246 Cylinder Head Thickness | FerrariChat

246 Cylinder Head Thickness

Discussion in '206/246' started by SWSDino, Jun 25, 2019.

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  1. SWSDino

    SWSDino Rookie

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    #1 SWSDino, Jun 25, 2019
    We are in the process of prepping a 246 engine for a complete rebuild and cannot find the factory specification on the original head thickness. This engine has led a hard life with previous owners with suspect work being done by someone we suspect has a magnetic sign on the side of their truck "Today we do engines". We have the spec of the allowable material that can be milled (0.002 to 0.004 in.) to clean up the head, but at this point do not know if someone else has already milled it and by how much. No one I've contacted so far, including FNA, seems to know. This should be in a TSB somewhere, but where? Thanks, Steve
     
  2. racerboy9

    racerboy9 F1 Rookie
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    #2 racerboy9, Jun 25, 2019
    Steve, I have a NOS rear 246 head I can measure and show in a pic. I think you would measure from the cam cover face to the head gasket face if that makes sense. If you want certain measurements just let me know and I should be able to get them tomorrow.
     
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  3. SWSDino

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    #3 SWSDino, Jun 26, 2019
    That would be wonderful. And yes, the proper measurement is as you describe. That is the main measurement we need. Our valve seats don't look too bad, but a nice photo of a valve seat would also be nice. Ours have a "bronze" appearance, so we are not quite sure what material they are made from. My Alfa's all had a very hard steel insert and was unaffected when lead was dropped from fuel. Thanks, Steve
     
  4. racerboy9

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    #4 racerboy9, Jun 26, 2019
    I believe the valve seats are manganese bronze. I don't think unleaded gas is an issue with bronze valve seats.
     
  5. racerboy9

    racerboy9 F1 Rookie
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    #5 racerboy9, Jun 26, 2019
    I couldn't hold the Mitutoyo caliper and shoot a pic without it wavering all over the place but without the camera it seems to be 124.00mm measured is several spots.
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  6. SWSDino

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    #6 SWSDino, Jun 26, 2019
    Thank you so much for taking the time to get the measurement and take the photo. We picked up the heads today from being disassembled and cleaned at the machine shop so now we will measure everything and go from there. Thanks again, Steve
     
  7. TonyL

    TonyL F1 Rookie

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    #7 TonyL, Jun 27, 2019
    Not sure if that is going to be the best way to determine potentially how many times the head has been skimmed.

    Perhaps checking the combustion chamber volume may be a alternative / backup?

    According to some limited engine data I have here and translating Italian "Volume camera di scoppio" Combustion chamber volume = 50.375 cubic cm.

    Tony
     
  8. racerboy9

    racerboy9 F1 Rookie
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    #8 racerboy9, Jun 27, 2019
    I thought about checking combustion volume as well and that would be a good thing to double check. The fact that it is a NOS head and the reading is 124mm.00 on the button seems like it would be correct. I will check some of my other heads and see how they compare. Dennis McCann told me, years ago, that my method of measurement was the way to check if a head had been skimmed. Some shops skim a head as a matter of course but I wouldn't do it unless it was absolutely necessary.
     
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  9. TonyL

    TonyL F1 Rookie

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    #9 TonyL, Jun 27, 2019
    Racerboy9 - agree entirely and have no doubt your measurements are spot on - just thinking of another way to determine the overall accuracy as a double check
    Kind regards
    Tony
     
  10. SWSDino

    SWSDino Rookie

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    #10 SWSDino, Jun 27, 2019
    Measuring the thickness against the specification is the only accurate way of determining whether a cylinder head has been milled or not. There are just too many variables in using the combustion chamber volume unless one knows precisely the method the factory used. When "cc" the combustion chambers the goal is make all the volumes as equal as possible and slight adjustments are often made with additional valve grinding to change the "position" of the valve in the chamber. This is the first time I have run across the situation that the factory has not made available the head thickness. Doesn't make any sense to me to not publish the numbers in a TSB, if not the workshop manual. Appreciate all your responses, Steve
     
  11. TonyL

    TonyL F1 Rookie

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    #11 TonyL, Jun 28, 2019
    I have looked through all my tech data and yes unfortunately they haven't detailed the head thickness only CC volume
    Tony
     

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