Removing 993 Cam Sprocket Bolts - Help Needed!

[earossi]

I need to break lose the cam sprocket bolt on my 993 3.6 motor. I do not have access to a proper spanner wrench to hold the cam sprockets so that I can break loose the bolt.

Can someone give me an acceptable way to do this without the need to go out and purchase either the cam timing locks ($200) or a spanner set up for the cam sprockets? I have the spanner wrench required for the old 1965 through 89 911's, but it is not the proper wrench to fit the sprockets on a 993. Very clever of Porsche!

[afterburn 549]

I will get scolded for this.....but I bought new nuts..I heated them a little and put my trusty air wrench to it...I was taking it all apart anyway...I did not care what i broke...If I was keeping chains and other stuff i would be more gentile...
SO...thats one way

[earossi]

Afterburn,

Thanks for your reply. If I were going to split the case and replace the chains, I would adopt your approach and use the chains to backstop the cams while I apply the required torque to break the cam bolts loose. Unfortunately, I am not planning on replacing the chains, so I cannot use that approach.

The fact that the sprockets on the 993 have (4) holes around the periphery suggests that the factory used a pin wrench to hold them in place while the sprocket bolts are torqued down. Unfortunately, I cannot find a listing for that wrench. So, the only way I know of is to use the camshaft locks which are a $300 item to lock the cams so that the bolt can be broken loose. Seems like a waste of good money for a one time shot.

Surely someone on this board has run across this same issue and dealt with it?

[afterburn 549]

I am thinking perhaps our host here sells a spanner wrench that would work...I have one..not sure if it will fit a 993....

[earossi]

Pelican does have a spanner wrench that they sell for the pre-993 motors......and I have that wrench. Unfortunately, the pin locations are on a smaller base circle than the 993 motor. What I need is an identical wrench (3 pin) with the base circle diameter to fit the 993. I have not seen that item in the Pelican catalog.

[Walt Fricke]

Ernie

I have always just used an air impact wrench to remove the early (large nut) and later (bolt) fasteners on the cams. You don't need to hold anything, even the crank, though I usually grip the chain with my hands. Impact is good. If this could cause chain damage, I have seen no evidence of it on my motors.

That's only half the job, of course. I have the tools for tightening.

Does the cam lock set the cam timing on these, or is that something which came along with water cooling and dual OHC?.

[earossi]

Thanks Walt. Yes, the cam locks set the timing on the 993 motors. The cams are locked in position indexed to the cam carrier. The crank is locked indexed to the intermediate shaft. With cams and crank indexed and locked, you then tighten the cam bolts and rely on the friction between the cam bolt and the sprocket to hold the timing intact.

I have decided to go back with the backdated arrangement that relies on the indexed sprockets that are pinned in place (1965 thru 1989).

I played around with the setup this evening and finally was able to fashion a strap that pegged the sprockets to one of the cam cover studs to freeze the cams from turning. With this arrangement in place I used a 24 inch breaker bar with a 19 mm socket to break the bolts loose. I feel that the chains did not take any of the loading.

[Walt Fricke]

Sounds like backdating would be required when using aftermarket cams with different timing specs. Or you'd need to fabricate a set of cam locks just for those cams?

With the older vernier pin system, it is still the friction from the clamping force which keeps the cam and gear together. I see the pin, with all its slop, as helping get you into the ballpark.

I'm sure Porsche had good reasons to drop the first cam attachment system with the big nut and the cam holder tool, and switch to the bolt and different tool system. But I had a lot more trouble getting things adjusted with the bolt system.

But at least it is adjustable.

[earossi]

Walt,

You are probably correct about the slop in the cam locking pin, but I would doubt that there is much slop. And, you don't have to harbor the fear that the cams will jump time enough to have an issue with valves hitting pitstons.

The locking tools for the 993 are anywhere from $600 to $1000, which makes them prohibitively expensive. And, with the cam lock system, there is no way to adjust cam timing to advance or retard it if you want to dial in a cam.

Since I am certain that the cam lock tools have machining tolerances to deal with, I would guess that they would introduce some slop into the timing system, engine to engine.

Lastly, the cam locks are installed on the back side of the motor at the bulkhead, and I do not think that you can install them with the engine in the car.

In the end, there is probably not a lot to be gained using one system or the other. I am backdating simply because it is more cost effective for me to do that since I already have the cam tools for the earlier motors. And, for some reason, I like the idea of being able to dial in the system......even though I may never do any dialing! You can assemble all the items you need to do the backdating from someone like Partsheaven (who I used) for less than a $100, or if you elect to purchase new chain sprockets, the cost would be about $300. The toughest part is that you would have to have key slots machiined into the 993 OEM cams. Most aftermarket cams come with the key slots already machined into them since the cam blanks are interchangeable fior a number of 911 models.

[berni29]

Hi

On my 993 (1994) the cams have woodruff keys and the sprockets are the multi holed indexed versions like as per a 964. However there were no pins in the sprockets. I am just about to do the timing using a 964 rocker and have ordered two pins to go in the cams.

Berni

[Flat6pac]

The 993 uses a 12 mm bolt about 40mm long, 19mm socket
Bruce

[jonathan2340]

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