question on 575 cam timing

Its going to be at least another month or so before we start re assembling the heads on our 575 engine, but I took a look at the scribe marks on the back of the cams and the caps, they are all angled to some degree the same as yours. I would take it that the bottom of the mark on the cap corresponds with the slant at the top of the one on the cam in order to give a straight but slightly off vertical line?

 

I own a 1999 550 and it has rear cam marks so I would think most of them do.

 

Are you sure that the cap has not been mixed up? (not sure it's even possible)

 

I will rest the cams onto the heads on mine in the next few days then sit the caps on them and take a pic, as if they were installed and post it here.

 

Sorry for coming in late on this; I understand my cam curves & specs may have been adding to the confusion that Steve is experiencing. Hopefully I can clarify a few points rather than muddy the waters further.

First of all, any cam timing events, durations, etc. are always based on crankshaft degrees, not cam degrees. I don't know of any engine manufacturer that would specify otherwise, as it would cause extreme confusion to builders and hotrodders

Steve, I find this strange too, and it's different from the 550's spec. At TDC on Exhaust Stroke, the 550's intake valves are already supposed to be open 0.70mm, and the exhaust valves are still open too. This is what produces the "crossover" that Ferrari refers to, which is AKA as intake/exhaust valve overlap. The way I see it, there are two possible explanations for this anomaly in the 575M setup:

1. The -7 IO spec is correct, as this will result in the intake being closed at TDC on the Exhaust stroke, and there will be "no" crossover or valve overlap. This doesn't seem logical or correct to me, however, and I've never seen a high performance engine set up this way.

2. Both the -7 IO spec, AND the statement that the Intake dial indicator must read 0.0 at TDC on the Exhaust stroke are incorrect. This would seem to be the most logical case. You can confirm this since you are getting believable figures on your intake lifts at 18 degrees ATDC on Intake stroke; simply reverse the crank rotation until you're 50-60 degrees BTDC on Exhaust stroke, then bring it to TDC and read the dial indicator and see if it's 0.0 as the WSM specifies, or if it's some positive value (like the 0.70mm as per the 550's cams)

Remembering where you are in the 4 stroke cycle will help, and the cam/valve timing diagram is your friend here. What you're actually doing is measuring how much exhaust valve lift you still have at 18 degrees ATDC on the Intake stroke. As we all know, when you're on the Intake stroke, the exhaust valves will be closing (and rapidly), so if your exhaust lifts are greater than the WSM specifies, then you need to advance the exhaust cams to get them to close sooner., and conversely, if your lifts are less than the WSM specifies, you need to retard the cams. Study the cam/valve timing diagram and it'll be clearer.

All this is predicated on the assumption that the valve lifts are correct that Ferrari have published at 18 degrees ATDC on Intake stroke. As Brian mentioned earlier in the thread, you can confirm most of this by just setting the cams on the assembly marks and running through the procedure to check the figures, and I think you may have already done most of this, but I'd be very curious to know what lift you measured on the intake valve at TDC on the Exhaust stroke?

 

These are the rear marks on my heads when the cams are lined up with the marks at the front. Taken right to left. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

 

Paul, your cam plugs look like mine did Someone before me put an impact gun on them but forgot to use heat first (they're Loctited in there). Rounded out the internal hex nicely, which made for an interesting removal with an Easy-Out.

 

Ha, I did think they looked a bit chewed up! added some new ones to my ever growing list of parts to order in the next week or so.

 

So, you've confirmed the Intake valves are indeed starting to open at TDC Exhaust, and the Exhaust valves haven't fully closed, so both the -7 IO spec, and the statement about the dial indicator reading 0.0 at TDC are seemingly incorrect.

It would be good to hear from a pro who's been in a 575M and done this, to get another confirmation.

 

Given that these cars are tourers rather than racers I bet the vast majority have just been re set up as per the marks during any servicing works rather than ever being degreed, especially as they have no doubt run fine from the day they left the factory anyway on those marks.

 

Paul, I think once a Ferrari tech has satisfied himself that the cams are timed correctly, it's probably a lock & swap operation every time after that, until/unless something happens to change the geometry (valve job, surfacing heads or deck, etc.). Brian indicated as much earlier in this thread as the Ferrari flat rate book doesn't allow enough time/money to do much else.

 

That's retarded Literally......

 

John- Affirmative, and incidentally, the factory method worked fine on mine with all the marks lining up after degreeing cams using the WSM procedure. We also have 575M timing specs confirmed in the Superamerica (advanced 6 degrees) WSM. Int 575M -1/50, SA -7/56, Exh 575M 36/13, SA 42/7.

Too much thinking going on.