Which thermostat gasket to use?

Discussion in 'Workshop Forum' started by carl, Jun 12, 2019.

  1. carl

    carl True Classic

    Location:
    Virginia
    I recall there is an issue, at least with some heads, that if you use the wrong thermostat gasket you get coolant into the intake...I know this happened to me once years ago.

    I was putting my motor together today and found the thermostat gasket that was on the thermostat housing is different than the new gasket (from an FI gasket set).

    IMG_0976[2].JPG
    The gasket on the right is the old one and the one on the left is the one that came with the gasket set. The old gasket matches the opening in the thermostat housing but the new gasket matches the head. The thermostat housing came from the motor that was spitting out thrust bearings and I want to use it on this new motor as the thermostat is new and I know this worked great. I note the fourth hole in the thermostat is a blind hole.

    Two more pics below.
    IMG_0977[1].JPG
    IMG_0978[1].JPG

    Middle pic shows the head and the lower pic shows the thermostat with the new gasket.

    So, the question is, am I safe using this thermostat and new gasket on the FI head?
    Anyone know what X motor this thermostat housing is from?
    Was the water in the intake just for the 79/80 carbed heads and this is all a moot point if I don't have that head?
     
  2. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    In my opinion you could use either gasket in this particular situation.
    The T-stat housing you pictured went to a head that had this hole in it:

    160.JPG

    If you used that type head then it would matter because you do not want water traveling into that hole. So you would need the gasket that looks like the old one you took off. On the other hand, with the head you are using (no hole in it), the T-stat housing normally does not have the corresponding blind hole in it, and the new gasket you have is correct. But so long as the gasket seals the T-stat housing, and there is no hole in the head for water to get into, then it does not matter which style gasket you use (in my opinion).

    There is a good thread that details this subject with pictures and explanation. But my link to it isn't working for some reason.
     
  3. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    Maybe this thread Dr Jeff? It is on topic at the minimum.
     
  4. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Thanks Jim. Actually I think it was a different one. When I try my link to it, it comes back saying "your file was not found". Not sure what that means, perhaps the address I have for it is incorrect. But the one you gave will do.
     
  5. EricH

    EricH Eric Hamilton Moderator

    Location:
    Durham NC, USA
    Also the 1300 cars 75-78. The 74 had a dedicated air injection manifold with a port for each exhaust valve, Fiat cut over to the single drilled passage next year
     
  6. carl

    carl True Classic

    Location:
    Virginia
    OK, thanks. This is what I thought.

    At this point in most X's lives there have been so many changes and swaps that all kinds are mismatches can be in play.
     
  7. Dan Sarandrea (Phila)

    Dan Sarandrea (Phila) Waitin' On Parts...

    Location:
    Philadelphia, PA
    Looking at the gasket mating surfaces for the stat housing on the cyl head, we can see some significant erosion from corrosion. A good solution would be to clean the corroded areas thoroughly (bead blasting would be ideal as it gets in the nooks and crannies and leaves a nice textured surface for good grip), then apply a suitable metal-filled higher temp epoxy to fill the low spots, then sand smooth with a rigid and flat backer to your sandpaper.

    I did the above procedure on the three main coolant hose nipples of the stat housing on my car, as it had the typical aluminum erosion where the original hoses mated to the nipple. It took some time and patience but IMO it was worth it to ensure a quality mating surface to head off potential leaks and continued erosion.

    BTW your pic of the end of the block and head is very useful to illustrate where FIAT stamped the engine type and serial number.
     
  8. ecohen2

    ecohen2 True Classic

    Location:
    Arlington Va
    Do this.. Line up the two gaskets against each other and then look through the hole with the old one facing you. If you can see any of the new gasket then I would either trim it or get another gasket. I am curious for myself as well.. If the mechanic that did mine used the wrong gasket it would explain the white fluffy bits I see in my coolant... sigh...
     
  9. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    In Carl's case there is no corresponding hole in the block. So it will not matter if the (blind) hole in the T-stat housing is covered or not. The water cannot go anywhere harmful, it is just like having the other cover in place.


    If your block is the type with the hole in it (passageway behind the T-stat housing), and the wrong gasket is used, typically water will trickly out of the exhaust pipe. The passage leads to the exhaust ports, not the oil pan. So usually you will not see signs of oil/water mix (if that is what you meant). However I suppose eventually enough water could trickle into the exhaust ports and slowly leak past the rings? I don't recall if that has happened to anyone?
     
  10. ecohen2

    ecohen2 True Classic

    Location:
    Arlington Va
    Actually I was talking about the main hole where the coolant passes through. I am guessing that you have had a large flap of gasket material blocking part of the flow it would eventually break down and show up in the reservoir tank..
     
  11. carl

    carl True Classic

    Location:
    Virginia
    I looked at the head that was on the race motor and that this thermostat housing and four hole gasket was attached to and that head was indeed the 75-80 type with the air injection port. As discussed above, the head I'm using now is an FI head and does not have that port and either gasket would work fine. I'm using the FI gasket as shown new above.

    Dan, when I saw the picture of the end of the head I realized someone was going to comment on the corrosion. In fact, it's a trick of the picture and the "corrosion" is pretty much non-existent as anything more than a stain on the aluminum.
     
    Dan Sarandrea (Phila) likes this.
  12. Dan Sarandrea (Phila)

    Dan Sarandrea (Phila) Waitin' On Parts...

    Location:
    Philadelphia, PA
    So in a manner of speaking, it's an optical "delusion." LOL
     
  13. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Ahhh, my mistake. Sorry I misread your comment the first time.
     

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