Hi all, I am in the middle of my cam timing process on my 550 Maranello. Thanks to all the info here on the forum, and especially the exceptional 40 pages posting of Moorfan, it has all been very straightforward. I even made 3 aluminum cam locks MSW developed a few years back, but afaik did not send into production. These locks made removing and reinstalling the cams in the correct safe position a straightforward job. The timing of the passenger side cams was easy, with a TDC tool and a curved tip feeler for the micrometer to measure 0.70 and 0.69 lift for the intake and exhaust. But: Before I started working, I measured all present timing, and the drivers side was 0.90 on the intake, so I was kinda happy to find a value that was a little off, so I could improve that. But now I know why that value is 0.90. The hole that the timing needs for 0.70, does not fit the locking pin! Only a hole that induces 0.50 fits, or the hole that induces 0.90. The 0.70 hole I really cannot get the pin to fit. Remarkable enough that position has been marked with a white dot. So I set all back to TDC on the passenger bank, so all marks on all 4 cams 99% lined up again, and removed the belt and cam cogs to see what was wrong. It turns out that the hole I need, is different! It is not 5 mm, but 5.5 mm, a little bit out of line with the other holes (placed higher), and not open on the back. (no idea if the passenger side is the same, did not encounter any problems there) The hole on the cam cog cannot fully line up with this hole on the cam, as it is positioned 0.1 mm too high. As the belt fences are fixed to the position of the crankshaft, the belt teeth are also fixed in position to the camshaft (when 0.70 mm lift is respected) and turning a cam cog a bit before reinstalling everything will not solve it, as in the end I still have the same situation. Anybody any idea what is the case here? Why is this hole different? Image Unavailable, Please Login
I do not have a 550, but on my engine we do use two pins per sprocket. As the second hole cannot perfectly line up, it requires a specific pin with a "slotted" tip (see ref 38). This specific pin is hard to come by. In order to use a regular pin instead of the slotted one, it is possible either to shave the pin or enlarge the sprocket hole... Maybe a machinist could fabricate a bigger pin? Given how your sprockets were butchered I would also install a second safety pin (slotted). A failure of a $9 pin could mean quite a few bent valves, so better to have one fitted in a proper hole! You could also line-up the cams as per the white mark and use two slotted pins on the adjacent holes? Image Unavailable, Please Login
Interesting thought, I can fabricate extra pins on my lathe for the 2 other holes as per your suggestion. They are 4.98 mm normally, and for this application I only need to shave one side for around 0.1 mm or so, so definately doable, thanks for the suggestion. By the way, the sprockets are not that butchered, I used some copper antiseize, which makes it look a bit ugly.
I believe the larger pin hole is a set up hole for manufacturing. That is just my idea. I have run out of holes for cam timing in the past (355s mostly) and I always move the cam sprocket two belt teeth at a time (as one tooth causes severe misalignment) and then try and find a hole that is close. This will have your punch mark on the pulley in the wrong place but the timing will be correct. On that set up, you should be able to find a combination that will get it right. Raemin is correct in the fact that 365 (Daytonas for sure) engines have two pins. The pins are also threaded internally so they can be pulled out. Back when Ferrari expected the engine to be serviced.
My comment was only about the hole and by no means regarding your own work. I have great respect for whoever pays attention to the proper timing of a V12...
Thanks both, so I should be able to find a combination when disregarding the sprocket mark, great. And installing a second pin is a good idea, as I noticed that even with a impact wrench to start the torquing, the timing shifts like 0.10 mm when the cam bolt is torqued. (and you need to start at 0.60 lift...) A second, slightly D-shaped pin should diminish that!
Turn your cam gear 180 degrees. The holes across from the holes you are currently using will split the difference and should give you the measurement you are looking for.
Post 4 and 7 are correct way to approach. Also there is lack of belt stretch from the new tight belt. You can't lay out a new belt folded in plastic since it left the factory like an old used soft one you can lay on the ground in a perfect circle. So when you get very very close to the hole you need you need to dial in some pressure on the cog to take all the slack out of the belt and insert the pin. The interference fit is very precise. You can't be off even a little and smash the pin home because the pins are not tapered but have a very small chamfer that does help insertion just a bit. The you need to rotate the motor and see if the timing is right and if not go the other way on the other really close hole. It is an iterative process and can take some time to dial it in.
Thanks all for the explanation and advise. I now understand that it was a coincidence that the pin needed to go into the one hole that cannot be used. I indeed used the old (nailpolish...) marks from some previous mechanic, which had encountered this problem and had chosen to use the next best hole, messing up the timing (0.90 instead of 0.70), so I found myself in the same circumstances that mechanic by chance landed into. (I only later noticed the indented marks on the teeth of the belt cogs when I had them off) So I rotated the cogs as advised above, and now the pins are in the holes where they should be, far away from the notorious larger hole. Timing is indeed a proces that takes time (...), especially with the exhaust cams as once the lift is measured, the only way to adjust is get back to TDC and pre-adjust what you saw that it was off the previous measurement...and then when the pin is in, and the bolt is tightened, and you measure again, to find that it is 0.05 off because of the tightening of the bolt has turned the cog (or cam)... I am sure experienced Ferrari mechanics do all this in 15 minutes where it took me 2 hours, but I am glad I did it. It was good to notice that even though the front cap marks do not line up fully (edge cap line on other edge cam line), the marks on the backs of the cams (the ones you can check with a mirror) do line up 100% (except for 1, that is scribed a bit unclear, will re-measure that today after the engine has been rotated a few times after a night of rest.
I have before just locked the cam on the number I wanted and then moved the crank to the position it needed to be in. I then put the pulleys and belt on and find the hole that lines up. If nothing lines up, I move the pulley two belt teeth at a time until I find what I like. I then slide the pin in place, set the tension and unlock the cam. After a couple rotations, I recheck and make any adjustment if needed. If it needs any it usually is only one pin hole. It is indeed a process. Having build many many engines and degreed hundreds of cams, it becomes very easy to understand what I am looking for and how to get it. It is much more difficult on early 308s that have only three holes in the cam and four in the gear. The more modern stuff can be put right on the number. I find it interesting that years later when I am doing an engine I have done before, the timing doesn't move. Makes me wonder why I have to do some many adjustments on engines I see the first time.
