Methods to find TDC?

If the drive gears had a 2" pitch diameter the lash would have to open up by almost 0.01" to have a 1/2 degree impact on timing. Bigger pitch diameter even more. But that would be pretty easy to check by clamping the drive gears and trying to rotate the crank. You would certainly want to do that before you put a new belt on and checked timing.

 

Fact: cam timing is done once every 5 years with the belt change many don't make the mileage.
Fact: cam timing takes an hour once every 5 years during your major. The rest of the major is 20 hours and often more.
Fact: buyers have been programed to ask for records and a PPI. Only the uninformed accept a belt change as a "Major service" nor understand the significance of a PPI that notes, "nail polish" on block nail polish on cogs?"

 

You guys get it. If none of this mattered we would be doing things the chevy way or just using some factory timing mark like our "assembly marks." We have vernier cogs with resolution at 0.20 degrees I think Ferraridriver posted. If the camshaft with assembly mark is 25mm and you made a mark for all 360 degrees the hashline is 1/4mm . At 50mm shaft the hashline is 1/2mm. So we are talking a hashline like a ballpoint pen line and while I don't have a camshaft in front of me that's pretty close to what I remember an assembly mark looks like. I can easily see 2 of those marks off by the thickness of a line. OK my eye is seeing 1/4 to 1/2 a degree with zero effort. The Ferrari lift method is easy to see on the dial gauge and to get the number they want you need that discrimination on the vernier cog and it is easy to achieve. So Ferrari has provided us with a method for extreme accuracy. Use it or not use it that's up to readers.

So from cams I have timed being 4 lines or 2 degrees off the assembly marks is seen and known. There are even pictures of such and more on Fchat from pros. I have posted that racing a 348 and playing with timing I could find no stopwatch advantage and Mitch on paper agrees. Well yes but I still want and should cam time to where Ferrari specifies. That is like a known basic...a reference point. We know that in even low horsepower/L Ferrari motors a few degrees off in cam timing can throw codes. Being off in cam timing plus other failing components compound the problem. This discussion was really about 355's. In 1995 100hp/L was a big deal and part of the reason for abandoning the 2.7 motronic for the 5.2 for superior mixture control. The 355 is like a race motor in a streetcar. Headers we know are junk for a streetcar but perfectly acceptable in a racecar where motor life is thought of in hours. We know that header failure seemed inevitable but seemed very random in the early days when the fleet was young and miles were few. An early theory as to why those failures were random is failures in mixture control assisting in earlier header death. It is going to happen but bad mixture just kills the headers faster. What do you need for ideal mixture control? Really good timing... In some ways the aftermarket headers have been kind of a bandaid. It allows us to be sloppy mechanics. At one time we knew of some 355's out there with a lot of miles and original headers. How did some guys beat the odds? Perhaps a really good mechanic?

So this all jives with my personal evolution in camtiming. I started decades ago as a Ferrari apprentice just using assembly marks and only assisted in the cam timing of the vintage race cars. Later I cam timed everything using a less accurate chevy method and it showed when a high number of cam timed cars ended with the assembly marks right on the money. Now doing the Ferrari method but on a lower volume of different cars (I'm getting old) my cam timing is just about never in line with the assembly marks but very close. Pros right here on Fchat were posting pictures of these assembly mark mismatches during early discussions on this subject.

One of the quietest most unassuming non-chest beater guys is Dave Helms. Owners quietly flock to his shop. When he used to post here his signature was, "quality is not an accident"



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Once again, "facts" get in the way. I have repeatedly asked why it is necessary. Other than the belt, which can alter timing by +/- 1/2 degree at most, what dimensional changes occur that can effect cam timing in an otherwise mechanically sound engine? Anyone? Bueller?

You know Dave, I was going to suggest something exactly like that. A linear position sensor synchronized with an angular position encoder. Rotate the engine a couple of times. Record piston position and velocity. Check the data. Note the angle where the piston velocity goes to zero and displacement is a minimum. Rotate the engine to that angular position and you at TDC.

Back in the early '90s we built a rotating rig with a shaft encoder that gave us angular position to within +/- 0.018 degrees. Gotta be good when it's for NASA.

 

The major reason Ferrari changed to 5.2 was because they were economically motivated to do so. They wanted to continue to sell cars in the USA and it was federally mandated that they be OBD II.

And I guess that if mixture control and throwing codes is so sensitive to cam timing then since cam timing can change by +/- 1/2 a degree due to belt stretch, and another +/- 1/2 degree due to thermal expansion of the engine, for a net of up to 1 degree, then all those "ghosts" that were throwing codes, requiring installation of the GCK to fix, were really the result of the cam timing being off.

 

You will twist words all day long in an attempt to prove your point. I support Ferrari's way of cam timing because their method is in the WSM. No where does the WSM say that cam timing is "only" for fresh assembly. Throughout Ferrari manuals all kinds of stuff are missing and sometimes just wrong. There was a discussion once on radiator fluid change intervals missing from the manual. It was silly to think since the WSM is silent on it that you would never change the coolant. Sometimes there is more to the world than just "the" math. Maybe some of you guys need to actually do these majors and processes will make more sense. My camshafts come out at every major. There are many reasons for this. To me getting those back in the right place is cam timing. Pro mechanics are all over the place with their level of practice. Yes Dave there are plenty who lock and swap. That does not validate your position. I'll counter your swap claim with the work of this pro who cam timed as evidenced by his manipulation of the vernier leaving behind witness silicone RTV instead of using a new O-ring. Oh well.. Image Unavailable, Please Login

Fact is Ferrari has a way. It is simple and take about an hour. The math is 1/20 =0.05 That's a whopping 5% increase in time. My wife has some nail polish bottles she does not need. I'm happy to send some your way.

Put your math away for a minute John. Why do you think Ferrari goes to all this trouble? 95% buy services like you so it isn't to confuse and put the 5% of us DIY guys on a wild goose chase. There were a couple enlightening threads on yellow banded Ferrari belts and dayco blue banded belts who makes both belts. Good sources in those threads claim Ferrari cherry picks the belts and we see fresh yellow banded Ferrari belts as the best. Your math would say it does not matter. Ferrari seems to think so...something about belts cut from the center of the drum is better than belts on the ends. Is it just a little more perfection in the timing system that you don't need? Calling Rutlands for a blue belt of Ricambi for a yellow one is the same effort. I buy the yellow ones.

 

WF

Well, as I said, diverting attention form the subject. Ferrari has a way.... Ferrari cherry picks belts... My wife has nail polish... No need to do any math.


Math aside, as you request, timing depends on the geometry of the belt system. For timing to change something has to change the geometry. What is it? What piece of steel or aluminum changes in length, diameter, or whatever? If you want to hang it all on belt length tolerances just say so.




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On cars that I have previously done a belt service, where I have properly timed the cams and know the history of the car, I will do a lock and swap to replace the belts. As John said, what can change that can alter the cam timing? Especially when the belts are 5 years old and the car has just sat in a garage with zero miles since the last belt change.

 

Dave, it does say this:

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Not exactly a how to. But here is the problem as I have previously tried to explain.
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You start approaching TDC at position 1. you rotate the crank to position 2. The gauge moves up. 1 was not at TDC. You rotate to 3, the gage moves up. 2 was not at TDC. You rotate to 4. The gauge moves up. 3 was not TDC. You rotate to 5. The gauge doesn't move. You're in the dwell. Conclusion: TDC is between 3 and 4. That's as good as you can say. Highly sensitive to the accuracy of the dial gauge because near TDC the piston motion is insensitive to crank motion around TDC. Wonder what the accuracy of AM 105784 is.

But yes, the 360 manual is specific about belt changes. Last time I mentioned that I was told I read too much. So there is all this stull left out of manuals that Ferrari says to do and when Ferrari puts in print that you don't need to do that their wrong?

 

I'm impressed that am 106177 appears to have a magnetic base that works on aluminum

 

Lol. It’s a ferrari tool they can do anything.

(I think it may be adjacent to the stud. For that matter why not just have a way to attach the cross bar directly to head stud.)


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Does anyone know ferraris method. Or was it discussed before.

 

Yes but that only fnds tdc. It looks lik in my manual it says 2.1 mm is when the intake should start to open 16degrees btdc and close 16 after.


Sorry actually say intake valve lift should be 2.1 mm btdc and exhaust should be 2.29 atdc. I think.

This is if I am interpreting the manual correctly

 

The Ferrari method is; " Ours not to reason why, ours but to do and die."

On the other hand,

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