Hi all.Just pulled the spark plugs out of my '65 L76 motor to replace them with non-resistor plugs.

These are the ACDelco R45's I just put in the motor back in Jan and they have very little milage on them. I'd say less than 1,000 miles since being put in.
Sorry, I know the flash on the different pictures makes them seem a little varied, but all 8 plugs are EXACTLY identical in terms of condition, coloring, etc.
Do they look ok for proper engine operation, fuel mixture, etc?
The one thing that concerns me is that on all of them the threads from approx 11/2 - 2 threads down from the top are slightly wet with oil but the top portion of the threads are nice and dry as is the tip and electrode area.
The pictures of the plugs on each cylinder are here and each picture is marked for which cylinder the plug was in.
http://69.253.166.197/page1/page126/...6/page176.html

 

Barry,

Plugs look pretty normal to me EXCEPT number 4, which has a much shorter center electrode than the other plugs. Verify that visually, and then if it is indeed shorter, would say "something" is wrong! It would not be the same plug as the other 7.

I probably would want a little more burn back on the center electrodes (more heat to burn off fouling), but really would need a better picture (full light and magnified) down the center insulators where fouling occurs. 45's are about as hot as you want anyway. You just need to stand on it more often!

As for the oil on the threads, pretty normal to see this (heads run a lot cooler than the plug electrodes, and once oil wicks up the threads, it either stays wet or turns to carbon towards the hot combustion chamber).

Note that plugs just don't "color" like they did when we had lead in the gas. Makes it much more difficult to tell if the fuel mixture is good. Except when it is really rich or lean, will you see "color". Black insulators are trully rich, and very white insulator are lean.

Here is one website that can be of help in reading plugs (I am sure there are other's as well):

http://www.densoiridium.com/howtoreadusedplugs.php

Plasticman

 

Barry why are you not running projected tip plugs? A too cold standard plug who probably only last about 1000 miles before it started to miss.

 

Plasticman
good eye. I didn't notice that difference on the #4 plug but checking it visually just now it IS shorter than the others. The odd part is that the gap looks the same as the others (if the electode itself was shorter from being worn away or burnt away somehow I'd expect to see a bigger gap).
While the electrode itself looks shorter it also looks as if the insulater around it is higher up than all the rest. It seems to me as if maybe the insulator was not installed seated all the way down and is sitting higher therefore just covering more of the electrode??
Maybe it was just a defective plug the way it was manufactured??

 

C2

no one ever recommended to me to run an extended tip plug.
JohnZ and most others recommended the R45's as the best overall plug to run so that's what I put in.

If I ran an extended plug don't I have to worry about piston clearance?
I have NO IDEA what pistons are in my motor - flat top or domed or what. Would a domed piston cause clearance issues on an extended plug?

 

I don't think the extended tips would be any issue with respect to piston clearance even with 12 to 1 pistons. Extended tip plugs are somewhat self cooling so you can run a hotter plug to eliminate fouling issues and still have no pedal down issues. If you're going to run regular ignition (points and coil no amplifier) this is the only way you'll ever have any plug life. I don't run AC's I use autolites and if I'm driving around with the occasional full throttle pass I use a 6 heat range. Like a 16 in peanut plug and I think you're application would be a 56 but I'd have to look. I'm sure AC makes a similar plug.

 

Bob

well, it was recommended that one area to look at to try to solve my problem was a non-resistor plug so I'm going with the NGK B4 plug and see if it makes a difference.
Now, I never had a problem running the AC R45's before because that's what was in the car previous to my replacing them in Jan anyway. I don't find a problem with the 45's heat range so the B4's should be the same I believe.

 

Think I would look hard at that one plug with the short electrode. May be the cause of your issues. Think it probably is a colder plug that was marked incorrectly. Or was a poor assembly to begin with. Try your new plugs, and see how they work (did they solve your problem?).

The extended tip (also called projected core) plugs are indeed "better" for most SBC applications (in my view).

There was a time when I had to replace plugs every 2K miles due to Hi RPM breakup (back in the mid 70's on my 70 Vette SBC 350-350). Got to be a real expert at changing plugs in a hurry. The extended tip plugs helped that situation, but never cured it (as gas octane quality was "revised").

As for the non-resistor plug solving your issues, rather doubt it! If anything, the one short electrode is more likely at fault, or there is another issue (poor fuel mixture, ignition issue, etc,).

Plasticman

 

The AC's use S for extended tips so I would guess the matching plug would be an R45S? That standard ignition is wimpy do yourself a favor and buy some kind of amplifier (I like the MSD but I bet there's plenty of others) and hide it somewhere if you want the car to look stock. Then all this becomes a non-problem and the throttle response will improve, particularly if you can run a wider plug gap (MSD's tolerate a 45 or 50 thou gap). BTW if you're going to run conventional ignition at least check the rotor/cap indexing I've seen these really screwed up and that kills ignition efficiency.

 

Barry,
those plugs are not the issue...

unless you have a cracked electrode or something that isn't visable in the pix, but they aren't wet, and they aren't pitch black, nor are they deteriorating from a lean mixture...
the problem is somewhere else...
those plugs have plenty of miles left (assuming that one isn't damaged)

as far as resistor vs nonresistor plug, the R45 provides more than enough spark to accurately and correctly ignite an L76 motor... with points and a coil... if it is all setup, an MSD box or fancy ignition will not improve anything, it will just mask the current problem.

Also, an extended tip can cause piston to plug clearance issues ( depending on how much your heads are decked and how thick your head gasket is) the last thing you want to do is push your piston into the plug when you turn the motor over the first time.

have you changed the points, coil, and condensor yet?

thats where the real problem lies I bet.

thanks

Aaron

 

Aaron

I'm changing the plugs to go to a non-resistor plug as it's been suggested by someone whose opinion I GREATLY respect that there is a possibility that between the new ignotion wires and the resistor R45 plugs that there could be a voltage drop enough to cause my missing issue. He had the same problem on his car and went through everything such as carb, points, coil, and others without success and finally replaced to a non-resistor plug which solved the problem.
It may or may not work for me but it's a starting place. If the non-resotor plugs don't work than I'll go one item at a time down my list, including the coil, points, checking the valvetrain, etc. but i need to start somewhere.

I was only asking about the condition on these R45's that I just pulled out simply since I had them out I wanted to make sure there weren't any other issues (not related to my missing problem) that I should be aware off such as a completely wrong mixture problem, or whatever. It was just a simple checking to make sure that all the cylinders seems to be OK, burning evenly, and without any major issues.
I wasn't asking for a plug evaluation on these plugs as a cure for my missing problem

I agree that items such as an MSD igintion box aren't needed and I wasn't considering one or other modern "hot rod" products.
there is a simple reason for my missing problem and i'll find it eventually as I go down my list one single step and item at a time.

 

A question for Aaron, if high output ignition systems gain you nothing why has the entire worlds automotive manufacturers changed over? Where do the 100,000 mile plug change intervals come from? With a standard ignition system a set of plugs is good for about 10 passes at the drag strip before the car starts slowing down due to the plugs even if it's not missing. With an MSD this issue disappears. With conventional ignition a few thousand miles (or less) of driving around and you get a plug miss under heavy loads/5000+ rpm. An MSD fixes this and plugs will last 10's of thousands of miles with no issues.

 

Back when I raced on a regular basis I was told to look closely at the box a set of eight AC plugs were packaged in. There were hash marks on the corner of the box that (apparently) indicated the varience of heat range between plugs within the box (more hash marks = greater varience). It may be a pre-Internet urban myth (a good racing joke, along with blinker fluid and using a curb feeler as a pre-stage indicator) but when we sorted the boxes of AC plugs and only used packages marked with two or three hash marks we found more consistent power and ET's and a longer plug life.

Regardless of the hash marks, the plug center electrodes should all look the same regarding depth, thickness and height of the insulator. The surface area of the insulator determines the heat range and it's heat transfer performance.

I would also test the wires for shorts. Leave the ignition shielding off and run the engine in the dark to expose arcing from wires to the block or accessories. Run the rpm up a little and look for arcing from each wire.

We used to recommend this plug wire inspection procedure with simple advice to "just close the garage door and look for arcs for a minimum of half an hour" (to all our Mopar racing friends, because of thier cars superior enginerding). GM owners need to keep the inspection area well ventilated (the cars may not be as sophisticated, but the owners are, and we hope to keep it that way ).

 

Bob, you hace to compare apples to apples here...

my stock DZ302 as well as a stock L76 (which i recently converted to L84) runs well over a few thousand miles before even coming close to fouling plugs... if you are talking about a full blown race setup where you are trying to squeeze as much fuel and air into the chamber, then sure, an MSD or Crane or Mallory unit will probably serve you better. But MSD, Mallory, and the like, are not going to make profit selling you points either.. so there is certinaly some marking involved... about 15 years ago, Smoky Yunick did several dyno tests that proved that in typical street and race applications, there was now power to be gained from using high current boxes in gasoline (non-nitrous) applications.

this instance is a bone stock L76... that is street driven. not a full blown race car.

I've run conventional ignitions for years, and never foul plugs... but all of my motors are setup correctly... they all run great, and i've never had issues.... the minute you start changing things.. the equation changes...

my words to Barry were that it is highly unlikely that the plugs or wires are the issue here, especially if since his motor is a stock setup. If he is using some 8.8mm accell 300+wire, then maybe., but i was under the assumption that he was using fairly stock componants....
that being the case, a stock points type ignition, with stock coil, stock wires R45 plugs will run for several thousand if not 10s of thousands of miles without a problem....

i've mentioned about my 64 bonnieville before.. I built the motor 10 years ago to stock specs except used the 421 HO cam. it was a daily driver for 9 years... has over 100k miles on the motor and only had the points and plugs changed 3 times over that span... still had the same wires on it... nothing fancy, but for a stock application, it worked perfectly... the motor is now a 421 with a wild Ultradyne solid flat cam, almost .600 lift, and it now has 6000 miles on the motor, same plugs that I broke the cam in, and they look great... again, stock points, stock coil, stock everything.

so... unless you are doing heavy modification to the motor, the factory ignition system is more than accurate for long term durability and reliability....

however, having said that... you have to treat them like they were intended to be used, which means routine starting and driving. Letting points sit over the winter and not firing up a motor for 6 months isn't a good thing for these cars.

Aaron

 

Barry,

sorry, I thought you were looking for an evaluation on the plugs...

the truth is that from the way they look, they are firing properly.
your miss is not coming from an issue with them, the amount of voltage at the tip of the plug is not going to make the miss go away...

that is what I was trying to say..

I'll politely wait to hear your results

 

I'm NO expert (and of course not Aaron who you directed the question to) but the I look at it is like this:

a lot of people change over to electronic conversion systems such as the Pertronix or Breakerless SE etc. I see no advantage to it as it only replaces the switch from an electro-mechanical switch to an electronic switch. Less reliable than points overall and if it fails you are stranded unless you are carrying a $160 spare unit with you rather than a $10 spare set of points. There is no additional spark to gain any performance.

The HEI systems I believe did add more spark as this was required at the time because of changes to the ignition timings, fuel mixtures, and emisions related "crap" installed on the cars to reduce emissions.

More modern type ignition systems now can't even really be compared at all can they because they are so different with computer controlled everything. The computer systems can change just about every aspect of how the engine runs many times a second with the fuel mixture, timing, etc, etc that motors are running so much more effeciently that I'm sure that is a large reason for longer lasting spark plugs, less frequent tune-ups, etc.

I'm sure I'm missing many other major aspects of the entire subject and than again I may be completely off base and 1000% wrong......

 

I was.......... just not for the reason that I suspected the plugs to be fouled or anything like that and expected my miss issue to be the cause of that.
simply that while they were out since I am replacing them I wanted an evaluation as a completely and seperate matter just to make sure everything in general looked OK with them.

I'll post up as soon as I get the new plugs (tomorrow) and try them out.

Thay may or may not solve the problem but like I said it's a starting point in my quest to fix the problem. If theyt don't make a difference I'll continue on

 

Are you going to install the new ones - remove them, and read them ?

There is a method (someone else may can post it ? ) about how you should run the car to get a good burn indication on the plugs to tell what is going on.

I know the NASCAR boys will shutdown their motors at a high rpm, coast all the back to the pits and pull the plugs to read them. I think you want to keep it at a high rpm, shut the motor off and pull the plugs. If you just idle around, they will show a different color than when you are at higher rpm's....I know, hard to do on the street.

 

Grey

h*ll no!! After the hassle these things are to take out and put in once I get the new plugs in tomorrow they are staying in!

I wasn't aware that that with changes to gas, etc that plugs are harder to read now than in the past.
A friend emailed me after seeing this thread I started and basically said the same thing you just did.
This is what he said:

"With current gas, reading plugs is not what it used to be. If anything the motor looks to be a little lean but you really can't get a good read unless you run the motor under load and immediately put in the clutch and shut off the motor then read the plugs. Hard to do on the road.

If you let the engine coast down, the air fuel ratio will change and the color of the plugs will also change so the reading is not representative"

that is basically the same as what you described as how the NASCAR guys do it.

Regardless, I think I've learned enough about any readings I'd get off my plugs in any case. They all pretty much look relatively "normal" and all look pretty much equal and even from one cylinder to another so at least I think I know my motor is working "OK" without any particular cylinder or two doing something totally different than the others.
The only exception looks to be the #4 plug as Plasticman noticed but I think that will turn out to be nothing more than a defective plug from the start.

 

Barry, the plugs I've always recommended are the R45S, which are the extended-tip plugs; I run them in all my small-blocks, including my 11:1 domed-piston stock '69 Z/28 with point ignition, stock coil and plug wires, which pulls 7000 with nary a miss, ever.