Another Head Gasket question

Discussion in 'Workshop Forum' started by CnC79X19, Jun 13, 2019.

  1. CnC79X19

    CnC79X19 True Classic

    It occurred to me after seeing someone looking for a big fat head gasket in the FS&W section that we may need to correct something. Realized that we may have goofed up and want to fix it if we actually need to so I guess my question is "do we need to?" Our pistons are a cast set of 87mm oversized pop ups from Vic's installed after cylinders were bored to those dimensions.
    Bought some new dowels and installed the new gasket that came in our engine rebuild kit then installed and torqued the head not even considering the fact that the head gasket in the set is for the standard 86.4 1500 SOHC. Should we remove the head and look for a fat Race gasket as well and if so what size?? Opinions?
  2. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    See if you can find more info on the specific head gasket that was in your rebuild kit. Many of the head gaskets I've come across have a larger bore size and will fit over-bored pistons. Even a stock gasket allows for some over-bore and 87 is not that much bigger than stock. So I think you should be fine. With the spark plugs removed you should be able to turn the engine over by hand and feel no resistance between the pistons and gasket.

    As for the thickness, check to make sure the valves do not hit the tops of the "pop up" pistons. But unless the head was heavily milled, the pop ups are really tall, you have a radically tall cam, etc, your 1500 should not have interference issues that I am aware of. I'd do the same procedure, slowly turn the crank by hand (plugs out) to make sure nothing touches. There are better ways to check, but this should be the easiest. Just don't force anything.

    Maybe someone else has better suggestions, this is just how I would approach it.
  3. carl

    carl True Classic

    I'm going to assume that head gaskets are dimensioned to fit standard and accepted oversize pistons. I don't recall seeing head gaskets listed specific to overbore sizes. But...I'll wait to hear from folks who actually know what they are talking about.
  4. CnC79X19

    CnC79X19 True Classic

    Hey Doc, the standard according to the spec info provided on Vic's site is
    34.70 mm compression height and these pop-up pistons measure at 34.90mm. We're using a 1500 euro camshaft along with the euro head that was shaved slightly for trueness and these pistons have the small flycuts. I do remember that the head gasket seemed to have lots of room surrounding the cylinder bores, I just wasn't sure how much it would compress? Head is presently torqued but no cam installed so the turnover thing lcan't really happen yet. A little nervous to say the least at that project having never did it before. Actually less nervous finishing this transmission rebuild than tackling the valve thing
    Last edited: Jun 14, 2019
  5. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    Regarding the head gasket thickness. Many guys have built the same basic engine; Euro head, Euro cam, high compression pistons with small reliefs, and standard thickness gasket. In fact, isn't that what the standard Euro engine is? I don't recall anyone saying it made the 1500 a interference engine. But there may be exceptions? There was a recent thread where this was discussed and I recall at least one example had measured the actual internal clearance (valve to piston). It was fairly close but still not interference. And by interference I mean it would make valve/piston contact IF the timing belt broke and the crank rotated out of sync with the cam (e.g. valves fully open at TDC). Maybe see if Steve C has some info on this in his "Ultimate SOHC" write-up; he discusses a lot of Euro parts applications that we are not as familiar with due to the lack of them here. Also I'm sure other members with more experience in this particular set up will chime in.

    When it is time to set up the cam box and install it on the head, it will be easy to check for interference by hand with the cam cover off (to see the cam's position) and plugs out (for easy crank rotation by hand).
  6. CnC79X19

    CnC79X19 True Classic

    Thanks Doc. ChrisO just sent me some similar advice and didn't simply try to just sell me something out of his stock. In my books that type of stuff is stand up and he's made a client out of us here for sure. Nice to see​
  7. fiatfactory

    fiatfactory Steve Cecchele

    Western Australia
    1500 with Euro head, small flycut pistons...makes it an interference engine (only if you break the belt, so don't) and with around 1.4mm compressed head gasket thickness is about 9.8:1...with the euro 1500 cam and a 34DMTR/DATR/DATRA style carb and the dual out exhaust manifold is pushing about 90hp at the flywheel...great economy street engine.

    Head gasket std style is about 87.2 to the inside of the fire ring, some are 87.4 (but not many)

  8. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    Cliff, with several great responses that are much more qualified than me, it sounds like you are good. ;)
  9. CnC79X19

    CnC79X19 True Classic

    Hey happy on this end. Thanks Steve, Doc. Much appreciated
  10. tigeravg

    tigeravg True Classic

    Hangtown, Ca.
    Currently in this zone myself. My head has had the absolute hell milled out of it. Going with the thicker gasket from Matt, and it happens to have a slightly larger fire ring diameter (87.5) for 87mm slugs. I didn't do a crush test on my piston/valve space, but I'm guessing it may be reeeeeal close.

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