928er

there is no getting lucky with the variocam and a broken timing belt. I marked the timing belt through the viewports and then cranked it by hand..... it rotated too easy for an engine with the plugs in..... timing belt didn't move on either exhaust cam.... more than likely stripped teeth on the belt where it goes around the crank pulley...

CraigL

Porkensioner or stock belt tensioner?
Good luck with your findings.

fraggle

Neither, sterling's setup is one of one. Sorry to hear it, mate. I was going to say you'd raise your man points by the power of 2 for pulling It twice but you're already way beyond that for the build itself.

Bill Ball

OK, so you're certain some of the valves are toasted. John's car did the same thing. The cams did not move when I turned the crank. We found 12 stripped teeth lying in a pile down near the crank, And he stripped the belt while driving on the freeway. Still, no valve damage. But, of course, he doesn't have Variocam.

Anyway, I'm very sorry to hear this. Seized water pump was the cause in John's case.

Tom. M

I cranked the **** out of my engine before I knew I stripped the teeth off the belt at the crank......

Only two valves ....good luck ..

928er

Tom, did you figure out the cause?

Tom. M

When they rebuilt the top end the first time (PO) they didn't rebuild the tensioner and it had cracked belleville washers and no oil..so even though the tension was spot on with the kempf tool...I don't think the tensioner worked as it should ( eg. loosening when hot). This led to the wearing of the coating on the cam gears, which in turn were so sharp they cut into the edges of the teeth on the belt. The belt upon closer inspection had micro cracks at the base of each tooth..

We had just driven over to Spokane for our semi annual Track Attack and car was very hot...took it up to the local grocery store to grab some beer for the gathering...came out of the store..and cranked it....the car almost wanted to start...but didn't...I kept cranking thinking vapor lock or whatever... finally gave up..got towed back to Chris F's house..and we were all trying to figure out what was up... Louie had the piece of mind to check the cams through the holes..and sure enough..no turning while cranking.

Got the car towed home and put on an old belt..did compression check...started at 8...worked all the way through and finally all was good...until we got to 4.....passenger side rear... gave a reading of 0...

When I pulled that head..couldn't even tell the valves were bent..except for small bits of carbon missing from the valve....

90 S-4

Sterling,
Is it an OEM belt or aftermarket

heinrich

Joe I have never heard of a belt failing because of the belt. ALL belts are good. They fail because of abuse from something else, worn rollers/gears; slack in the tension system (often a result of water pump or idler roller or tensioner issues); or overtightening / undertightening.

GregBBRD

That sucks.

But, as you know, when you are developing new technology, things can go wrong.

Good luck. Yell if you need any help figuring it out.

IcemanG17

DAMMM......this has been a LONG project for you...... I hope the 928 gods smile upon you...which seems to be the case lately....at least for Charley and John....

blown 87

You mean OE or aftermarket I think.

heinrich

We all know by now, Sterling isn't going to make any money selling Variocam 928 conversions. IMHO this decade-and-a-half project might have been, and still might be, more successful if information were openly shared, and we all got the shot at trying to do it ... that way there would be more than just Sterling working this thing. and who knows, we might have a solid 928 Variocam by now.

GregBBRD

"Internet engineering" very seldom works. While some ideas can be helpful, these are far and few between.....and you could spent your entire life doing something as many ways as there are ideas.

Sterling seems very "solid" mechanically, but glitches are bound to happen. When you are doing straight "mechanics", things go wrong. When you are doing developmental work...the odds of "problems" go up exponentially.

Look around and count the number of stroker engines that are actually running...compared to the amount of cranks that have been sold...and the reality of this becomes apparent very quickly.

heinrich

Greg, looks like the alternative has not helped our friend Sterling in the least ..... 15 years, hasn't it been?