Time to Remove the Cylinder Head ?

Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
 I am trying to resolve problem of the spark plugs sooting up on my 1934 254 engine.
Advice from Geoff and the ROC was to try hotter plugs so I replaced the 3/8"  B6S NGK plugs with 1/2"reach NGK plugs at the next heat range. Longer reach are OK in '34 and '35 engines with ridge running the length of the head.
However, when just turning the engine over on the starter something in cylinders 1 and 8 seems to have hit the plugs in them and has squashed their ground electrodes. The other plugs are OK.
This problem never occurred with the 3/8" plugs.
So I'm guessing the head needs to come off to find out what's going on here - could it be stuck valves or something else ?
Opinions/advice would be very much appreciated, please !

Comments

  • paulrhd29nzpaulrhd29nz Posts: 231Member
    are 1 & 8 the plugs that soot up on you when you had the 3/8” reach in ? 
  • Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
    are 1 & 8 the plugs that soot up on you when you had the 3/8” reach in ? 

    Yes, but so did all the others to varying degrees.
  • 35Terra35Terra Posts: 69Senior Contributor
    Just a thought here.  Could the other spark plug holes still have a metal gasket stuck on them from a previous plug. Thus keeping the plug from hitting anything since it would essentially have two gaskets? I know this would have no bearing on the fouling  of the plugs.
  • Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
    35Terra said:
    Just a thought here.  Could the other spark plug holes still have a metal gasket stuck on them from a previous plug. Thus keeping the plug from hitting anything since it would essentially have two gaskets? I know this would have no bearing on the fouling  of the plugs.
     I . I have just gone out to the garage and checked it out - but there are no plug washers stuck in any of the holes.

    Just checked that and no,that isn't the problem.
  • 50C8DAN50C8DAN Posts: 2,066Senior Contributor
    Could be that variable valve timing technology that Hudson pioneered in the 30s?   B)
  • supercubsupercub Posts: 118Member
    You could have a sticky float, worn valve guides or seals (if equipped) or low spark output causing the soot. You can use a vernier caliper at TDC for each piston to determine the piston clearance. A compression test will tell you if the valves are blowing by. Do you have any oil consumption?
  • GeoffGeoff Posts: 4,096Senior Contributor
    Obviously the plugs are being donged by the valves.  I had this in my previously owned Pacemaker, which had the wrong plugs in, which protruded down into the combustion chamber further.   the head had also been planed, which obviously exacerbated the problem.  I changed to champion J8 plugs and no further problems.   Change back to the J8's and  try lowering the float level in the carb, it is obviously running too rich.  If it is oil contamination then  that is a different kettle of fish.  Not sure if there is a J10 plug, or something else in a hotter range with short reach.   Perhaps you also need to check the spark intensity.   Are you using carbon h.t. leads or wire cored?  Is the coil polarity correct.   If reversed this reduces the spark intensity by 15%.   If you pay my fare to Britain I'll come over and fix it for you, but not until  you have been cleared of the plague!!!
  • Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
    Geoff said:
    Obviously the plugs are being donged by the valves.  I had this in my previously owned Pacemaker, which had the wrong plugs in, which protruded down into the combustion chamber further.   the head had also been planed, which obviously exacerbated the problem.  I changed to champion J8 plugs and no further problems.   Change back to the J8's and  try lowering the float level in the carb, it is obviously running too rich.  If it is oil contamination then  that is a different kettle of fish.  Not sure if there is a J10 plug, or something else in a hotter range with short reach.   Perhaps you also need to check the spark intensity.   Are you using carbon h.t. leads or wire cored?  Is the coil polarity correct.   If reversed this reduces the spark intensity by 15%.   If you pay my fare to Britain I'll come over and fix it for you, but not until  you have been cleared of the plague!!!
    A tempting offer, Geoff ! 🤣

    But why is it only happening with 2 plugs and not all 8 ?
  • Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
    Geoff said:
    Obviously the plugs are being donged by the valves.  I had this in my previously owned Pacemaker, which had the wrong plugs in, which protruded down into the combustion chamber further.   the head had also been planed, which obviously exacerbated the problem.  I changed to champion J8 plugs and no further problems.   Change back to the J8's and  try lowering the float level in the carb, it is obviously running too rich.  If it is oil contamination then  that is a different kettle of fish.  Not sure if there is a J10 plug, or something else in a hotter range with short reach.   Perhaps you also need to check the spark intensity.   Are you using carbon h.t. leads or wire cored?  Is the coil polarity correct.   If reversed this reduces the spark intensity by 15%.   If you pay my fare to Britain I'll come over and fix it for you, but not until  you have been cleared of the plague!!!
    A tempting offer, Geoff ! 🤣

    But why is it only happening with 2 plugs and not all 8 ?
    I have ordered a set of Champion RJ12C plugs that are 3/8" inch reach from The Green Spark Plug Company (a British supplier of ignition stuff for old cars).
    They said they are hotter than the Champion J8 and are their recommendation.
    I'm using copper wire leads.
    Core polarity is correct.
     I will drop the carb float by 1/8".

    However, my cylinder head should handle 1/2" reach plugs and it's worrying that when I use them, plugs 1 and 8 get squashed electrodes.
    Something must be wrong in those cylinders, so I guess I should still remove the head for an inspection ?
    I have a spare head gasket, so it's not going to be an expensive exercise.
  • 54coupe54coupe Posts: 614Member
    I would compare the valve lift between all the cylinders, through the spark plug holes. Could the offending valves in 1 and 8 have been replaced with valves with a thicker head? (and so they are closer to the head to start with? Are they adjusted properly? I'm thinking you can get to the bottom of this without removing the head. 
  • JACK356JACK356 Posts: 114Member
    1 AND 8 IGNITION   16258374
  • Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
    Well not much luck today.
     I am going to have to take the head off in any event because the plug hole for #7 has been helicoiled and the darned thing has come loose and I'll need a new one put in.
    😩😩😩

    On the bright side (I suppose), I'll find out what's damaging those plugs in cylinders 1 and 8.
  • GeoffGeoff Posts: 4,096Senior Contributor
    Most likely as mentioned, thicker valve heads.
  • GeoffGeoff Posts: 4,096Senior Contributor
    Incidentally  you don't need to remove the head to replace a helicoil.  Make sure the piston is on t.d.c. on the firing position.  Do the surgery and then blow the detritus  out with  compressed air.   However, I would be searching for a replacement head if I were you. 
  • Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
    It's easier said than done to find a replacement head in the UK, Geoff !
     I will take it off and get it examined by the engineer who'll do the helicoil.
    Fingers crossed it'll be OK.
  • bob wardbob ward Posts: 1,229Senior Contributor
    Absent a replacement 34/5 cylinder head should one be required, it is possible to use any of the later 8 cyl heads with a fabricated adapter to mount the water pump.
    The water pump adapter system has been used for many years, this is a modern example on a 35 engine.


  • Old Fogey UKOld Fogey UK Posts: 558Expert Adviser
    Thanks very much for the tip, Bob.
     I hope it doesn't come to that but if it does, I'll be back to you for more info.
Sign In or Register to comment.