Kevin in Atlanta

What are the pros and cons?

jcorenman

Keep. Cheap insurance.

GregBBRD

....Porsche engineers didn't put these pieces there because they had extra parts laying around, to use up.
Armchair engineers telling people to remove them are....not very smart.

Regardless of what tensioner design you use, the lower roller helps keep the belt from jumping teeth, if the engine rotates backwards.

Porsche went back and forth between the single roller and the double roller. The GT engines have the double roller. The GTS models went back to the single roller.

With today's slightly thicker factory cam belt (or Gates), you may want to use the single roller, instead of the double roller assembly. (I do.)

The second roller (on the oil pump side) sits closer to the crank gear and can spin all the time. Sounds just like....a small bearing spinning too fast. (Exactly what is happening.)

And because the sound radiates everywhere...and you can't see that roller spinning, you can spend hours trying to figure out what is making that terrible whine.

Ask me why I know this....

Kevin in Atlanta

That matches my memory of what you wrote in the past. I recall you tossing idlers - so it must have been the 2 roller version in favor of single roller version.

FredR

Notwithstanding GB's accurate account, as I recall there was a thread where someone posted how the cam belt had jumped several teeth and it was noticed that the lower roller was missing "omitted" by someone who was guided to think it was not needed. The tensioner system works well under normal circumstances but in the [very rare?] event of a backfire the tensioner simply put does nothing in the immediate aftermath. The roller as designed effectively ensures the belt stays in contact with the cam sprocket if there is a tendency to lift off - the word "back-fire" is used for a reason- the engine spins backwards if it fires prematurely/falsely during a start. Whether or not the motor suffered any valve damage I cannot recall - I have a feeling we never read about the outcome! The motor was that of the S4 category [i.e. interference].

That was a classic example of "if one does not understand it do not dick around with it".

Adamant1971

IIRC that was the car that rolled back in gear and then the belt jumped teeth on the crank gear.

Another vote to keep it.

linderpat

Car rolls backwards, even a bit, you can have a problem.

namasgt

I kept mine on this recent timing belt job. The bearing was seized up a little. Don’t think the belt ever touched it.
so did the 85-88 come with the single roller then the 89-91 S4/GT had double roller and 92-95 They went back to single roller (assuming same part used on the 85-88)?

Im pretty sure my 88 has the single roller but can’t remember.

FredR

My 90S4 motor has one single roller but then it was 8 years old when I acquired it.

FredR

Quite possible if it was a manual- but not a feasible possibility on an automatic or so I would think.

Adamant1971

Yes. And for that reason when my car is parked on an incline with the *** down I always put in reverse not first.

RDON

[QUOTE
With today's slightly thicker factory cam belt (or Gates), you may want to use the single roller, instead of the double roller assembly. (I do.)

The second roller (on the oil pump side) sits closer to the crank gear and can spin all the time. Sounds just like....a small bearing spinning too fast. (Exactly what is happening.)

And because the sound radiates everywhere...and you can't see that roller spinning, you can spend hours trying to figure out what is making that terrible whine.

Ask me why I know this....[/QUOTE]


Greg,

I’m in this exact roller spinning situation with a Gates belt (not long life or racing) and yes, its difficult to locate this very annoying noise. My plan was to replace with a genuine Porsche belt but you seem to indicate that I’ll have the same issue with the factory belt. Has this been your recent experience?

I appreciate your response to Kevin, it appears that you’ve just saved me from a lot of unproductive work!

Thanks,
Roger

Mrmerlin

if the rollers are touching the belt you can see witness marks on the back of the belt

GregBBRD

Greg,

I’m in this exact roller spinning situation with a Gates belt (not long life or racing) and yes, its difficult to locate this very annoying noise. My plan was to replace with a genuine Porsche belt but you seem to indicate that I’ll have the same issue with the factory belt. Has this been your recent experience?

I appreciate your response to Kevin, it appears that you’ve just saved me from a lot of unproductive work!

Thanks,
Roger[/QUOTE]

Yes, you will have the same problem with a factory belt...Gates makes both on the same equipment.
Simply remove the double roller and saw off the metal bracket just beyond the OD of the second roller. (If you do this carefully, you will end up with a spare roller/bearing.
A quick "touch up" of the sawed end on a grinder or belt sander and you end up with what a single roller looks like, from the factory.

Re-assemble and you are done. And that irritating high speed bearing noise will be gone!

Need pictures?

RDON

Pictures would be great!