340 Spark Plug Wiring Schematic

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Big Guy

Big Guy

1970 Dodge Dart Swinger
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Nov 2, 2022
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Winnipeg, Manitoba, Canada
I wanted to replace the spark plug wires on my 1970 340 Swinger that I recently purchased with little history. I found that 3 of the wires were too short from a Mopar OEM set for 340 engine. Upon further investigating and research I have found part of the problem but the remaining part has me baffled! Seems that the #1 piston - the one on drivers side closest to fan - is connected to the distributor at the 12:00 position. All diagrams that I have seen and comparing to my neighbors 69 340 Swinger, that the #1 piston should be connected to the distributor at the 6:00 position. Car runs fine this way but how is that possible? Is the timing chain installed incorrectly or how can it be fixed or just leave it alone?I have attached a photo of my incorrect schematic for you to review.

Big Guy's 340 Spark plug wiring .jpg
 
Sorry I thought you were referring to the prev owner. TC =timing chain.....ok so maybe not dot to dot, but the dist was put on "180* out" which would put rotor pointing to rear of cap instead of front??
Big Guy said:
When you refer to “he”, are you referring to the previous owner? Excuse my ignorance but what is TC set?
Click to expand...
 
Did not think that the motor would even run if that was done?? Seems to run great! Solution is to just install distributor properly and read adjust timing?
 
Subscribed!!! Inquiring minds want to know...

I just can't figure out how that is even possible! Cam 180 degrees out???
 
4spdragtop said:
ok so maybe not dot to dot, but the dist was put on "180* out" which would put rotor pointing to rear of cap instead of front
Click to expand...
There you go!

Timing chain is supposed to be dot to dot

Screenshot_20230123-220801.png


To the OP....

you can leave it the way it is (just confusing down the road) or lift the dist up a half inch or so, rotate the rotor 1/2 way around and set the dist back in.

Reset the spark plug wires to correct.

Set timing, and drive on.
 
Jesus Christ guys COME ON. Has nothing to do with the timing sprockets. If they are in time the engine will run. "Dot to dot" at 12 and 6 O' clock becomes "12 and 12 O'clock" in the next 1 revolution of the crank, and goes from no 6 firing to no1 firing

OP THE REASON THAT your no1 wire is not where the book says is either

A.....because the drive gear is not installed by the book or
B.....You happen to have a distributor that the drive tang is not aligned with the rotor as other distributors are or
C....The dist shaft/ rotor is installed "180 out" and the no1 wire is where the no 6 would have been if it was the other way around. These distributors only install every 1/2 turn as the drive is like a screwdriver

IF YOU NEED or desire to fix this, Go to MyMopar and download a free service manual for the year car or close to it. You may have to settle for Dodge/ vs Plymouth.

The dist gear is supposed to be installed such that with the timing marks on TDC, the drive gear slot is pointing at the front left (driver side) intake manifold bolt hole
 
Big Guy said:
1. Seems that the #1 piston - the one on drivers side closest to fan - is connected to the distributor at the 12:00 position. All diagrams that I have seen and comparing to my neighbors 69 340 Swinger, that the #1 piston should be connected to the distributor at the 6:00 position.

2. Car runs fine this way but how is that possible?
Click to expand...

Number one: The distributor is in 180 from where it should be, take it out and spin the shaft along with the rotor.

Number two: The wires were put on correctly for the rotor pointing the opposite from where it should be.

This has NOTHING to do with the timing chain, lets get this thread back on track.


Alan
 
The distributor is installed 180 degrees out. Like recomended above, simply and easily pop it out and put it back I. So the rotor points forward instead of back towards the rear of the car.
 
I know what I meant by "180 out", hoping the OP does as well.
Bring up to #1 tdc. Pull cap, rotor, distributor and all the wires and start again by pointing rotor to front of engine.
 
Or, to say the same thing another way.

Get the rotor pointing towards your number 1. Pull the distributor and rotate rotor to point to your number 6. This now becomes #1. Pull all wires and connect to 18436572 firing order.
 
FYI, To give myself peace of mind, I finally got to work on my distributor being 180deg out. I fixed the problem by simply removing the position locking bolt, lifting the distributor, rotating the rotor 180deg, dropped the distributor back down and tightened the 1/2" bolt to hold in position. I then re-installed wires following the proper schematic with the #1 towards fan rather than at the fire wall and all is good! The motor fired right up and is running great! Simple fix!
 
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