1998 550 Maranello "sorting" thread--DIY

http://en.wikipedia.org/wiki/Piano_key_frequencies

In my quest for everlasting cheapness the squirrel cage started turning in my head. If you look on wiki the 88 piano keys each have a scientific name and frequency in hertz. I pulled out my kid's Seiko sat500 chromatic tuner ($30) which is used to tune her flute. It will listen to a sound and on the screen tell you if the sound is "C3" or "F#2" etc which correspond to a HZ frequency. So 126hz is between C3 and B2. 130hz is the 28th key on the piano if you tune by ear or "C3" as reported by the seiko tuner. These tuners are at you local music store just make sure your tuner breaks out the different keys of say "C" vs. some tuners that just register all 6 keys of "C" as "C". I hope that makes some sense. My thinking is you could strum your timing belt within earshot of the tuner and if it says "C3" you are at 130HZ. If it says "G#2" (G sharp 2) then you are at 103hz.

 

Sorry Pete, I had no intention to irritate you. This theory may explain. Bearings either seized or abnormally high build up resistance inside the bearing caused over heathed which transfered the heat to the belts caused stretching and meanwhile caused the grease leaked out. But both bearings toghether?, thats the question. Sark.

 

Pete, I don't think so as an instrument tuner often needs the tone to last a while, a belt stops resonating too quickly for it to work properly I think.

I used a magnetised paperclip, a coil from an old relay and an oscilloscope in great effect for this purpose.

FBB, the reason a sum of the two tensions is taken is because there is the possibility of having the long stretch tensioned correctly but still with a lot of slack on the other stretch; such because of the friction in bearings and cam lobes etc.

 

The musical instrument tuner didn't work for me a few years ago when I tried it. But I was able to tune an old guitar to the required frequency and pluck it, remember the note in my head and use a mechanics stethoscope on the belt close to where it contacts the pulley. I could hear the belt frequency when I thumped it and simply matched the two. Works well!

 

Cool adaptation... I remember 30 yrs ago trying to tune my Jag's six Webers with a 3 ft section of garden hose... A mechanic ( at Thoroughbred Motors as I remember) told me to start with the first carb- stick the hose in the throttle plate and the other end in your ear and remember the sound- tune the 5 others to the same exact tone and you're done.

Worked great- of course I was so poor I would have tried anything...

 

In those days I only had three webers(275) and sure wish I had known that trick then.
Thanks, I won't forget it.

 

I'll try to test the idea this weekend.

 

Pete, by any chance you can post a picture of the tool you used to lock the cams for belt chang. Thanks Sark

 

Pete, if tesion sets atumatically and lock it when spring streches maximally, how do you INCREASE the tension manually to reach the desire readings?. The other thing is WSM says rotate the engine twice, wondering several rotation streches the belt. correct me if I am wrong. Sark

 

I can see how this method can give wonky results. There is no WSM for the proper method of avoiding a wide disparity. A belt at the long side under mild tension in the driven direction could yield a very different frequency than the same long side with some static laxity that could be induced just from pressure on the camshafts from the relative lobe positions and the valve springs i.e. the reverse direction. There is always sort of a dwell, if you will, and no one tells us how to account for that. Perhaps the WSM idea of adding the measurements of the longside and the short side and the sum of the frequency being "X" is an attempt to equalize out this exact problem. But that is just a WAG.

 

Today I decided to take the timing cover off and check the over all belt conditions and also check the belt tensions with the Motoreva tool I purchased. The tension I recorded is 85HZ on the long side and 205 HZ on the short side of the belt. These belts and bearings are almost four years old. Cheking by hand might feel like they are little loose not very sure?. Also I found out that the pasenger side drive gear's inner fence is loose. what is next?.
sark

 

Pictures I took associated with the belt tension
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What is the 575/612 spec? Wasn't it something like 285hz combined? If so that's the dwell the factory might be taking out of the system by having that weird additive spec..

 

Well if I was using such a method we need to think of what the probelms are then how to solve them. My initial thinking is that the problem is that the belt tension changes with every degree of crankshaft rotation because the lobes of the camshafts place variable pressure on the belts through the cogs as the camshaft rotates through its motion. I "think" we can all agree that is where the primary variation would be. Now for solutions:
Pete you did some kind of average over several revolutions but if the stopping point is always the same place will the average be the right one? I'm not sure what you actually did. I'm thinking of 2 ways to do this.

What is you rotated one revolution and kept tension on the crank so that the cam shafts are firmly held in the driven direction then measure the long side? Do that for 4 revs and then average the number? Perhaps there is enough stichion in the system that keeping pressure on the crank in the driven direction is not required?

Method two: what if you left your degree wheel on and then measure the long side at cyl #1 at approx TDC the #2 at TDC then #3 at TDC then #4 at tdc ... etc. and averaged those numbers? Repeate for the 7-12 bank

Follow my pea brain logic guys:
Another question I have is was the 575 tension in the WSM of 126Hz with the old or new belts? TAZ? I'd like to know what a test 550 combined tension is long side and short side if the tension is 126 on the long side of the 550. Pete? If Pete's tension is +/-350 like the 612 then I am OK with that. However, lets say the tension was dramatically lower than 350 combined AND the 575 number was on the old belt style then we got a problem and the 126hz number is spurious. If TAZ is right that the new belt is stiffer then the harmonics totally change vs. the old belt and the old belt HZ frequency spec cannot be used. Pete could that have been the reason for your loose first set of belts? If the 575 OEM 126Hz spec is for the new belt and the 575/550upgraded/612 all have the same timing system and the combined Pete 550 at 126hz longside + xxx short side are no where near the OEM 350HZ then does that mean Ferrari is making up specs that sound good and that there is a wide latitude of what is an acceptable belt tension because we can assume there are plenty of dealer fixed cars running at these tensions 350combined or 126longside? If the answer to the last question is yes, that explains why for 30+ years I have been able to set belt tension by hand with 100% success because there is a wide variation of what will work. So now have I completely confused the heck out of you guys? Sorry I go no answers.

 

FBB- I have a very early 575 WSM I will check for an Assembly Number, but I think both the 126 and 330-360 numbers are probably correct. There is a good chance the last few 550s had the new belts, too, but no accelerated age testing was performed on the 550s.

Sark- The belts stretch and the Hz specs are only for new belts. Nothing in the tech data calls for rechecking tension.

 

It looks like the car used for the 575M WSM was Assembly Number 44064, which may have been the 34th 575M built. The AN for the belt change was 43847, so it looks like that precedes the WSM. So the 126 Hz and 330-360 Hz specs are both correct.

When I replace my belts in a year or so, I think I will also replace the tensioner springs. The same spring, part number 121249, $4.90 each from Ricambi, was used all the way from the Testarossa to the 612.

 

I instaled the John Deere ND alternater with swaped original voltage regulator, it works perfect. Thanks Cribbj and Pete for all the help I needed for this project. Also I should mention Taz and Fatbilly by helping me on other projects I had in the past. happy New Year to all of you. Sark