F355 Measuring Valve Height (Seat wear / valve replacement) - Ferrari Life
 
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post #1 of 12 Old 06-24-2015, 09:25 AM Thread Starter
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Measuring Valve Height (Seat wear / valve replacement)

Hey Guys,

So, it appears Ferrari sets the valve tip height based on the CAM bore (makes sense as this is a function of lifter travel).

See the image from the WSM.

I have a feeling I will be designing and building another tool as you can bet this won't be on a shelf anywhere

Now, here is my question: If I install new valves and dress / lap the valve seat, the valve tip will get closer to the cam. So, can I grind the valve tip to maintain the dimension shown? If I do, I will also be effective the spring force but that must be a moot point because the amount will be negligible?
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post #2 of 12 Old 06-24-2015, 12:30 PM
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Installed height is critical in all Ferrari applications. The WSM is quite explicit on how it's to be achieved. Make the tools and measure the installed height. If you need to grind the valve ends, the spring force is not effected. Simple, easy...but takes some time to get it right.

The tools are often still available, although the last one I priced was over $700, without the dial indicator. Seems a bit steep for round stock with a hole in it...

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post #3 of 12 Old 06-24-2015, 12:40 PM Thread Starter
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Originally Posted by David @ FluentInFerrari View Post
The tools are often still available, although the last one I priced was over $700, without the dial indicator. Seems a bit steep for round stock with a hole in it...
Hey Dave, I found it strange the WSM did not list a tool P/N so I have inquired to see if one exists and the cost. It seems to me the measurement is from the cam lobe at dwell to the valve tip. For the exhaust valves and center valve that is a tool as you describe. But for the lateral intake valves it's a tad more tricky as those are compound angles. My tool will have a sleeve to pilot on the valve stem for alignment before taking the measurement. And, I will need another sleeve to zero the indicator before the proble exits the hole.

As always, thanks for your reply.
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post #4 of 12 Old 06-24-2015, 12:44 PM Thread Starter
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PS, I know my OCD is coming out again but if the valve position moves up or down based on the seat, the spring force would theoretically change. F=KX. K being spring constant and X being compressed distance. But as I said, I'm guessing .005" or so is too small to matter and the springs are not precision enough.

Sorry, just overthinking again
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post #5 of 12 Old 06-24-2015, 01:23 PM
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Quote:
Originally Posted by dave rocks View Post
PS, I know my OCD is coming out again but if the valve position moves up or down based on the seat, the spring force would theoretically change. F=KX. K being spring constant and X being compressed distance. But as I said, I'm guessing .005" or so is too small to matter and the springs are not precision enough.

Sorry, just overthinking again
OCD or not, your thought process is still flawed. The valve position remains constant. The stem above the keeper is ground, hence affecting the height of the lifter in the bore.

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post #6 of 12 Old 06-24-2015, 01:32 PM Thread Starter
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Originally Posted by David @ FluentInFerrari View Post
OCD or not, your thought process is still flawed. The valve position remains constant. The stem above the keeper is ground, hence affecting the height of the lifter in the bore.
Sorry Dave, true but not. When the seat is cut the valve moves up and so do the keys and retainer
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post #7 of 12 Old 06-24-2015, 04:23 PM
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I get $1200 a day when the talk gets to this point, maximum day is 4 hours including lunch and breaks.



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post #8 of 12 Old 06-24-2015, 05:50 PM
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Quote:
Originally Posted by dave rocks View Post
PS, I know my OCD is coming out again but if the valve position moves up or down based on the seat, the spring force would theoretically change. F=KX. K being spring constant and X being compressed distance. But as I said, I'm guessing .005" or so is too small to matter and the springs are not precision enough.

Sorry, just overthinking again


Which is why if the measurement isn't in spec you have to either grind the seat more (if greater than spec max) or replace the seat (if less then speck min).

If you are going to tell someone how to remove a bolt you should at least know which way to turn the wrench.
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post #9 of 12 Old 06-24-2015, 06:13 PM
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Sorry Dave, true but not. When the seat is cut the valve moves up and so do the keys and retainer
Installed height and spring loads are two entirely different topics. You asked about installed height. The correct answer was given. The spring is not even in the equation during this measurement. The spring load is adjusted, if need be, with shims, new valve seats,valves etc. Frankly, considering the miniscule amount of material that would need to be removed from the seat, that situation of shimming the spring is extremely unlikely. The valves are a throw-away as there virtually no margin to work with to begin with.

The installed height is adjusted by grinding the end of the valve. Notice the diagram Ferrari provides.

The reference to replacing the valve seats is an extreme case where either multiple valve jobs have taken place in the past or, more likely, the seats were severely over-cut.

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post #10 of 12 Old 06-24-2015, 06:23 PM Thread Starter
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Quote:
Originally Posted by David @ FluentInFerrari View Post
Installed height and spring loads are two entirely different topics. You asked about installed height. The correct answer was given. The spring is not even in the equation during this measurement. The spring load is adjusted, if need be, with shims, new valve seats,valves etc. Frankly, considering the miniscule amount of material that would need to be removed from the seat, that situation of shimming the spring is extremely unlikely. The valves are a throw-away as there virtually no margin to work with to begin with.

The installed height is adjusted by grinding the end of the valve. Notice the diagram Ferrari provides.

The reference to replacing the valve seats is an extreme case where either multiple valve jobs have taken place in the past or, more likely, the seats were severely over-cut.
David, point taken. Yes, I understand the effect on spring force is very minor and based on the spring accuracy it was a moot point. And yes, you are certainly correct that I was wrong to view this as an assembled dimension when it's just the valve tip to cam dwell.

As a side note, if you have this tool, a photo would be great. As I said, the lateral intake valves make the tool much more complex the the center intake and both exhaust valves that are not a compound angle.
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post #11 of 12 Old 06-24-2015, 06:32 PM Thread Starter
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Quote:
Originally Posted by David @ FluentInFerrari View Post
The valves are a throw-away as there virtually no margin to work with to begin with.
To this point, I was discussing this with John last night. From my poor memory, when designing and building equipment for GM, I recall the margin to be much larger. I was rather shocked how little it is on the 355.

In fact, I have records of this car (very sloppy) from a one man shop in Florida. Per the records, the car had some new guides and a few new valves. Now, until I inspect all I can not be certain but I don't buy it based on what I'm seeing thus far. It would be hard to believe the seats have been cut aside from the original build at the factory.
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post #12 of 12 Old 06-25-2015, 09:48 AM Thread Starter
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David gave me a tip a few months back to download the 360 WSM. He said the motor is very similar to the 355 and the WSM is much better.

I've been having trouble downloading from Ferrari Data Base but I did manage to get part of it today.

In the manual, they do reference to tool (CS 7148) but to my knowledge the 360 does not have valves at compound angles. However, the manual states the measurement is from the camshaft seat (bore) and not the lobe dwell. So, for the lateral intake valves of the 355, I suppose I can do the math to extrapolate the dimension for those valves at the angle (once I measure the angle).
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