Two dumb questions about cam timing.

Are the degree settings given in my owner's manual for degrees at the cam or degrees at the crank, which would be twice the cam degrees?

Also, does anyone have the dimensions for making a tool to hold down the bucket to get the shim out. I have a tool to open the valve, but I want to make a block or tool out of aluminum to hold the bucket down while I take the shim out for measurement.

Thanks.

 

crankshaft degrees

 

Are you sure Steve? I stared at the degree diagram for the 355 all night last night and I am sure it was cam shaft degrees.

And on the subject of the hold down tool, I loaned my out last week. the OP can borrow it if it comes back.

 

Borrowing is definitely easier than having one made. I am a tool and die designer, so I can draw one up very easily. Having it machined is a different matter.

 

The degree wheel is usually mounted to the crankshaft

Seriously, mathematically, either system could be used, but the values given in the 355 OM are definitely crankshaft degrees -- can you post the reference you are studying or where to find it?

 

This is the phase diagram of the 355. The diagram shows the closing and opening of the valves with respect to each other. It is definitely in Cam shaft degrees, which translate to 2 x crankshaft degrees.

I studied this all night because unlike Porsche manual which is written in a clear German precision fashion, the Ferrari manuals are written as instruction puzzles.
Image Unavailable, Please Login

 

Only if you've got an 8-stroke engine

Those are crankshaft degrees -- i.e.:

Intake opens at 16 deg BTDC and closes at 42 deg ABDC = 222 deg of crankshaft rotation after passing TDC for the first time (from TDC to "D")

With both valves fully closed, compression continues from 42 deg ABDC, firing occurs somewhere near TDC when passing by TDC for the second time, and the power stroke follows with the exhaust valve opening at 56 deg BBDC = 262 deg of crankshaft rotation (from "D" to "E")

Exhaust opens at 56 deg BBDC and the crankshaft returns to TDC (where it all starts over again) after 236 additional deg of crankshaft rotation (from "E" back to TDC)

222 deg + 262 deg + 236 deg = 720 deg of crankshaft rotation (2 revs for each firing of a 4-stroke cycle).

Alternatively, if that diagram is in camshaft degree, please describe where it shows that both valves are fully closed so that firing can occur?

 

That diagram represents the TWO revolutions of the crank that are served by one revolution of the camshaft. I suppose the arrows could be clearer, to visually show a sequence, rather than dimensions as used by tuner, but it is by far the easiest to visualize for me.

 

Steve,

That diagram shows a circle of 360 degrees, showing the profiles of the lobes as you move around the cam in a 360 degree circle. The values on the diagram are of degrees adding up to 360 degrees for one cam revolution.

You described a sequence of events adding up to 720 degrees of 2 revolutions around the crank shaft, which means the diagram is cam degrees not crank degrees.

Not a debate, but looking for clarification.

 

That is what I thought.

 

No, it shows the profile/action of the lobes as you move TWICE around the crankshaft -- i.e., event "E" does NOT occur when the intake valve is open.

Here's that same chart in a linear form (that's a lot clearer IMO):
Image Unavailable, Please Login

 

The angles and degree values are crank rotation, not cam rotation.

I've always viewed the WSM drawing is as two separate drawings, that were superimposed on top of each other.

The outer drawing shows intake cam timing relative to crank rotation, and the inner d rawing shows exhaust timing relative to crank rotation. This always made sense as you normally only have a dial indicator on one cam at a time.

 

yes, that is a lot clearer. Why can't they do that in the first place?

 

Because the way Ferrari does it is industry standard and is far clearer if you understand valve train operation. It is not linear, it has no beginning and end, it is continuous. TDC at top and the overlap period can be seen and judged instantly. BDC is at bottom and how far the valve events are from there can also be judged instantly. The circle is a perfect representation of what is happening. At a glance you can see everything you need to know.


The books are designed for people who know what they are doing, not automechanics 101.

 

All,

I am getting my repaired camshaft back and it has been recommended for me to index the cams. I would like someone could point me to a write up or at least a simple explanation of the procedure. I am not lazy or worried about the hassle but worried I may mess something up. My car ran flawlessly before I removed the cams and think that the process was done by a previous tech. I know this thread is like beating a dead horse but other than finding TDC (PM1) and mounting a degree wheel. I am having a hard time visualizing how each camshaft is measured to be correct. I am not as smart as Brian & Steve but I have had good luck adjusting the valves so if it pretty straight forward I shall attempt the procedure.

Once again thanks for any input or advice in advance.