Running on 4 cylinders

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John Martin

Well-Known Member
Joined
Aug 7, 2019
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Location
Gurnee IL
The car is a 1970 Dart Custom
225/904
+/- 112k miles on it

So I’ve been chasing the misfire my car has had since I bought it. Every thing I have done so far has helped, but it is now to the point where I think I have done all I can. The car seems to only run on 4 cylinders.

I pull the spark plug wires and there is no change on #1 and #6. This is very peculiar. I know they are both companion cylinders so it must be something they both have in common.
 
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needs more fuel on the idle circuit 1/6 farest from carb could have a vacuum leak .idle circuit clogged up ,try gapping those plugs at .050 wide and check for a change, also some used a hotter plug in those cylinders because of a lean problem I thing ny16 was the plug ,But this is where SLANT 6 DAN can help you if he's out there
 
needs more fuel on the idle circuit 1/6 farest from carb could have a vacuum leak .idle circuit clogged up ,try gapping those plugs at .050 wide and check for a change, also some used a hotter plug in those cylinders because of a lean problem I thing ny16 was the plug ,But this is where SLANT 6 DAN can help you if he's out there

If this thing ran any richer the way it is right now it would have had a Perkins diesel from the factory. It rolls coal as it is.
 
put a shop rag loosely on top of carb and if idle speeds up its lean also 1/6 run lean , what do the plugs look like
 
put a shop rag loosely on top of carb and if idle speeds up its lean also 1/6 run lean , what do the plugs look like

I guess that it dumping black smoke out the tail pipe doesn’t mean anything then?

The spark plugs are black and dry, all six.
 
I guess that it dumping black smoke out the tail pipe doesn’t mean anything then?

The spark plugs are black and dry, all six.
If all 6 plugs are black and dry, all 6 are firing.
Be best to fix the rich carb problem before doing any additional tuning.
Could be as simple as a stuck float.
 
Why does everybody always ignore the most important first step? Stop playin around wasting time and run a compression test. On all 6. That way, you don't waste anymore time playing guessing games if you have two dead cylinders. If they have compression, oh happy day, then it's somethin simple. If not, start yankin the head. Pretty simple.
 
Why does everybody always ignore the most important first step? Stop playin around wasting time and run a compression test. On all 6. That way, you don't waste anymore time playing guessing games if you have two dead cylinders. If they have compression, oh happy day, then it's somethin simple. If not, start yankin the head. Pretty simple.
Because people are to naïve to believe anything anybody else says, and want to do it their way[the hard way]!!!!!!
 
If all 6 plugs are black and dry, all 6 are firing.
Be best to fix the rich carb problem before doing any additional tuning.
Could be as simple as a stuck float.
It was a bad metering block. I swapped one in from a known good one that was on a car that got 24 mpg and the smoke cleared up, the stink went a way and it runs a lot smoother.
 
Why does everybody always ignore the most important first step? Stop playin around wasting time and run a compression test. On all 6. That way, you don't waste anymore time playing guessing games if you have two dead cylinders. If they have compression, oh happy day, then it's somethin simple. If not, start yankin the head. Pretty simple.

The head was redone on this car and it looked typical of a 112k or so car. Worn but nothing that was very bad.
 
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