348 Engine repair thread

I never intended my comment to suggest the marks are "off or wrong", they are assembly marks, not precision timing marks, that is the point I was trying to make. Assembling the cams to these marks is going to be "close enough" for some people.
If you are doing it correctly, you need to verify the cam timing as per the service manual. The cam timing is adjustable via the cam pulleys for a reason. Ferrari call them assembly marks, I have no idea why people are getting so defensive about it.

Further explanation about the 6˚ off.
When I put the belt on, the marks on whatever cam it was, would not line up, in order to get the belt on that particular cam was out by 6˚.
BUT, the mark would have possibly been "close enough" for some people.
I had to use the vernier adjustment to get the cam timing correct.
Perhaps I didn't explain it very well, I never meant the marks were "off" or "wrong".

 

I do think you're doing an absolute top job on your engine, very meticulous and thorough.

I am aware that sometimes I do not explain things very well. I think we all agree we want our 348's to be the best they can be, and your one most certainly going to be just that.

 

I have always found it amazing that Ferrari can grind a cam with multiple lobes and have the angular relationships between all those lobes dead on balls accurate but can't grind a simple notch in the correct position to assure proper timing.

 

They can, but cam timing is more than "lining up a couple of marks", there are other contributing factors like valve clearance and so forth which make the assembly/timing marks academic as in the real world of cam timing it needs to be based on dynamics using a degree wheel and dial gauge.
Its is the proper way to time camshafts.
Marks are great for the likes of a Toyota Camry, but Ferrari with their high performance race heritage and so forth, like to do things the "proper" way. I get that.

 

I agree that the marks may move after tensioning. That's why the dowels are there as you note. And you did TDC the correct way with a dead stop.

I have to disagree here. If the marks are correct, then lining them up sets the timing correctly. Valve lash is a different issue. If the lash is off, the timing in not necessarily off. As I'm sure you know, if you are going to degree the cams buy checking the angle where they start to open/close (as per Ferrari) the first thing you need to check is that the lash is correct. Of course, you can do as Eric did and use the lobe center reference and check for position of max lift which takes lash out of the picture. But as Eric found, when max lift occurred at the correct angle the marks also lined up. That eliminates the need for the lash to be correct , but if the lash isn't right the valves won't open/close when specified and you won't have the correct max lift, even though timing is correct.

My overall though here is that I'm not talking about +/- 1 degrees which is spec, and which may be difficult to see by lining up the marks, but the often repeated statement that these marks are off by as much as 5 or more degrees.

Fact is that when you degree a cam by any method all you are doing is lining up marks. For the max lift method you make a mark at TDC and then if the max lift is at XXX degrees you make another mark there and when you rotate the engine XXX degrees it better be at max lift.

 

I'm an old fart taught by Ed Iskenderian when I bought a cam from him in 1977, he would not let me leave until I proved I could center it. I was just a punk with an attitude LOL
He did the 10 before and after then check lash then correct it if off. I remember his cigar was killing me LOL

 

Okay, I don't think I am explaining it very well.
One of my exhaust cams was off by 6˚.
One of the other cams (I can't remember now) was out by 3˚ or something like that.
If you looked on certain angles (Parallax error) then it looked almost right, some people may have taken this as "about right" carry on.
I was unacceptable to me so I went checked the timing using the center-line method.
I adjusted the timing then everything lined up perfectly.
I don't know who said the marks are off 5˚, but that is not correct and has nothing to do with what I am trying to say. The marks are assembly marks, call them timing marks if you want, but if you are actually timing the cams, you don't use the marks, you use the dial gauge and degree wheel, then marks will line up if you have it correct.

 

Ok, you convinced me. I did some calculations and at the radius of the timing marks, the mark would move about 0.15 mm around the circumference per degree of crank angle. Given the width of the marks I can see where it would be difficult to set the timing better than say, +/- 2, maybe 3 degrees at best. Even if the marks are correct, they lack sufficient sensitivity to angular movement. I see that they would have to be like micrometer fine, or at a much larger radius to be used to accurately set timing. The problem I have struggled with is that I have seen pictures of supposedly correctly timed cams where the marks completely misaligned, something like this. That would have to mean the marks were like 8-10 degrees off. I don't see how the marks could be that far off unless Ferrari was totally wack.

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So the way I now see it, lining up the marks visually won't necessarily give you perfect timing, but after setting the timing with a degree wheel, the marks should visually line up.

Thanks for a useful discussion, Kevin.

Eric, sorry to temporally hijack your thread.

 

Finding TDC is another issue.

 

This is why lock and swap does not work for accuracy despite the theoretical prior discussions we have had that lock and swap works.

That's the chevy way. There are many posts by RifleDriver (an indy once FNA mechanic who most know on these boards) has told us dead stop is not the Ferrari way. So dead stop is not the "correct way" for Ferrari motors and those degrees matter but 99.9% will not feel a difference. Maybe on a race track with a stopwatch with a driver who can repeat laps within a few 10ths? If we are going for accuracy then doing it the Ferrari way makes the most sense.

 

You are so right! This is why after timing with degree wheel so many of us have posted how the timing marks are dead on. Yes mostly mechanics have posted when they were off like your picture but I think those are the man bite dog stories to drive home their agenda about cam timing. I think in my experience working on Ferraris that mostly are stock unmolested examples needing routine maintenance we see those marks dead on but there are degrees in those lines that to use your words "lack sufficient sensitivity to angular movement." I have tried to explain that to you before but could never do that as well as you have just done it.

When you are actually cam timing you can get to just about where you want to be and then you find the pin will not go passively into any cog hole. You have to get your pin very close between 2 holes and tweek the cog just an RCH and drop the pin in passively. Then you recheck the timing to see if you are right. That's that "micrometer fine" that is barely perceptible. Sometimes your timing is off and you have to pick the other hole. It is an iterative tedious procedure and you don't see that couple degrees shift in the assembly marks lining up as you state.

 

Hi Carl,

How TDC is done isn't an issue. Either method done correctly is satisfactory. However, the Ferrari method is more error prone.

Lock and swap, well we disagree, and so it will remain.

 

Satisfactory perhaps but it introduces an error at the start of the process. Everything is wrong after that. I still believe if not doing right why bother?

 

Yes, the Ferrari method is somewhat ambiguous. I'll give you an analogy. As ball is rolling across . the floor. You have a watch. You are watching the ball. Can you tell me the exact time the ball stops by observing its position? (Ignore any reflex times).

 

Thank you too John, its great how we could discuss this objectively without getting totally out of sorts. You did an excellent explanation, and the diagram helps explain it.
The width of the marks, and parallax error are the two things which can contribute to the accuracy or lack of accuracy of the marks. But essentially, I believe they are absolutely bang on correct, can't see any reason why they wouldn't be.

To do the cam timing, I prefer the centre-line method, it has always worked well for me and I think most people would agree.

I would say if those marks are "not quite" lining up, the cam timing is going to need to be adjusted, and lets also remember the cam timing is adjustable only in 3˚ increments.

Yes, sorry Eric for totally hijacking the thread of your most meticulous ever engine service.... It must be getting close to D Day!!