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Some of you cats might enjoy this very informative article; I learned some things.


http://www.dragzine.com/tech-stories/ig ... m-opinion/

Great article. Just like a Doctor checks your organs for signs of failure, a Mechanic looks at spark plugs for hidden issues inside the engine. I had a 1974 Chevy van with 356,000 miles on the original engine. Over the decades I had the trans rebuilt twice, 2 water pumps, several starters and alternators, but never had the heads off or rebuilt the carb. As it got older, I noticed a few of the plugs were getting fouled from oil. I simply put in a hotter plug in that cylinder and merrily puttered down the road. After a few more thousand miles when I noticed a miss, I ended up putting in a plug that was twice as hot, or tried a different brand in that cylinder. At one time when it was over 300K miles, I had an assortment of Autolite, Champion, A/C, and Motorcraft plugs in it, and it purred like a kitten. I eventually had to scrap the van because the body and frame were rotting away, but that ol' Chevy 350 engine started up every day and took me to work or on vacation. In fact, I drove it to the scrap yard 10 years ago and they gave me $600 for it. They couldn't believe how great the engine ran.

Back in the mid 80's, I worked at a company that had a race car, which at the time ran in the Kelly American series. At Daytona, about 20 laps from the end of the race, the alternator went out. No big deal, plenty of battery left to finish. Later, in the pit, all of the plugs were pulled, as a Champion spark plug guy (old man) would come by and give a reading of the plugs. He had a jewelers loop affixed to his glasses. He read the plugs and as he was walking away, he turned his head and said fix your alternator.

Some 30 years later, I am still amazed by that.

Over the years I've built a few hopped up Harley engines and got pretty good at reading spark plugs and indexing plugs . There really is a science to perfect firing plugs .

hogv8 wrote:Over the years I've built a few hopped up Harley engines and got pretty good at reading spark plugs and indexing plugs . There really is a science to perfect firing plugs .

Not intending to hijack the thread but drawing off your mention of hopped-up Harley's, I was AMAZED to see NHRA Top Fuel Harely's running low 6's/high 5's in the 1/4 mile.

The Mindless Philosopher wrote:

hogv8 wrote:Over the years I've built a few hopped up Harley engines and got pretty good at reading spark plugs and indexing plugs . There really is a science to perfect firing plugs .

Not intending to hijack the thread but drawing off your mention of hopped-up Harley's, I was AMAZED to see NHRA Top Fuel Harely's running low 6's/high 5's in the 1/4 mile.

And probably running the same Champion plugs I was running 20 years ago.

Jack wrote:

The Mindless Philosopher wrote:

hogv8 wrote:Over the years I've built a few hopped up Harley engines and got pretty good at reading spark plugs and indexing plugs . There really is a science to perfect firing plugs .

Not intending to hijack the thread but drawing off your mention of hopped-up Harley's, I was AMAZED to see NHRA Top Fuel Harely's running low 6's/high 5's in the 1/4 mile.

And probably running the same Champion plugs I was running 20 years ago.

Actually had better luck with NGK,s .

Ya know, I run the short NGKs in my bike because of header interference, and I have not enjoyed them. Could be my ignition system and not the plugs, won’t know until I replace it.

I'm running AC Delco FR5LS in my ZZ4 per a recommendation by Adrian (may God rest his soul) several years back. So far so good.

The Mindless Philosopher wrote:I'm running AC Delco FR5LS in my ZZ4 per a recommendation by Adrian (may God rest his soul) several years back. So far so good.

The correct spark plug is a AC Delco MR43LTS to be gapped at .040 with anti-seize applied to the threads because these spark plugs are stainless steel.

Is this the new number that replaces the ac delco FR5LS? I think I was told this a NAPA a couple of months age when I tried to purchase the FR5LS plugs .

The video specifically said not to put anything on the threads. :p

hogv8 wrote:Is this the new number that replaces the ac delco FR5LS? I think I was told this a NAPA a couple of months age when I tried to purchase the FR5LS plugs .

No, this is not the new number. This is the Spark plug GM Performance recommended for the ZZ4 350 crate engine since the beginning of time. LOL! I went around and around with Adrian about this a few years ago. God bless his soul.

Jack wrote:The video specifically said not to put anything on the threads. :p

I don't care about what that video says about not putting anything on the threads! If you don't apply anti-seize to the threads of a stainless steel spark plug into an aluminum cylinder head you will basically weld that plug into the cylinder head. This is caused by the two dis-similar metals. Aluminum and stainless steel. That's a fact, Jack! LOL!

Ran a quick check on the MR's over here [UK] - and found these are a Special Marine plug for GM Mercruiser.

They might be slightly cheaper than the FR's but would also be good to know if you found the MR's run better in any way?

I have the ZZ4 350 hot cam so they might be worth trying.
Just out of interest, are the MR's also good for the 502?

I don't know if they are any cheaper than the FR's. That isn't the reason I use them. The reason I use them is because GM Performance Division (where Boss Hoss get their crate engines from, except for the 383 Stroker) recommend that particular spark plug. You might want to give them a call and see if the heat range is adequate for use with your hot cam. I don't have a hot cam in my ZZ4. These plugs made a BIG difference in my performance over the FR's. Also, NOW my engine NEVER stalls at an idle like it used to using those FR's!! I have fuel injection.The best thing since CAN BEER!! LOL!! Call GM Performance @ 1-866-453-4123 for any tech questions you might have. I don't know the answer about using the MR's in a 502. Good luck!

I have the GM Hot Cam , 1.6 roller rockers and a Edelbrock with the stage ll mod and the FR's are what Adrian recommended to me when I asked him about 15 years ago and I've been running them ever since with great results . Now maybe your stock engine with fuel injection runs better with the MR's .My engine runs like a raped ape , starts perfectly and never stalls so I'll stick with what works for me and I think you will
do the same Ron .

Ron Radulski wrote:

Jack wrote:The video specifically said not to put anything on the threads. :p

I don't care about what that video says about not putting anything on the threads! If you don't apply anti-seize to the threads of a stainless steel spark plug into an aluminum cylinder head you will basically weld that plug into the cylinder head. This is caused by the two dis-similar metals. Aluminum and stainless steel. That's a fact, Jack! LOL!

My plugs like to defy the fact. On the contrary, I have to inspect tightness all the time. #7 and #8 love to get loose on their own (especially #8). So far I've only ever had to re-tighten them and also #6 to a much lesser degree. The rest are fine. No problems with them seizing, but then I haven't exactly been able to rack up the miles, either. No telling what the future holds. I would say the anti-seize is working.

Ron Radulski wrote:I don't know if they are any cheaper than the FR's. That isn't the reason I use them. The reason I use them is because GM Performance Division (where Boss Hoss get their crate engines from, except for the 383 Stroker) recommend that particular spark plug. You might want to give them a call and see if the heat range is adequate for use with your hot cam. I don't have a hot cam in my ZZ4. These plugs made a BIG difference in my performance over the FR's. Also, NOW my engine NEVER stalls at an idle like it used to using those FR's!! I have fuel injection.The best thing since CAN BEER!! LOL!! Call GM Performance @ 1-866-453-4123 for any tech questions you might have. I don't know the answer about using the MR's in a 502. Good luck!

My setup is using a pair of "Captain's Bars" heads (L-94??? I can't remember without going to look it up) for some reason (I keep reading that they are not a good choice for this setup). They have 1.5 stamped steel rockers. I have been told my cam is not the 385 HP "Hot Cam" but that it is a similar aftermarket grind. That said, I am not opposed to trying different plugs, especially based on the words of the experienced.

Hey Mindless Philosopher, you don't need to use anti-seize if you're running the FR's in your engine, they do not have stainless steel threads like the MR's. So there's no need to use anti-seize on the threads. I would try the MR's on your engine though if your plugs keep getting loose on you. It could be because the FR's have a compression washer on them which is intended for use on the cast iron cylinder head, NOT the ZZ4. Where as, the MR's have a taper machined above the threads of the spark plug where it mates perfectly to the taper machined area on the ZZ4 cylinder head. Are your heads aluminum? Check your "Captain's Bars heads to look for this taper before using the MR's.

Ron Radulski wrote:

Jack wrote:The video specifically said not to put anything on the threads. :p

I don't care about what that video says about not putting anything on the threads! If you don't apply anti-seize to the threads of a stainless steel spark plug into an aluminum cylinder head you will basically weld that plug into the cylinder head. This is caused by the two dis-similar metals. Aluminum and stainless steel. That's a fact, Jack! LOL!

Hey! I did the .... that means I'm kidding!!! The video was more a commercial than anything, to me at least. I'll continue using a dab on the stainless plugs, like I do with EVERYTHING stainless... and I recommend the same for everyone else.

I like stainless bolts also and use them everywhere I don't need strength . Stainless isn't as strong as steel .

Ron Radulski wrote:Hey Mindless Philosopher, you don't need to use anti-seize if you're running the FR's in your engine, they do not have stainless steel threads like the MR's. So there's no need to use anti-seize on the threads. I would try the MR's on your engine though if your plugs keep getting loose on you. It could be because the FR's have a compression washer on them which is intended for use on the cast iron cylinder head, NOT the ZZ4. Where as, the MR's have a taper machined above the threads of the spark plug where it mates perfectly to the taper machined area on the ZZ4 cylinder head. Are your heads aluminum? Check your "Captain's Bars heads to look for this taper before using the MR's.

Yep. They're definitely aluminum heads. That would explain it. Thank you.