Spark plug types and performance differences

[64\/54Cadillacking]

Ok so I have done a little experiment with my 64.

The engine has been running fine and the idle has been somewhat smooth but not buttery smooth like it's supposed to be.

So I replaced the spark plugs hoping that it might help improve the idle and overall performance. The plugs I had in before were XR5 NGK V-power groove plugs #3332. I replaced them with some Autolite Plats #AP85.

Right away I could tell the engine lacked the power from a dead stop, I mean the power loss was highly noticeable, It was pretty bad actually and the idle from the engine was worse.

I removed the Auto Plats, and bought some new Autolite Coppers #85 and the engine was a little happier.

The idle smoothed out somewhat, and the power gain returned. But the idle is a little shaky, but not as bad as before. Almost like there's a slight miss or hiccup going on.

So after this experiment, I plan on reinstalling the NGK's because they really make the engine as smooth as can be. And the pull from the engine is better with the NGK's as well. It just goes!

My question to everyone is, how come the engine runs the worst with the Autolites Plats, and better with the stock Auto Coppers, and then runs the best with the NGK's?

I would assume the engine would run the best with the Auto Coppers, but this isn't the case. What I noticed bewteen the 2 plugs is that the Autolites are slightly longer than the NGK's. The tip basically sticks further into the combustion chamber than the NGK's do. Does this have an effect on the way the engine runs?

Not sure why this is happening and I hope maybe some of you here that has gone through sets of plugs over the years and found the brand that works for you can help me out.

BTW I checked and gapped the plugs correctly at .35 like it states in the shop manual. Would gapping to .40 help improve things? I have Pertronix ignition installed including a Pertronix coil to allow for a larger gap.

Thanks!

[TJ Hopland]

Have you tried a set of AC coppers?    One thing I have heard is that often times just crossing to a different brand does not get you the exact same heat range plug, the different brands have similar ranges but aren't always the same.  Who knows if AC is making them the same anymore either......

I have heard other people say they have worse performance with platinum plugs in old engines as well as some of the more unique design newer engines. 

[Marcel75]

Hi,

Just to mention that I fitted slightly longer (2.5 mm) plugs on my Eldo 70 and this did not lead to any bad effect on engine performance. The overall behaviour is better with basic ac delco r44xls instead of .... basic ac delco r46n.

[Caddyholic]

I run Bosch platnuim plugs gaped at 50 with the pertronics ignition and flame thrower 2 coil with no issues.

[savemy67]

Hello 64CaddieLacky,

What does Pertronix recommend for the spark plug gap?  The greater the distance the spark needs to cross, the higher the secondary voltage needs to be.  Since you have the Pertronix set-up, the shop manual gap setting may not be applicable.  What does Pertronix recommend for the heat range of the plugs?  Contact Pertronix and ask them what they recommend for your engine.

To some extent, the distance of the plug into the combustion chamber can affect how the flame front propagates.  Also, depending on the condition of your combustion chamber (carbon build-up, valve sealing), the flame front and or combustion pressure may be affected.  These conditions may or may not affect idle and performance.  You can use a scope to check for carbon build-up in the combustion chamber, and you can use a leak-down tester to check the valve sealing.  If you don't want to bother with those items, focus on the characteristics of a few different plugs (heat range, electrode.insulator length) and experiment as you have been doing.

When I bought my 1995 Impala SS in 1995, it came with platinum plugs with four grounding electrodes for each plug.  There is a design flaw with the 1995 LT1 that causes the #8 plug to foul on a regular basis.  This happened quickly with the platinum plugs so I changed to Motorcraft single ground electrode plugs which work fine, and at 192,000 miles, I only have to clean the #8 plug once a year.

Respectfully submitted,
Christopher Winter

[64\/54Cadillacking]

I think what I will do is re-gap the Autolites to .45 and see if that makes a small difference because of the petronix.

I've tried using AC Delco Copper R43S plugs last year sometime, and the car idle like crap. The heat range is 3 on the AC Delco's and 5 on the Autolites. The Autolite Coppers have been second best so far, while the NGK's the best running plug compared to all of them.

I actually have a set of NGK Iridium plugs in my 94 Fleetwood, and it runs perfect. That engine calls for regular Plats, but for durability and longevity, the Iridium's shouldn't foul so easily and last the life of the car, and it's been well worth it.

Seems crazy how NGK's work in just about every vehicle, Foreign or Domestic really well. My 64 seems very picky on what plugs it likes, but it's a good learning experience although frustrating and time consuming.

[dadscad]

I also have the pertronix II and matching flame thrower coil in my 63. I'm also running the Autolite AP85's gapped at the Cadillac recommended gap of .35". These Autolite plugs have about 10K on them and seem to be doing ok. The reason I chose the Autolite plug was that the heat range was the closes match to the factory AC44 the car came with. I came to that conclusion by doing an extensive cross reference between many different brands of spark plugs.

I agree with you that NGK plugs are just great plugs, I run them in everything else I have that needs a plug. Although, at this point I don't remember how close their referenced plug was to the heat range of the AC44.

[cadillacmike68]

I had problems using ACDelco platinum plugs in my 1968 with points & condenser ignition. Poor performance at anything other than idle. An old mechanic then told me never to use platinum plugs in a points system. Pertronix - should be ok. The thing that frosts me is that all the online cats said the plats were ok for my car$%@$@^@#.

So I went back to the R43XLS and the car runs fine. Some years call for R44XLS, very similar but get the correct one.

[64\/54Cadillacking]

Thanks for the replys guys. I believe the plat plugs need a stronger spark to cross the gap vs plain ole coppers which makes sense. But at the same time every engine condition is different, some Cads might run fine on plats if the ignition system is functioning properly and has been converted to Pertronix, others like my 64, doesn't like em at all for some reason.

I am not sure if my Cad has the Ignitor 1 or 2, if it's only the 1, then maybe that is why it doesn't run well with the plats as the spark is weaker. I plan on saving up to get the Ignitor 3 and an MSD Coil and see what happens. Possibly check my distributor for any issues because the engine should run very smooth with the regular Autolite Coppers, but the NGK's are the smoothest running plug, and that to me is odd and shouldn't be normal if you think about it. Maybe there is something about the V-Power plugs that really do make a difference in how it burns in the combustion chamber compared to other conventional style type  plugs.

The engine condition is in great shape after inspecting the NGK's I had in it for a year. All the plugs have a nice grayish/tannish tint on the insulator, no fouling, or burning at all. So I know the engine is running good, including the carb, and it is timed right.

[cadillacmike68]

Thanks for the replys guys. I believe the plat plugs need a stronger spark to cross the gap vs plain ole coppers which makes sense. But at the same time every engine condition is different, some Cads might run fine on plats if the ignition system is functioning properly and has been converted to Pertronix, others like my 64, doesn't like em at all for some reason.

I am not sure if my Cad has the Ignitor 1 or 2, if it's only the 1, then maybe that is why it doesn't run well with the plats as the spark is weaker. I plan on saving up to get the Ignitor 3 and an MSD Coil and see what happens. Possibly check my distributor for any issues because the engine should run very smooth with the regular Autolite Coppers, but the NGK's are the smoothest running plug, and that to me is odd and shouldn't be normal if you think about it. Maybe there is something about the V-Power plugs that really do make a difference in how it burns in the combustion chamber compared to other conventional style type  plugs.

The engine condition is in great shape after inspecting the NGK's I had in it for a year. All the plugs have a nice grayish/tannish tint on the insulator, no fouling, or burning at all. So I know the engine is running good, including the carb, and it is timed right.

That's the main criteria. I wasted money on two sets of plats before finding this out.

[64\/54Cadillacking]

That's the main criteria. I wasted money on two sets of plats before finding this out.

Coppers are better performers compared to Plats anyway. Due to the high compression of both the 429 and your 472, Plats simply don't have the same kind of energy output. I'm sticking with Copper plugs from here on out in my classics.

[cadillacmike68]

Anyone want two sets of 8 very lightly used ACDelco platinum plugs? 

[dino]

Hi
Does anyone have any experience with E3 spark plugs in their 1950's era Cadillac ?
Specifically  E3.52 plugs.  Would like to hear your thoughts..     

[Rod Dahlgren #19496]

OK--- You guys got me going--  But FIRST, I firmly "plant my tongue in cheek" (look it up) And here I go: Spark plugs are an insulated metal rod that transfers electrical energy across an air gap to a metal bar.......  NOW---- given that. the HEAT build in that rod changes depending on the amount of insulation and of course, the metal type used in construction of the rod, shell, and so on...

Now then we have the fact that some manufactures (Champion comes to mind) that actually made a plug (stopped doing this in the 70's) that had an AIR gap between the rod and the connector on top--- Yep, not a solid core---   And then we have the resistor plugs that also have a place inside the plug. Why do we NEED resistor plugs? -------- I'll let someone else respond if you think it is necessary.

Got it???

Now back to just what the heck is my point here? Well -- Not much-- But I figure my "2-cents worth" (look it up) --- Is OK to share. Back in the early 70's, I decided to put a stock Fuel Injection setup on my 57 Chevy. at the same time, I did a fresh complete tune up....  plugs, point, condenser-- all that usual stuff you do.. I put in a set of Champion plugs. Got it all running, road test-- fell flat on it's face. Just about anything more than easy-slow throttle up--- it splattered and would not go...  I blamed the Rochester Fuel Injection. Puled it apart-- rebuilt it AGAIN, back together... BLAH-- same thing.. So back to the injection-- sent out all the nozzles, pump-- and MORE--- back together-- BLAH-- NO GOOD! I yanked off the Injection put back the original Rochester--- SOLD the Injection same day it came off-  (for cheap) ----  Got the car out for a drive------ BLAH-- YUK--- What the HECK? ------- Rechecked everything-- still no good-- replaced distributor, wires-- readjusted valves. NOPE----- So then I changed the plugs-- Put my old AC plugs in-- the dang car ran fantastic...  THAT was when I discovered the Champion plug had that blasted 2-part electrode and that MOISTURE could get in through the top of the plug and cause corrosion between the top and electrode. I have not run Champions since then EVEN though a Champion rep heard about this and came out to tell me they changed the plugs and don't do that anymore---

NOW-- what do I use in ALL my GM cars? ---------- AC plugs -- NON resistor---  Actually, my 57 Chevy STILL has the SAME AC plugs in it that I put in back in the 70's--- Same Points too--- As long as the condenser is good and the point have excellent wear, why would I EVER want to go to an electronic set up that can fail without notice? Last thought ---------  "Keep it Simple" you don't need to look that one up.

[Glen]

  And then we have the resistor plugs that also have a place inside the plug. Why do we NEED resistor plugs? -------- I'll let someone else respond if you think it is necessary.

The high voltage section of the ignition system will create radio interference without resistance in the system somewhere.  In the 60’s the resistance was in the spark plug “wires”.  I put the word wires in parentheses because the conductor in these wires were string impregnated with graphite.  The resistance varied by the length of the wire.  There were problems with the string breaking if the wire was pulled too hard.  That created poor running and was hard to find. 
With resistor plugs you get the interference suppression and equal resistance on each cylinder and real wires in the plug wires.  I had to change the resistor plug wires from time to time until I replaced them with copper wires and resistor plugs.  The copper wires are 20+ years old and still running strong.

[64\/54Cadillacking]

Everyone that I have spoken with that knows a lot about old cars always told me to stay away from Champion plugs. This well known carb rebuilder in my local area that has been rebuilding carbs for at least 40 years and has seen it all has said the same thing to me.

"Stay away from Champs, they are garbage!"

He said Autolites are still a very good plug, but Champs are the absolute worst.

I went to my 64 today and popped off the distributor cap and notice that there's an ignitor 1 is installed. The coil is the old Flamethrower 1 coil which looks like it's been in the car for a long time. This may be causing the slight rough idle at times as if the engine is misfiring occasionally.

I did a spark test and the spark is even and consistent throughout all cylinders. So there is spark getting to the plugs, but the spark from the tester fuse was flashing an orangy color. I am not sure if that is normal or considered a weak spark, but none the less I plan on upgrading the coil and  ignitor to the III version pretty soon..