Register now to get rid of these ads!

Technical 346 Flatty Performance question

Discussion in 'The Hokey Ass Message Board' started by 54caddycoupe, Apr 14, 2020.

  1. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Howdy from Texas, The head gasket on my original 346 Flatty (48 Cad Club Coupe) is apparently allowing oil to be sucked into the pistons causing smoke and hard starting. My question is ..since I am going to pull the heads to replace the gaskets .. what else could I do while I am in there as general maintenance and/or performance upgrades ? I have seen some pics from fiftyV8 that show the lefthand crossover exhaust had been removed to create a true dual exhaust ? Any other maintenance /performance suggestions appreciated. Thanks
     
  2. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Yes, I am back from the shop .
     
  3. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,832

    Mike51Merc
    Member

    I don't know about Cadillac flatheads, but Ford flatheads have no oil in the heads and no way for a head gasket to allow oil into the combustion chambers. How are Cads different?
     
    Register now to get rid of these ads!

  4. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Well, I honestly dont know. I am getting oil in my cylinders causing smoke. I also am getting oil and water thru the blow by tube but there is no water in the oil .. The dip stick is clean of the classic white sludge associated with a blown head gasket. I assumed that the gasket had failed next to the piston and valves allowing the oil to be sucked into the cylinder rather then failing between the oil and water jacket allowing coolant into the oil. I could be wrong.. I had one middle head bolt on the left side leaking oil. I tightened it to 70-75 ft lb's. But I feel the damage has already been done. I want to add that this is my First Fathead .. So my diagnostic skills are very limited since I have always had 1952 and newer Caddies.
     
    Last edited: Apr 14, 2020
  5. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,832

    Mike51Merc
    Member

    OK, so I think you first need to figure out whether there are oil passages in the heads. There probably are none, because there's nothing to use oil up there. The oil has to be passing through the rings to get into the combustion chambers, which also means your head gaskets aren't the problem, but regretfully you may have a bigger problem.

    Water in the blow by tube may be condensation from the crankcase. Or if coolant is leaking into the cylinders from the head gasket, you'd have steam (looks like smoke) coming out the exhaust. One way to check for coolant leaks is to drain the oil and see what comes out first (coolant sinks to the bottom of the oil pan).
     
    Nailhead Jason and squirrel like this.
  6. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Okay, Thanks for your help. I will check it out and let you know what I find.
     
  7. squirrel
    Joined: Sep 23, 2004
    Posts: 46,362

    squirrel
    Member

    yup, sounds like a ring problem. You might want to do a compression test, it's the first step in diagnosing engine problems.
     
    Desoto291Hemi and 54caddycoupe like this.
  8. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,832

    Mike51Merc
    Member

    Just another thought, worn out valve guides may allow some oil to be sucked in on the intake side, but I don't think it would be much because it would have to defy gravity.
     
    54caddycoupe likes this.
  9. When I bought my Flathead,,,,#1 intake valve had lost its horseshoe off the valve guide.
    Looked like it had been that way for a while ,,,the guide was worn very bad from bouncing up and down . It also had drawn oil into the chamber ,,,from the vacuum created by the piston,,,,entire chamber and valves were coated with oil from the tappet chamber .

    I was gonna post earlier,,,but I wasn’t sure about a Cadillac Flathead .
    I didn’t think they had any oil above the head,,,,,but,,,,I only have a little experience with a Mercury,,,,,I didn’t want to speak out of turn .

    It sounds like the caddy is using oil ,,,,,or ,,,it is leaking antifreeze into the chamber .
    I can’t imagine oil leaking from a head bolt,,,,it must be something else .

    Tommy
     
    54caddycoupe likes this.
  10. What year Cadillac is this,,,,,my Motors manual shows overhead valves from 1949 up .

    Tommy
     
  11. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,832

    Mike51Merc
    Member

    The man said 48.
     
  12. Forgive me,,,,,I was looking at his avatar .

    Tommy
     
    54caddycoupe likes this.
  13. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Yes, it is a 48 Flat head (346) there is a row of head bolts down the middle of the head. The 2nd one from the front on the left side was leaking oil.
     
    Desoto291Hemi likes this.
  14. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,072

    fiftyv8
    Member
    from CO & WA

    I am a little late to this party and it seems most thoughts have been aired.
    I am not sure that I can add anything right now except to say, be sure not to over fill your engine oil level as that could possibly force oil vapour to be pressurised, but not sure where it would come out without seeing detail engine pic's to know what has been done to your engine.
    IMHO going back to your original question regarding improvements. probably consider improving spark (HEI dizzy), exhaust out (twin pipes) and fuel in (multi carbs).
    No different to dealing with any other mild engine improvements.
    Other improver is to lose engine weight I guess.
    Generator to alternator and mini starter motor for starters pardon the pun...
     
    Texas Webb and 54caddycoupe like this.
  15. squirrel
    Joined: Sep 23, 2004
    Posts: 46,362

    squirrel
    Member

    Dual exhaust on one of these is a bit more challenging that most engines, since the exhaust comes out the top of the engine.

    I wouldn't get too carried away with trying to modify stuff, until you have good understanding of how it works as designed, and you can get it to work as designed. Don't get too far ahead of yourself.


    IMG_20180922_125812.jpg
     
    Desoto291Hemi and 54caddycoupe like this.
  16. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Thanks Russ. Great advice. Enjoyed the video's
     
  17. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Thanks , I will get her running right ,, then modify ..
     
  18. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,072

    fiftyv8
    Member
    from CO & WA

    Simplest exhaust is like this, but still will require some effort.
     

    Attached Files:

  19. squirrel
    Joined: Sep 23, 2004
    Posts: 46,362

    squirrel
    Member

    Lots of heat near the carb(s) with these engines....
     
    54caddycoupe likes this.
  20. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    The exhaust I saw and thought would be doable was on a 346 that used the factory left side exhaust manifold exit port and eliminated the crossover from the right side and ran the right exhaust pipe from the crossover port on the right side manifold.
     
  21. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,072

    fiftyv8
    Member
    from CO & WA

    Most things can be achieved with time, money, skill and motivation.
    Compression test would be a good first start point.
    Decisions from then on can be based on the results you get...
     
  22. 54caddycoupe
    Joined: Oct 11, 2011
    Posts: 23

    54caddycoupe
    Member

    Thanks Russ , I will let Yall know what I find .
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2020 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.