that matter. If you want to be sure mark the sprocket position at TDC when you begin the job and check it before buttoning up. If the chain skipped a tooth on the tension side just get it back to the proper tooth and the cams will be perfectly back to the same timing they started at. Fine cam timing is only critical when you reassemble the engine and the distance or tolerance between the layshaft centerline and the cam centerline has changed or a new chain is used.

Umm, you *definately* should speak for yourself on that one!

Lots of us are not professionals, but do things a LOT more major than chain tensioners. And, I dare say, a lot of us do a better job than a lot of "professionals," many of who don't really care about your car and are not really very skilled.

These are pretty basic mechanical devices, not nuclear reactors.

Just a couple of notes to add here,

Several years ago I loaded up a cylinder with gasoline on my Ford racecar by accident, not realizing this I turned the motor over and blew the head gasket into the adjacent cylinder. Upon teardown I notice signs of the valves having touched the gasket but I didn't think much of it until I put it back together and it ran terrible. The compression test showed weak compression in that cylinder, I removed the head and discovered a very slightly bent exhaust valve. So in fact slightly bent valves can produce some compression. Second, if the cam jumped one tooth on the crankshaft sprocket that is the same as 1/2 tooth on the cam sprocket (cams turn 1/2 crank speed) I would have to believe that on a 9:1(approx) production motor that the valve pockets in the cylinder would be large enough to not hit a valve that's 1/2 tooth off but I could be wrong given the fact that while I'm an old hand at engines I'm new to Porsche engines. However a cam that is "out of phase" like this might allow compression losses because (assuming the valves did not hit) one of the valves would be partially open during the compression stroke, much like the lower compression shown on a full race cam. My advice would be to remove the timing covers and check the valve timing then perform a leakdown, or barring that perform a leakdown with the cam properly positioned via looking at the cam and not the engine timing marks (i.e. remove the valve covers and make sure both valves are closed for the leakdown) if the leakdown turns out OK I'd definately look into the cam timing. A perfect example of my experience with this is installing a timing belt on econobox 4cyl engines, they will crank over and sometimes barely run with the belt off by one tooth on the cam yet never bend the valves. Perhaps this individual can have another mechanic look at it for him or even perform these tests himself? The fact that all three cylinders exhibit close to the same low compression leads me to believe that the cam timing is in fact out by one tooth.

And as others have pointed out it is very important to gently rotate the engine by hand whenever the cam drive is serviced.

I made a "Z block" from a flat piece of steel with two holes drilled to bolt into the valve cover holes then used a magnetic base and dial indicator when I checked my 2.0E cam timing. Worked like a charm.

RoninLB is correct. Due to the length of the chan and the number of teeth on the cam sprocket, you must rotate the motor 9-10 revolutions before the same link will line up on the same tooth on the sprocket.

If the chain doesn't slip while installing new tensioners and or ramps, there is no problem. The question is probably, "How do I know if the chain has slipped?" After you have installed the tensioner and you rotate the motor thorugh by hand, if you feel any binding or that the pistons are hitting anything, you need to time the motor. Remember I said, rotate by hand with the spark plugs removed! Do it very slowly. Everything shoud feel very smooth. If It doesn't then its cam timing time.

This will not work on the 72T motor. I think this is the only motor that Porsche built which is a "free spin" motor. That is, you can rotate the crank without hitting the valves. I found this out when the son of a close friend called me. He was in tears. His father hand loaned him the 72T. The cam chain had broken and he had driven it home not telling his father. He was really worried about the damage he had done to the motor. The only thing hurt in the motor was the chain!

Good luck,
David Duffield