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9 minutes ago, F&J said:

I think you posted earlier that the cylinder would not fire "at any speed".  And somebody here also said something like: ..if a vacuum leak could kill a cylinder at high rpm's, it would have to be a huge leak..and therefore the engine could not possibly idle.

 

Looking forward to what you do find on this car.  it's a tough one.

 

 

I'm not sure its a total dead hole..........I think he said a skip or something similar. Thats why I suggested pulling the push rods and putting it on a five gas........to be sure the hole is the offending one. It's going to be an interesting fix.........Matt.......get it fixed! A bunch of us are wondering what the problem is......😎

 

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1 hour ago, kgreen said:

I had a cracked spark plug in an engine once that tested great and looked great.  But once I got it into the head, the spark was able to find a short cut to ground and made the cylinder miss.

 

Which was something Matt tried back in Post #1

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Got to ask: You say that the #2 spark plug was dry, but you smell raw gas like it is being dumped into the exhaust?  And you think it is coming from # 2 ? If it's dry then #2 must be firing or not receiving any fuel air mixture to actually fire.

 

Is this Cadillac engine an externally balanced engine similar to a  Buick 401 nailhead? 

Any chance the flywheel is not installed properly and your getting an out of balance vibration and not an actual miss?

 

Good Luck

 

Bill

 

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13 hours ago, wmsue said:

Got to ask: You say that the #2 spark plug was dry, but you smell raw gas like it is being dumped into the exhaust?  And you think it is coming from # 2 ? If it's dry then #2 must be firing or not receiving any fuel air mixture to actually fire.

 

Is this Cadillac engine an externally balanced engine similar to a  Buick 401 nailhead? 

Any chance the flywheel is not installed properly and your getting an out of balance vibration and not an actual miss?

 

Good Luck

 

Bill

 


Bill.......somewhere in the thread he said he could smell gas out the tail pipe. That should eliminate an out of balance engine.

 

 

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  • 2 weeks later...

Matt.......looks like it is going to become a "command performance"!

 

 

Now all you have to get to do is make the car perform...........😇

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Matt,

Here is a dumb idea.

Hook your timing light up to #2 and see if it lights up.

I've done that to all 8 cylinders on the Buick, just to check the continuity from the distributer cap to ground, thru the plugs, when I made new wires.

 

Mike in Colorado

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8 hours ago, edinmass said:

Matt.........any progress with the car? Inquiring minds want to know! 

 

Glad you asked! We pulled the carbs and intake and found...nothing. No cracks in the manifold, no damaged gasket, no warped mating surfaces, no obvious sign of anything that would cause that problem. Nothing, nada, zero, zilch.


We double-checked to be sure the valves really were moving through a full range of motion, and with the intake off we could watch the pushrods and put a dial indicator on the lifters. The cam is healthy and the lobes are not flat. Pushrods are not bent or damaged and most of the stuff in there looks new (I didn't take any photos since Roman, my mechanic, was doing most of the work and he just works rather than taking pictures, which is the right way to be a mechanic).

 

Anyway, without finding anything wrong, we bought new top-end gaskets from Olson's and put it back together. Once it was reassembled, we started it and voila! It's running on all 8 cylinders. What did we cure? What changed? No clue. New gaskets curing a tiny, unseen vacuum leak? Removing the distributor and reinstalling it changed something? A ground path was somehow restored? I just don't know. 


It's not running quite as smoothly as I think a Cadillac should, so we're going to reset the timing, pull the carburetors down a little bit more thoroughly than we did, and install new plugs, points, condenser, coil, and wires. It drives well as-is, the Tri-Power comes online as it should, and there's decent power at all speeds, it's just not quite as silky smooth as I think it should be so we're going to try to put a polish on the tune. I bet most people wouldn't notice or care, but I think it needs to be better than it is. And there's a con-founded exhaust leak (all '50s-60s Cadillacs have exhaust leaks) that we're going to try to cure, too.

 

I wish I knew what was wrong and what we "fixed" to cure the problem. That's as maddening as the problem itself. I don't like not knowing what was fixed because it could happen again and leave us back at square one. Will it continue to run properly? I don't know. We're going to do a full tune-up to see if it smooths out and go from there. Then I plan to drive it a few hundred miles to make sure whatever "repair" we've done is permanent. 


Roman said this has been the most frustrating thing he has ever done, and I don't blame him. After all that time and effort, we still don't know what happened or how to fix it in the future. And I can't exactly bill the customer for all those hours if I can't point to what we did as being the solution. This was a big lose-lose-lose for everyone involved. 

 

Meh.

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I'm sure you checked, but was there no tell-tale discoloration on the old gaskets, and/or, mating surfaces to indicate an intake leak ? 

 

Frustrating yes, but at last some satisfaction that you made progress despite the remaining mystery.  Times like that I just caulk it up to my Guardian Angle has a sadistic sense of humor. 😉

 

Paul

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On 6/26/2020 at 9:57 PM, edinmass said:

If it was the cap......you could have used an oscilloscope to check for high KV’s..........another useful but seldom used tool. 

 

I have a scope and I would not part with for anything.  It is a great tool for this kind of stuff.  Fortunately it is portable and works on 12 volts so I am not tied to the wall plug.  For 6  volt cars, just hook it up to a 12 volt battery.  🙂

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I’ll claim victory, as my post on page one said vacuum leak........and to just pull it apart. I’m quite certain it wasn’t a ground issue. I hate fixing things and not prove something was wrong.......but it happens five percent of the time. Check the timing, and the advance curve......as well as fuel pressure.......always the basics. 👍

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15 hours ago, edinmass said:

but it happens five percent of the time.

 

I hear that !!

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Matt,

Congratulations on the "fix", what ever it was.

 

But I sure hate reading a long book, and having the last page not reach a climax / conclusion.

 

Not wishing it would come back though just to entertain the gang.

 

Happy motoring.

 

Mike in Colorado

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