Setting valve installation height?

My understanding of it is that you are measuring the distance from the cam base circle face to the valve stem. You should be able to verify the distance from the cam to the valve stem tip with the cam lobe facing away from the valve stem. I think there is a Ferrari tool that mimics the diameter of the cam and holds the dial indicator and you set this tool into the cam journal in the head to measure this.

 

I don't know anything about 355/360 heads, but I made a tool similar to the Ferrari tool for my 308 by turning down a piece of aluminum stock to the exact diameter of the cam bearings, then cross-drilled it to receive a dial indicator.

When fitting the valves we installed a valve, along with it's bucket and a "reference" shim. then we put the cam on and measured the clearance. We ground the valve stem to bring the gap into spec.

Then we removed the cam and used the tool to measure the distance to the valve/bucket/shim. Using the reference shim allowed us a bigger landing area for the probe, which we rotated to get the minimum value. We now had a reference. Then for each subsequent valve we installed the valve/bucket for that cylinder along with the reference shim, measured the distance and ground the valve stem as needed.

Note that we used the bucket for that valve (along with the reference shim) for each subsequent valve. We suspected that there might be some difference in the machining of each bucket, so we did our measurements with the bucket matched to that valve. We assembled the heads with the valve/bucket set matched to each valve.

I realize the 355/360 valve arrangement is different and much more complex than the 308. Hopefully the procedure I explained will give you some ideas.

 

from an engineering perspective, that offset wouldn't have much of an effect on what you are trying to get with this measurement as long as the valve end is ground square to the valve stem.

The validation of the location of the end of the valve is to ensure you are still in the tolerance range for the motion of the valve bucket. You adjust the valve shims on the buckets for the fine adjustment when you shim the valves and then adjust the cam timing.

 

typically use something like this, reference is the spring seat.
https://www.goodson.com/Basic-Valve-Stem-Height-Gauge-Kit/

The factory way requires a factory tool, don't have one and not sure who may.

 

Considering that Ferrari has used this identical methodology for the last five decades, I would expect that most specialists and Ferrari-centric machine shops have the "tool" which is basically a length of rod stock with a couple of holes drilled in it. Other than the dial indicators, the tools are less than $10 to make. I can't think of a DOHC Ferrari engine that does specify the installed height as referenced from the base circle of the cam.

The WSM diagram shows "the tool" and the tool in use.

 

Ah,..

From an engineering perspective the same idea still applies. You are trying to hit the center of the adjustment range so that the tappet (hydraulic or solid with shims) is close to the middle of the range and prevent the tappet from bottoming out when cold. There is the same check on a solid lifter car like the 328 with the same .012" tolerance range.

The slight offset of the cam to the centerline of the valve doesnt affect that measurement much. Think of a triangle with a long side and a short side. Changing the short side length slightly has very little effect on the lengths of the long side and hypotenuse. I doubt you will get more than .002/.003 across the end of the stem if you swept the indicator.

 

Dave, with all due respect, I think your over thinking this one. Do it a described and you should be fine.

 

youre looking at it wrong. The measurement zero point is the center line of the cam or an inch or so above the valve stem end. Swing an arc from the center of the cam and see what you get side to side on that valve stem. (The end of the stem should be much better that 3.5 degrees from flat also )

If you measure it the way that Ferrari recommends... it is not nearly as sensitive to where you are measuring on the end of the stem.

if i get a chance later I'll sketch it up for you.

 

You're not understanding how installed height is measured. The lobe has nothing to do with anything.

 

More then one way to skin the proverbial cat, the reference from the spring seat is just as accurate as the spring seat pressure is based on the valve seat to keeper groove distance. As the seat wears the spring pressure will change. I'd have to look but all the WSM give an installed height for the spring, with that data it's not hard to calc' the wear of the seat.

 

I think what Dave is getting at is that the canted angle of the two valves still share the same center-line height from the valve tip, otherwise the WSM would specify the tolerance on those as well.

 

Wait,.... how many engineers are in this thread? this could get interesting.. from an engineering perspective that is..

 

I can see what DaveRocks is getting at. For the center valve the measurement is obvious. But for the side valves where do you measure to, The center of the valve stem? How would you assure that the gage was so positions? Perhaps the measurement should be made along the axis of the valve? Frankly, that would make more sense to me since the tappets are all the same and the idea is to provide the correct distance from stem tip to cam for the tappet to operate correctly.
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