More sparkplugology

More sparkplugology

Paul
Paul

February 3rd, 2015, 9:07 pm #1

From the archives, more on spark plug reading to understand how your motor is tuned (and performing).







Always something we need to do at least once per season to SEE how things are running.
Sometimes if you can't tell by running the motor, you may be able to see something that is in need of an adjustment before damage or poor running comes into play.

I have seen articles saying the Motorcraft (Ford) plugs acually provide a marginally higher horsepower rating, but even if you ran the same dyno test on the exact same equipment you would get a marginally small delta in the data.

regards,

Paul
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Joined: January 28th, 2008, 7:59 pm

February 3rd, 2015, 11:05 pm #2

Not sure if there is an iridium plug I could use in my 307s. I think I could also use a slightly wider gap than stock because I have the pertronix conversion and 50k volt coils.
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Paul
Paul

February 4th, 2015, 2:13 pm #3

One thing about the higher voltage, more is better unless there is a weak link in the system and that could be wires or the cap, both of which could undergo deterioration faster with higher voltage. In any case that is my impression now and I stand to be corrected by anyone who knows more about the subject. I think the old style crab caps have a limit to which they function well. I don't want to start a bad thread on this so I would appreciate anyone stepping up with more info.

I will also check some other sources.

Regards,

Paul
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Joined: July 15th, 2005, 8:09 pm

December 15th, 2017, 2:47 pm #4


With old school points or the magnetic pick-up of Petronix, all the voltage still goes through the rotor and onto those cap electrodes. Higher voltage coils with caps that can't handle the voltage will just eat them up faster.









Regards,

Paul






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Paul
Paul

December 18th, 2017, 8:45 pm #5

I am due to some in-the-bilge quality time this winter when it is tolerable weather to twist a wrench. The sea water pumps are a *itch to get to, like wrestling a python in the bilge. They are mounted low at the front of a 427 where you have to be a contortionist to get to them. I aslo found a little spray coming from a circulation pump too, and that means I need to look closer and see if it's a gasket or something about the pump itself that will need attention. I'll chronicle all the work, but I'm not looking forward to it just now, it's cold out there.

When I get in there I'll also be checking all the plugs and setting valve lash.

regards,
Paul
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Joined: March 27th, 2017, 8:01 pm

December 20th, 2017, 11:01 am #6

With old school points or the magnetic pick-up of Petronix, all the voltage still goes through the rotor and onto those cap electrodes. Higher voltage coils with caps that can't handle the voltage will just eat them up faster.









Regards,

Paul





Paul, I had an old Mallory Ignitor on my Lancer when I first bought her. Was trouble shooting some electrical gremlins when a thunderstorm moved in real fast, in my hurry to pick up tools and run for cover I left the ignition switch on. Returned the Next day and found the old Mallory ignitor was toast. I replaced it with a a Pertronix system including the 40,000 volt "Flame Thrower" coil. All is well,the engine starts within half a crank and runs like a bear. But the first season I replaced two "crab caps" within 80 hours of running time. I checked and adjusted timing a bit and so far no more problems, but the engine timing was only slightly out of spec. Do you think these older engines benefit that much from a high voltage coil? Those caps are pricey, and now I feel I always need to carry a spare. Does that much voltage raise issues with even high quality wires? And the less I remove the distributor cap to take a look the better....that hold down system is ridiculous.... hard to get the tiny little metal tabs aligned properly especially in a rocking boat.
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Paul
Paul

December 21st, 2017, 2:33 pm #7

I don’t know if the motors “need” 40,000 volts but with my experience with the 427 motors in particular, they like it a lot. I have gapped my plugs open from something like a standard (from memory) .027” to a .055” with the HEI style distributors and I don’t need a choke to start them. I just prime the carbs by pumping a few times after activating the electric fuel pumps, let the fuel atomize in the intake manifold a moment, and then they jump right to life. I have run the 427s for several seasons now with ZERO issues, whereas before with the crab caps and stock fully rebuilt distributors, and then with crab caps and Pertronix pick-ups I would be eating the terminals on the inside of the cap. There are some other issues going on too, besides the poor design and construction of those expensive caps: I think moisture migrates up the shaft and into the caps when the oil heats up, and this creates a film inside the cap where particles can stick to the inside wall. I think the higher voltage in those old caps just eats them up faster too, and I absolutely would not leave the dock without a spare.

It’s just a poor design in my humble opinion, and it’s the weak link on Chris-Craft motors. If your Lancer is an outdrive model it likely has the Q motor, in which case I would send the distributor in to Performance Distributors if you are contemplating one of their marine DUI units, to be sure they match it up perfectly (and of course check physical clearances too because these things are big). If your Lancer is an inboard it could have the Q motor listed in the Essential Guide or it could have the 350K motor too because we know people who have these even though the EG does not list them, and if that is the case it would take the generic shaft length for the SBC motor.

I’m not a big fan of the crab caps, I like the appearance, they are very cool looking but after buying a box load of them for a variety of motors in the past I just swapped out the entire distributor and the savings has just about paid for itself now because those caps were in the fifty dollar range last time I looked for a 427.

Personally, if I was going to keep the boat and use it a few years, I would invest in a better distributor if it would fit, and be done with all the drama. There are alternatives on the market for marine units but since I have first hand experience with (four) DUI units I can recommend them (if they will fit).

Regards,
Paul




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Joined: March 27th, 2017, 8:01 pm

December 21st, 2017, 8:00 pm #8

I would love to dump the crab caps, old Mallory Dist. and the coil. The D.U.I. system would be the answer for sure, but I don't think it fits the 350Q with the short shaft. There is very little room if I remember correctly....boat is in storage. Does any other company build a short shaft marine distributor that might squeeze in there? I'll do some snooping on the web.....but this is the most knowledgeable forum on 350q's on the planet.
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Joined: July 15th, 2005, 8:09 pm

December 22nd, 2017, 3:50 am #9

He will send you a DUI that has the proper shaft

Paul
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