Belsinor
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No I have a flamethrower 1.5ohm coil. I'll try .035 and see if that works
Front cylinders not firing when cold
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Belsinor
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I do not know for sure, when I bought the car I was told it was hydraulic but I confirmed with a scope that they are rollers. I have not done a compression test yet, but since they were firing when warm that was not high on my list to do. I'm trying to answer what I know and making a list of what to check next time I'm working on the car.
My last attempt was to take the carb off, remove the idle screws and blast air though to check for obstructions and fuel flow.
PRHeads
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Test the compression on a couple of front cylinders when the engine is cold.
Rishi
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If you have misfiring on cylinders #1-4 only, and ever only on #1-4, and all the while #5-8 seem to be firing fine?
That is an odd problem, for sure. But there are a few things I think we can rule out.
engine mechanical - I can think of nothing in the engine, valves, heads, timing, etc. that would cause only #1-4 to misfire while the engine is cold or hot, but then run fine when temperatures change.
fuel delivery - since there are "firing" and "non-firing" cylinders sharing the same carburetor (primary throttle) ports, and the same air/fuel mixture, we can conclude the fuel tank, fuel quality, fuel pump and fuel systems are all fine and working.
The only category I think remains is ignition involving the distributor, plugs and wires.
I had a mysterious problem on a 1968 New Yorker that took months to figure out. I happen to observe the engine running in the darkness of night, and noticed several places where my spark plug wires were leaking and arcing to ground.
Add to your long list of things to try: try and observe this misfiring engine in the total dark, to see if there are any visible signs of spark plug wires arcing or having issue.
That is an odd problem, for sure. But there are a few things I think we can rule out.
engine mechanical - I can think of nothing in the engine, valves, heads, timing, etc. that would cause only #1-4 to misfire while the engine is cold or hot, but then run fine when temperatures change.
fuel delivery - since there are "firing" and "non-firing" cylinders sharing the same carburetor (primary throttle) ports, and the same air/fuel mixture, we can conclude the fuel tank, fuel quality, fuel pump and fuel systems are all fine and working.
The only category I think remains is ignition involving the distributor, plugs and wires.
I had a mysterious problem on a 1968 New Yorker that took months to figure out. I happen to observe the engine running in the darkness of night, and noticed several places where my spark plug wires were leaking and arcing to ground.
Add to your long list of things to try: try and observe this misfiring engine in the total dark, to see if there are any visible signs of spark plug wires arcing or having issue.
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Refrigerator unplugged? 
OneWheelPeel
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I had a similar issue on the rear cylinders on a small block Chevy last summer, wasn’t so much temp related as rpm related tho. At idle the cylinders were dead, culprit was a carb spacer that was hacked on enough to disturb flow at lower rpms. 1 in a million screw up on my part but mentioning just in case.
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Sometimes engines are like women......you need to take the time to warm them up a little b4 using......????
BOB RENTON
Belsinor
Member
I have NGK #5 right now, going to try closing the gap to .035 and see if that helps
The front 4 cylinders are not in sequentitial firing order. To me that likely rules out coil, distributor, rotor, and wiring. And most likely the pick-up coil and cap as well. Also be pretty tough to have a vacuum leak at the maniold/head junction on those 4 cyinders only. That to me points to either a carb/intake leak at the front. Or an issue with the primary side of the carb internally. I'd try another carb. Don't have one? Take it off and install it backwards. See if the problem goes to the rear cylinders?
Doug
Doug
Belsinor
Member
I think I have an idea how you know, lol. Closing the gap to .035 brought 1 and 3 to life, if I bypass the resistor all 8 fire now
PurpleBeeper
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Excellent! I tried to gap .040” on a stock coil and my car wouldn’t fire. Maybe your coil is about to go out?
RemCharger
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A larger plug gap does nothing for power.
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Neither does any of the "wonder coils" that are said to provide 50+ blazing horsepower increases. 001" differrnce in plug gap make no difference . Try different gap configurations....side gap, j-gap, multi ground, surface gap. Try different brands.....besides what the narrow thinking NGK boys recommend.....you might be surprised. In my GTX, I use Champion HO-8A a platinum electrode non projected center electrode plugs origionally made for Homelite 2 cycle racing go cart engines running methanol and nitro methane mix plus castor oil......experiment a little.....
BOB RENTON
Bee1971
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What should I gap my spark plugs at?
From the article
Your ignition system may have lots of Voltage, but no Amperage. This is why even on high energy ignition systems, (CONTRARY to what their lame instructions say to gap your plugs at), you CLOSE the gap on engines making more power. Usually .035" is around the best gap, even though many instruction manuals say to open your gap to .045". Go ahead and try that, but when it doesn't run as good, or it drops cylinders at high RPM because that wider / weaker spark can't light the cylinders consistently, you'll know why. This gets even more true when you are running too rich and have too wet of a mixture. It's harder to light a fire in the rain than it is on a dry summer day. Inside your cylinder isn't much different.
On mild engines, (even you guys who have 400 - 550 HP), that isn't enough power to be concerned with on the gaps, and a gap of .045" will "probably" run just fine because you aren't burning enough fuel (a wet enough mixture) to cause cylinders to drop with a decent ignition system, but start getting over 600, 800, 1,000 horsepower and that .045" or so gap isn't going to work out too well. Either way, your milder engine WILL run better with .035" gaps instead of the .045" gaps that they tell you to run.
From the article
Your ignition system may have lots of Voltage, but no Amperage. This is why even on high energy ignition systems, (CONTRARY to what their lame instructions say to gap your plugs at), you CLOSE the gap on engines making more power. Usually .035" is around the best gap, even though many instruction manuals say to open your gap to .045". Go ahead and try that, but when it doesn't run as good, or it drops cylinders at high RPM because that wider / weaker spark can't light the cylinders consistently, you'll know why. This gets even more true when you are running too rich and have too wet of a mixture. It's harder to light a fire in the rain than it is on a dry summer day. Inside your cylinder isn't much different.
On mild engines, (even you guys who have 400 - 550 HP), that isn't enough power to be concerned with on the gaps, and a gap of .045" will "probably" run just fine because you aren't burning enough fuel (a wet enough mixture) to cause cylinders to drop with a decent ignition system, but start getting over 600, 800, 1,000 horsepower and that .045" or so gap isn't going to work out too well. Either way, your milder engine WILL run better with .035" gaps instead of the .045" gaps that they tell you to run.
Sportfury70
Member
Maybe a fuel delivery issue, possible leak at the front intake gasket. While it’s running rough at start up, try using a small propane torch (unlit of course) around the front intake runners where they meet the head and see if it smooths out. Engine might expand when warm enough to seal the leak.
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The Champion HO-8A (or alternately Champion UJ-11G) has a very broad heat range tolerance that resists low temp/low speed fouling (booster gap design) yet is immune to high speed/rpm pre-ignition conditions and due to the small diameter platinum center electrode resistant to mis fire and J-gap to allow better flame propagation. Name the NGK equivalent and I'll try them. Thus endith the lesson in proper spark plug selection........and put your preconceptions and hearsay knowledge in the round file.......
BOB RENTON
#1 - I would put a KV meter on plug wires @ plug end - sounds like weak spark, fuel is soaking plug until it gets heat to help #2 determine if wires or plug is issue as stated earlier, check gap - move a wire to see if issue moves with it - if your box & dist ( reluctor - cap - rotor , all of it ) are working ? You have to start @ the plugs and wires ! You can get a hand held spark tester KV tool and "walk" down the wires and determine what type of fire power you have getting to each cylinder very quickly - i use mine 1st tool i grab when they tell me there's a miss somewhere, need to be sure all are "close" , similar to a compression test but on the ignition side of the situation - best hunting to you
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