Correct plugs for electronic ign.? 273 auto

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rebrabtrebor

rebrabtrebor

Aussie A body AP6 1966 V8
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hi, looking for an answer! Running a 273 1966 Valiant, but have a miss fire under load. Electronic ignition was fitted prior to my ownership, but seems to be installed well. can anyone point me in the direction of correct part number for spark plugs? NGK preferred! I have changed Dizzy cap, arm, leads, plugs (same as what came out) etc but it has had NO affect at all.

Also thinking it might not be ignition at all! may be fuelling problem from old 2bbl carb, but want to check the obvious first... :burnout:

thanks peeps.
 
The plug I use for my 318 is the NGK GR4, part # NGK 2635, its a v-power resister plug easy to read, I like it best, just my preference..........good luck
 
First, set the timing, drive, then read a plug; for carb. What is the fuel pressure? etc
 
Plugs don't need to be any different for electronic ignition.

You can do some simple tests to see what's going on

Google and learn how to use a leakdown tester, and you can make 'em yourself

Get and use a vacuum gauge

You can also do a "backyard" cylinder balance test.

Inspect the cap and rotor for damage, cracks, carbon, arcing, etc

Use your multimeter to measure the spark plug wires for opens

Remove and inspect the plugs. Check for obvious signs of failure or fouling, cracks in the plugs insulators. What color are they? what is in there now? What shape do you THINK the engine is in, does it normally put out good power, run good, smoke/ burn oil?

Then do your "balance test."


Make arrangements to short each plug tower individually. If you have the older, conventional style dist. cap, and a long sharp probe such as a 12V test lamp, you can use that, just ease it down beside the plug wires after moving the caps up the wires.

Alternatively, you can stuff small brads/ nails down beside each wire, so you can short them

Get it running and warm, adjust for best idle, and turn the idle up around 1200. Short each plug wire one at a time, and listen to the engine or watch a tach, each cylinder should drop the same RPM.

If not, swap plug or wire on that cylinder to check for a bad plug or wire.

If that does not change the problem, take a good look at that one (or two) cylinder(s), compression check, valve adjustment, etc.
 
RangerRick said:
The plug I use for my 318 is the NGK GR4, part # NGK 2635, its a v-power resister plug easy to read, I like it best, just my preference..........good luck
Click to expand...

NGK's seem to have the best Idle quality for any plug that I've run. Autolites seemed to be the worst.

I use NGK's GR5 in my 273 with the dual point distributor. I had tried an HEI conversion, but didnt seem to see the power difference other folks had seen, so went back to the dual point.

The GR4's were too hot for my compression ratio. GR4's seemed to do well on a lower compression 318 I was running for awhile. But went back to the GR5's after I got the 273 running again.
 
change your distributor cap and new plug wires if they are old .... cheap maintenance that can fix a myriad of misfire problems
 
check the polarity of the coil. If the wires are reversed it will cause a voltage loss that is shown as an engine miss.
 
deadly dart said:
check the polarity of the coil. If the wires are reversed it will cause a voltage loss that is shown as an engine miss.
Click to expand...

ahhhh, i did put a new coil on, it could be incorrect. :? another option first before carb strip down then.
:newb:
 
67Dart273 said:
Plugs don't need to be any different for electronic ignition.

You can do some simple tests to see what's going on

etc.
Click to expand...

ok, things i have done so far -changed all plugs, leads, cap, arm and coil (which i will now double check for suitability) i have checked i have a good spark with all 8 plugs, and i am happy (now) with the application of NGK bpr6es plugs. I have compression tested all cylinders as written in the Chilton hand book! she purrrrrrs on tick over and revs freely standing still, but put her in drive and go down the road she misfires like a bride after a hen night and sounds as bad as one too! she struggles to get over 50mph and i have seen this car pass me doing 100mph happily before the previous owner 'tinkered' with the ignition. the electronic ign seems (?) to be fitted ok, but i have no reference to its fitting, only that as stated above she purrrs. The coil was pointed out as an option and i will double check that this weekend, if not i guess the next step is under fueling from the old 2bbl carb, so a strip down is due, should be fun, haven't done that in 20 years! :!
 
Before changing the coil, check you fuel pressure, after that, you might want to open the gap on your plugs to about 55 or 60 thou. Most electronic systems need a wider gap on the plugs, otherwise it will eat the tangs off the plugs. Just a few suggestions. hope they help.

Bill S.
 
make sure your ballast resistor is connected properly. if it is not ,you will have a misfire under load and a very weak spark at the cap.
 

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rebrabtrebor said:
.... she struggles to get over 50mph and i have seen this car pass me doing 100mph happily before the previous owner 'tinkered' with the ignition. the electronic ign seems (?) to be fitted ok, but i have no reference to its fitting, only that as stated above she purrrs...
Click to expand...

Misfiring usually an indicator on timing.

First, probably doublecheck the firing order to the cap wiring. Could have swapped 1 or 2 wires accidentally. I've done that before.

Second, doublecheck the rotor to make sure that the electrode isnt loose. I had a brand new niehoff POS come apart within 15 hours of use. I was on the car's first run down the race track and the rotor came apart about 1/2 way down the track.

Hows your vacuum advance on your distributor??


Now to the other extreme.
I had a hellofatime with my ramcharger a few years back. Was out toole-ing in the desert and on the highway heading back home it started backfiring any faster than 40mph. Went thru everything. Ignition, Timing, Plugs, Wires, Coil, Distributor, etc. Could get it to run and move, but not very drivable. Was doing an oil change not long after and found metal in the bottom of the oil pan. After investigating, It ended up being a wiped #8 exhaust lobe on the cam. I hope your's isnt at this extreme.
 
a massive thank you guys, I have plenty to do this weekend now (gets me out of painting the house!)
@ 73, thanks for the diagram, i have no instructions etc for ignition system currently fitted so anything helps.
@ Chewy (i hope thats star wars related?) i pray its not as bad as that :/ and i will check the above.
@ Bill, would a knackered old fuel pump, say 46 years old cause that? maybe upgrade to electric fuel pump.... can get a 3bar pump, that should sort pressure problem.
 
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