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Topic: Spark Plugs for Big Block?

in Forum: C3 Engines


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Spark Plugs for Big Block? (3/13)
 9/5/09 6:16pm
Gunslinger
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Frederick, MD - USA

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1969 convertible L71 427/435 4-speed black interior


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Don't go with expensive plugs like Split-Fire.  I tried them once and two of them cracked their ceramics within a very short time.  After I installed standard Champions (this was a big block Mopar, not a Vette), I had no more troubles.

Unless you've done some high performance modifications to the engine or to address a specific problem, I can't see where you need anything beyond an original equipment or equivalent brand spark plug.  Just get the proper heat range.  All exotic spark plugs do is lighten your wallet and add nothing to your engine's performance.  If the car manufacturer calls for an exotic plug, use that...if the car manufacturer calls for a standard grade plug...use that.  Of course most have their favorite brands...just like motor oil, car wax, etc.

That being said, AC Rapid Fire plugs are excellent.  They're different from Split Fire.  The tip design is supposed to last linger without eroding like a standard tip...true or not I can't say, but I use them in my 427/435 and so far they've worked well.
Spark Plugs for Big Block? (4/13)
 9/5/09 9:15pm
bio11
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Oklahoma City, OK - USA

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I had a set of 44T plugs in it when I first started it. I switched to the 43T after seeing that they where recommended in one of my Manuel's. I think it idled better with the 44's, but it's hard to tell. My #6 cylinder seams to want to foul a little. That plug looks a little oily. The others look fine. Maybe a set of the rapid fires would help a little.
Spark Plugs for Big Block? (5/13)
 9/5/09 9:44pm
anips
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sonoma, CA - USA

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if your motor is original and not rebuilt and has some miles on it then problem with# six might be the valve seals being dried up or torn, you can replace them without pulling the head, but its a project if you do one you should do em all, a good winter job, if # 6 bugs you do do a compression and leak down test on that cylinder.
Spark Plugs for Big Block? (6/13)
 9/5/09 10:26pm
bio11
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I checked compression about a week ago, all cylinders are at or within 1 or 2 lbs of 150lbs. So could be the valve seals. I should have done the leak down at the same time. What about plug gap...right now I gap them at 32...but i see some use 35. Would this help with fouling?
Spark Plugs for Big Block? (7/13)
 9/6/09 10:24am
anips
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35 is standard for a point type ign. the smaller the gap the smaller the spark, the comp. looks good, think about maybe a hotter ign., Pertronic, HEI, MSD, where you can open the plug gap up to as much as 50 or more for now?anips2009-09-06 07:27:55
Spark Plugs for Big Block? (8/13)
 9/6/09 11:13am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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If it runs/idles better with the hotter 44s in it, that's what you should use. The slightly colder 43s might be allowing the #6 cyl. to load up. You may indeed have a bad valve seal on that cylinder. The hotter plug will keep the oil from fouling the plug like the 43 is doing.
I've always gapped my point-type Chebby plugs at a tight .30"...just too old school to change.
 A hotter ignition system would allow a wider gap, which helps greatly to increase the spark across the electrodes.
Definitely change all of the valve seals if you decide to do it. Lots of folks only put the seals on the exhaust valves, but I prefer to put them on both intake and exhaust. I also only use the "umbrella" type seals...not the goofy little o-ring types...those are pretty much useless, imho.


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Spark Plugs for Big Block? (9/13)
 9/6/09 12:30pm
bio11
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Oklahoma City, OK - USA

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Messing around with it this morning....I had a set of 44t's in the cabinet, so i put those in and increased my idle from 600 up to 700. Drove it 5 or 6 miles...stopped a few times to let it idle a while to see if it was going to try and drop that cylinder and it never did. Got back to the house and tried to idle it back down some but it tried to miss a little so set idle back up to 700. I'll see what happens the next day or so. I'll try to put a few miles on it and see how it does and also keep an eye on oil consumption. Joel would the smaller gap help this problem?
Spark Plugs for Big Block? (10/13)
 9/6/09 3:57pm
anips
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another problem is with the stock stamped rocker arms is when the valve opens the rocker it pulls the valve stem  against the valve guide and eggs out the guide causeing more stem to guide clearance allowing more oil  to run down the guide, worn intake guides and seals cause oil consumsion, because the incoming air charge pulls the oil into the combustion chamber through the guide.
Spark Plugs for Big Block? (11/13)
 9/6/09 8:05pm
Adams' AppleLifetime Member
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Joe(anips) is right aboot the rocker arms pulling the valve off-center, especially on older, higher mileage engines...just the nature of the beast with regular rocker arms, tho...
Closing the plug gap up will not help with the oil fouling...it will most likely make it worse. If you close the gap a bit, and it seems to run better, then you prolly have a bad plug wire, or dist. cap terminal for that cylinder. The compression readings are fine, but a leak-down might point to rings that aren't sealing well in a particular cylinder...


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Spark Plugs for Big Block? (12/13)
 9/7/09 4:39pm
bio11
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Oklahoma City, OK - USA

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I put about 120 miles on this thing today...no problem with missing or anything, I think I'll leave everything set where it is for now. I'll keep my eye on oil consumption and probably when the weather gets bad I'll put some new valve seals in. What would be the up side of putting on roller rockers on at the same time. What are the benefits? 
Spark Plugs for Big Block? (13/13)
 9/7/09 8:54pm
anips
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because the the roller tip rolls over the tip of the valve stem instead of drag you get less guide wear, you don't have to buy the hi $ full roller ones unless you want to, I run Comp Cams roller tipped  rocker ball and nut type, they work fine for about $140 a set on a street engine.  anips2009-09-07 17:56:35
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