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Thread: Installed valve height

  1. #1

    Default Installed valve height

    I'm carrying this over from the discussion that got started in Jtwlag's thread as I didn't want to hijack it.

    So for Radioman - I'm looking at the diagram in the WSM showing the measurements and it looks like I need a special tool to hold and zero my dial indicator. Are there any alternate methods or work-arounds?

    Also, if I am out of spec what do I do - trim valve stem, replace valve, replace seat?

    Again, any advice or guidance is greatly appreciated. TIA

    Paul

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    There are several ways to accomplish this. You can make the tool. This is what we did. You can measure, prior to disassembly, the height of the valve tip with either a drop gauge or using a " valve height micrometer." Or, in this specific situation, you could measure the valve tip height on a cylinder where the valve clearance is in range and the shim clearance is say 4.00mm +/-0.05mm. Keep in mind that you need to pay attention to intake heights versus exhaust, as the clearances are different.

    Presuming just a clean up cut was done to the valve seats...and the "margins" on the valve faces are within safe limits, precision grinding of the stems is a perfectly acceptable way to achieve the correct installed height.

    As the WSM is not always accurate or succinct on how/what the installed height should be, there is a alternate method. Although tedious, you can measure all of your intake shims. With the average known, the valve clearance known, as well as the spatial position of the cam base circle, you can then calculate your precise valve tip height.

    Having done this so many times, I can confidently tell you what your factory shim ranges are/should ideally be...

    I too started with Alfa. With the Alfa, the shim is below the bucket. With that set up, there is zero risk of a shim popping out or the cam lobe hitting the bucket. The cam lobe to shim/bucket geometry does not change. With the Ferrari set up, the importance of shim thickness versus installed height are far more important.
    Ferrari Service of Bedford, LLC
    "The Fluent in Ferrari Guys" celebrating 35 years of service excellence
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  3. #3

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    Thank you Raidioman. It seems I have a couple of options here. Having a tool made would not be difficult if I have the dimensions. The end sections obviously would be the same diameter as the cam journals so I really just need to know the diameter of the center section.

    Prior to disassembling my heads I measured and recorded all clearances and shim thicknesses so I know exactly where I started from. Just as you have said my shims ranged from 3.85 to 4.16 and I have all of the history of the car so I'm fairly sure the heads have never been touched before. What I did notice however was that almost all of my exhaust clearances were tight ranging from .259 to .305 The engine has 60,000 miles on it. The valves looked good and I just had the shop touch them up, check the heads for trueness and install new guides for me. Yes, I am sort of a compulsive DIY'er but only because I enjoy doing this stuff.

    Again, thanks for taking the time to give me a little guidance on this, I appreciate it. If you could possibly give me the center section diameter of the tool it would be a big help to me.

    Paul

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    You're welcome, Paul. I have written much on this subject over the last 10 years or so. Installed height is a big issue on a Dino....and gets even more complicated with the F355. Most of the QV and particularly the 328 head issues are related to the head gaskets leaking/seeping around the oil return passage.

    Looking at your shim range, the heads appears to "as they left the factory." It is normal for the exhaust valve clearances to tighten up a bit, as over time, they will recede into the seats. The seats will usually be fine after a clean-up, although the margins on the exhaust valves need to remain in specs. For all the QVs, the exhaust clearance should be .014-.016" or 0.35-0.40 mm. I tend to set them on the loose end of the specs.

    The tools are at my machine shop, so I do not have them handy....A measurement of the base circle is all you'll need. It may even been in the WSM, but I am not sure.

    Knowing where you started from is a great, great point of reference. You can replicate that point, just take into consideration the reduced valve clearances on the exhaust side.
    Ferrari Service of Bedford, LLC
    "The Fluent in Ferrari Guys" celebrating 35 years of service excellence
    **An independent facility with no affiliation with Ferrari SpA**
    Bedford, NH 03110
    www.fluentinferrari.com

  5. #5

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    Quote Originally Posted by Radioman View Post
    ....A measurement of the base circle is all you'll need...
    I think you're right, it looks that way in the WSM figure and it would make perfect sense.

    While pondering this I think I have come up with another method. Since I am able to get a reading on most of my valves using the thinnest of the shims I have and therefore calculate the shim size that would be required for proper clearance I can use that calculated size to determine how much lower the bucket would need to be to accommodate say a 4.00 shim. For instance if I calculate that I need a 3.71 shim to achieve my proper clearance then I would have to shorten my valve height by 4.00 - 3.71 = 0.29

    One more question if you don't mind - is there a limit on how much I can have trimmed off the end of the valve stem? Just taking a rough look at it the end of the valve stem stands about 3.25 to 3.50 above the top of spring seat and the keeper groove so there should be no problem trimming off half a mm or so as far as I can tell and so far it looks like it's going to be in that range.

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    Quote Originally Posted by kcabpilot View Post
    While pondering this I think I have come up with another method. Since I am able to get a reading on most of my valves using the thinnest of the shims I have and therefore calculate the shim size that would be required for proper clearance I can use that calculated size to determine how much lower the bucket would need to be to accommodate say a 4.00 shim. For instance if I calculate that I need a 3.71 shim to achieve my proper clearance then I would have to shorten my valve height by 4.00 - 3.71 = 0.29
    Absolutely. This method will work just fine... A few things to consider: Shim sizes (now) are nominal...They currently come on increments of .05mm. So, a 4.05 shim could be 4.05 +/-.02. Most shims will be at or under by .02 mm. Secondly, depending on precisely how you do your calcs, don't forget about the bucket thickness and location. And thirdly, don't get too carried away. If you're in the range of 3.85-4.15 +/-.10 mm, you'll be in great shape.

    Quote Originally Posted by kcabpilot View Post
    One more question if you don't mind - is there a limit on how much I can have trimmed off the end of the valve stem? Just taking a rough look at it the end of the valve stem stands about 3.25 to 3.50 above the top of spring seat and the keeper groove so there should be no problem trimming off half a mm or so as far as I can tell and so far it looks like it's going to be in that range.
    As long as you've got room above the keeper, there's no issue. This does not hold true with the Alfa, due to the shim placement.
    Ferrari Service of Bedford, LLC
    "The Fluent in Ferrari Guys" celebrating 35 years of service excellence
    **An independent facility with no affiliation with Ferrari SpA**
    Bedford, NH 03110
    www.fluentinferrari.com

  7. #7

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    Great, I just thought of another benefit. Since most of the existing shims I have are in the 3.90 to 4.15 range (I have a whole stack of 4.05's) I can have my valves trimmed to accommodate them and save some money. I already talked to my machine shop and they said they can do it no problem.

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    Funny....I've got 3-4 of most shim sizes, but 15 or so of the 4.00 mm ones.
    Ferrari Service of Bedford, LLC
    "The Fluent in Ferrari Guys" celebrating 35 years of service excellence
    **An independent facility with no affiliation with Ferrari SpA**
    Bedford, NH 03110
    www.fluentinferrari.com

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