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1950 buick - engine mis-firing


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Hello. On my 50 super the engine is missing when it warms up. The problem isn't electrical we've determined that. It also has an exhaust leak too. Last year I removed the valve body because it was frozen shut and got that all freed up. I took the carburator off and take exhaust manifold off and replaced their gaskets with new. Tightened all the bolts but I've noticed that the exhaust pipe doesn't fit 100 percent with the flange but the sound is mostly coming from the manifold. Thank you.

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Could have a crack or hole in the heat riser part of the manifold. The manifold in that area is designed to warm the intake up and will open up a crack and cause a miss. I've seen this before. Not uncommon. Dandy Dave! 

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Your exhaust leak can be cured with a nice fat Remflex manifold gasket.

 

Be careful...the manifold is quite heavy, especially when leaning over a fender!

 

My '39 Special manifold is so warped that I even needed a extra layer of the old gasket on one outlet.  Manifold side of the Remflex, not engine side.  I sealed that layer to the manifold with Permatex 81878 high temp silicone.

 

Working fine for a couple of years now.

 

Can't help with the misfire, though.

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  • Peter Gariepy changed the title to 1950 buick - engine missing
  • 4 weeks later...
  • Peter Gariepy changed the title to 1950 buick - engine mis-firing

Sure. The wires and plugs were installed shortly before I purchased it. The car had sat for many years before that. The coil was replaced by me because the previous owner used a jump pack to get the car going but ruined the coil in the process and it wouldn't start. The wires didn't arc across each other either. The carburator is having choke problems by itself. If you manually operate the choke at open and closed positions the miss is better.

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From what I have heard, today's oil filled coils are not as durable as the old epoxy filled ones.  @KAD36 has documented several coil failures within weeks of purchase on his 55.  So you may want to consider this possibility. 

 

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9 hours ago, JohnD1956 said:

From what I have heard, today's oil filled coils are not as durable as the old epoxy filled ones.  @KAD36 has documented several coil failures within weeks of purchase on his 55.  So you may want to consider this possibility. 

 

 

Went through 3 coils in 2 years.  Misfire at hot idle and no misfire at cold or during warmup was early indicator.  Cars primary and secondary circuits all checked out ok.

 

The original delco coil was filled with a thick oil as are most today.   Maybe I just had a run of bad luck but an epoxy filled one mounted horizontal so far works fine.  It seems people are successful if a newer oil filled coil is mounted vertically. Or use an older made in USA one if mounted horizontal.
 

Cannot explain it, just sharing results of my research. I wasn’t comfortable running long distance with a 40 or 70 year old used coil as the primary ignition source and was tired of getting stuck..  Maybe carrying a box of old ones and playing swaptronics would be smarter lol.

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Another bit of failure info that may help - two of the failures the secondary resistance failed hardcover open.  The last failed at hot measuring well over 150 k ohms on the secondary and 8.5k ohms room temp (12 v system).  If your misfire is at hot only consider a secondary resistance check to see how well it holds spec at hot w everything disconnected at the coil, understanding resistance check is only a quick DIY indicator and not a comprehensive coil test.  Even with newer wires, the routing to ensure no induced crossfire between adjacent wires, integrity of primary wiring between coil and distributor and other “easy” things should be considered first.

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19 hours ago, Mr. Reed said:

Sure. The wires and plugs were installed shortly before I purchased it. The car had sat for many years before that. The coil was replaced by me because the previous owner used a jump pack to get the car going but ruined the coil in the process and it wouldn't start. The wires didn't arc across each other either. The carburator is having choke problems by itself. If you manually operate the choke at open and closed positions the miss is better.

 

 

If the electrical is up to snuff and you noticed it is less evident(misfire) when the choke is manually operated I would look in the manual for proper choke adjustment(cold start).  It is also possible the carb is dripping gas(un-atomized) when cold(possible vacuum leak).  Gas burns in atomized form.  Take a look down the throat of the carb at cold start.  Check to see if gas it dripping or visibly getting sucked into the venturi as drops of gas.             

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I was going to send the carb off for a rebuild and i purchased a set of metal spark plug wires separators in a kit from cars llc. They have thread holes in them but I'm not sure where they go. The spark plug cover is off and I want to put it back on with the wires separated.

4 hours ago, KAD36 said:

Another bit of failure info that may help - two of the failures the secondary resistance failed hardcover open.  The last failed at hot measuring well over 150 k ohms on the secondary and 8.5k ohms room temp (12 v system).  If your misfire is at hot only consider a secondary resistance check to see how well it holds spec at hot w everything disconnected at the coil, understanding resistance check is only a quick DIY indicator and not a comprehensive coil test.  Even with newer wires, the routing to ensure no induced crossfire between adjacent wires, integrity of primary wiring between coil and distributor and other “easy” things should be considered first.

 

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