400 head gasket problems - is the WSM wrong? | FerrariChat

400 head gasket problems - is the WSM wrong?

Discussion in '365 GT4 2+2/400/412' started by simonc, Mar 22, 2006.

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  1. simonc

    simonc Formula Junior

    Nov 1, 2003
    882
    Herfordshire, UK
    Full Name:
    Simon Campbell
    #1 simonc, Mar 22, 2006
    I am rebuilding my 1977 400 engine. The heads have been skimmed by the engineering shop to make sure they are flat and the block face is nice and clean. I have assembled the heads on the block and torqued them down correctly. The workshop manual says that the next step is to do an hydraulic test by closing off the heater outlet with a plate, fitting a blanking plat e to the front waterway outlets and then pressurising the water system with water to a pressure of 8-9 bar. I have done this using compressed air rather than water and I can hear air escaping up the cylinder head stud holes in the heads and past the head nuts. I have removed the heads, run silicone sealer around both sides of each head gasket around the head studs and refitted everything. Less air is escaping but the system does not hold pressure. I've checked that the domed nuts are not bottoming out, an d I've checked everything else I can think of. I took the heads off and took them back to the engineering shop and they confirm that they are flat and there is no reason to suspect the block is not flat.

    Th engineering shop have said that 8-9 bar is a huge amount of pressure for the head gasket to hold between the water way and the head stud holes. They checked with a Ferrari mechanic who also said the same and that he thought the workshop manual must be wrong and that the pressure should be 0.8-0.9 bar. This makes sense to me as this would be around the normal cooling system pressure but I have also checked the WSM for the 308, the Mondial and the Boxer and they all state that the pressure test should be done at figures between 7 and 10 bar. Could they all be wrong? Is the fact that am using air pressure rather than water pressure going to make any difference?

    The engineering shop suggested that I smear a new pair of gaskets with sealant, fit the heads, tighten everything up and just carry on. Obviously if this does not work it is a fair amount of work to pull it all apart again, plus the head gaskets cost me about $500 a pair each time I have the heads off.

    Anyone had this before or have any suggestions?
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    34,031
    Austin TX
    Full Name:
    Brian Crall
    #2 Rifledriver, Mar 22, 2006
    No sealant. Period.


    If you need it something is wrong.
     
  3. smg2

    smg2 F1 World Champ
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    Apr 1, 2004
    15,516
    Dumpster Fire #31
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    SMG
    #3 smg2, Mar 22, 2006
    has the block been faced or decked to insure it's flat also?
     
  4. miked

    miked Formula Junior

    Feb 7, 2001
    823
    Cincinnati, Ohio
    #4 miked, Mar 22, 2006
    I found it hard to believe that they call for pressure testing at 10X the normal operating pressure. I checked my 308 WM and there it is, 8 - 10 kg/cm" which is 114-140 psi. That is a lot!

    What about the cyl. liner projection above the block? Too much would keep the head from clamping along the mating surfaces of the block.

    I bet you are getting tired of torquing and removing a gazillion head bolts. Yesterday at work I had to torque a couple of bolts holding a machine to the mounting frame in the floor. Specs were 1500 - 2000 Nm! The torque wrench was over 6 feet long and two guys had to pull on it.
     
  5. andrewg

    andrewg F1 Rookie
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    Sep 10, 2002
    4,667
    Chester, England
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    AndrewG
    #5 andrewg, Mar 23, 2006
    It's also in my 400 & 412 WSM, although just had a chat to Robin my tech and he doesnt use that much pressure (and has done 2 full 400 rebuilds since we opened), but has suggested checking the block is actually flat.

    don't some of the earlier cars also suffer from leaks around the head bolts, which normaly settles after its run in? (just a thought)
     
  6. simonc

    simonc Formula Junior

    Nov 1, 2003
    882
    Herfordshire, UK
    Full Name:
    Simon Campbell
    #6 simonc, Mar 23, 2006
    MikeD - I have checked the cylinder liner protrusion and they are all right in the middle of the tolerances at 0.090mm

    AndrewG - I have checked teh block with a staight edge and it is flat

    I think I'll put the heads back on and see it it will hold 1.5 Bar, if it does I'll check the cylinders thmeselves can hold 10 Bar and then put it all back together.

    Simon
     

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