Spark Plugs Revisited

[74bigblock]

OK, So my last post did not really provide me with any answers to my questions. I thank those of you who provided input, but I need more details, and no one is responding to that post. So, I thought I would start over.


The Question:

How do I determine which spark plugs are correct for my vehicle?

What heat rating do I need?
What size plug do I need?
What gap? (I've seen 35-45, so should I just gap at 40???)
Are "platinum" plugs a bunch of bologna or are there real benifits to them in my motor (see below for my motor)?

The Playing Field:

I don't want to rely just on the "configurators" on certain websites... as they assume my motor is stock. With that said, I have a 1974 454 LS4 motor that is bored 30 over. Hit has Hyd. roller rockers, an agressive cam, and I have upgraded the ignition to HEI 50K.


Thanks again...
Dave

 

[JohnZ]

AC R45XLS is a good all-around normal-driving plug for a BB - the "5" heat range works well for 99% of your driving, "4" for hard duty (dragstrip passes), and "3" is too cold for normal operation - can foul around town. .040"-.045" gap should work fine, and forget the whizbang miracle unobtanium plugs of any description; they'll just lighten your wallet. Check your plugs occasionally for color based on your driving habits - insulators should be a tan color; if they're white the plug is too hot, if they're black the plug is too cold. Plugs don't make horsepower - they just light the fire, and if they're the right heat range for your driving habits, they'll give you good service.

 

[Vettehead Mikey]

OK, So my last post did not really provide me with any answers to my questions. I thank those of you who provided input, but I need more details, and no one is responding to that post. So, I thought I would start over.

Maybe that's cause you got the answer to your question in the first response to the original post, and nobody else saw the need to repeat it.

"Stock type plugs, stock gap. Choose whichever manufacturer strikes your fancy, they're all the same. Everything else is marketing BS and will make no difference."

JohnZ is far more diplomatic than I, and went to the trouble of spelling it out for you.

 

[74bigblock]

Maybe that's cause you got the answer to your question in the first response to the original post, and nobody else saw the need to repeat it.

"Stock type plugs, stock gap. Choose whichever manufacturer strikes your fancy, they're all the same. Everything else is marketing BS and will make no difference."

JohnZ is far more diplomatic than I, and went to the trouble of spelling it out for you.

Hey Mikey... I don't know jack about plugs... I don't know what the stock plugs are, or what the stock gap is/was. So if they are all the same, by your method... I can go take the plug out of my lawnmower and run that???

Real nice. I don't really appreciate your sarcasm (intended or otherwise)either.

 

[74bigblock]

AC R45XLS is a good all-around normal-driving plug for a BB - the "5" heat range works well for 99% of your driving, "4" for hard duty (dragstrip passes), and "3" is too cold for normal operation - can foul around town. .040"-.045" gap should work fine, and forget the whizbang miracle unobtanium plugs of any description; they'll just lighten your wallet. Check your plugs occasionally for color based on your driving habits - insulators should be a tan color; if they're white the plug is too hot, if they're black the plug is too cold. Plugs don't make horsepower - they just light the fire, and if they're the right heat range for your driving habits, they'll give you good service.

John,

Thanks for "spelling" it out for me. This was the answer I was looking for.

Dave

 

[lucky76]

Hey Mikey... I don't know jack about plugs... I don't know what the stock plugs are, or what the stock gap is/was. So if they are all the same, by your method... I can go take the plug out of my lawnmower and run that???

Real nice. I don't really appreciate your sarcasm (intended or otherwise)either.

Now..Now Guys...... You'll need 8 of those lawn mower plugs!

 

[Hib Halverson]

(snip)
The Question:

How do I determine which spark plugs are correct for my vehicle?

Start with the recomendation in the AC Delco or Denso spark plug catalog.

What heat rating do I need?

Actually it's "heat range" and the proper heat range depends on the engine's duty cycle. The typical street high performance duty cycle "likes" a plug one range colder than stock. That suggestion is contingent on 1) the engine being in good condition, 2) no starts without warm-ups and 3) the car gets driven hard.

What size plug do I need?

stock, which is 14mm thread, 5/8-in hex, .460-in reach

What gap? (I've seen 35-45, so should I just gap at 40???)

In the end, the perfect gap takes some testing but, since you have HEI, I'd start at .050 with std. plug and .060 with platinum or iridium plugs.

Are "platinum" plugs a bunch of bologna or are there real benifits to them in my motor (see below for my motor)?

Spark plugs with platinum or iridium tips will increase spark plug durability and in some cases make an incremental improvement in performance. Unfortunately, there is a lot of "snake oii" out there in platinum plugs...the Bosch platinum line for instance, especially the "plus 2" or "plus 4" products. If youi want good plats, the ACDelco Rapid Fire line is a good choice. The best spark plug in the industry right now, IMO, is the Denso Iridum Power. Unfortunately, Densos are a bit expensive. The Rapid Fires are, also, more costly than ordinary plugs but are less expensive then Densos.

The Playing Field:

I don't want to rely just on the "configurators" on certain websites... as they assume my motor is stock. With that said, I have a 1974 454 LS4 motor that is bored 30 over. Hit has Hyd. roller rockers, an agressive cam, and I have upgraded the ignition to HEI 50K.

Thanks again...
Dave

I suggest either the AC RapidFire #1 or the Denso ITF20. Those are the plugs I use in all, iron head, street hi-po small blocks and big blocks. If the car is not run hard, ie: a show car or it's a car that sees frequent starts without warm-ups, i'd use the AC RF2 or the Denso ITF 16.

 

[74bigblock]

Way to break it down Hib!!!

I will consider your advise thouroghly.... as I am all cast iron right now... and I do flog the :W out of her on a regular basis.

Thanks!
Dave

 

[Vettehead Mikey]

Hey Mikey... I don't know jack about plugs... I don't know what the stock plugs are, or what the stock gap is/was. So if they are all the same, by your method... I can go take the plug out of my lawnmower and run that???

Real nice. I don't really appreciate your sarcasm (intended or otherwise)either.

I assumed that you had at least looked in any one of the basic shop manuals or other literature available for your car to learn what the basic equipment consists of, and were falling into the shade tree re-engineering black hole where Bubba lives.

I regret making that assumption and retract my post above..

 

[74bigblock]

I assumed that you had at least looked in any one of the basic shop manuals or other literature available for your car to learn what the basic equipment consists of, and were falling into the shade tree re-engineering black hole where Bubba lives.

I regret making that assumption and retract my post above..

I am Bubba's Nephew... Putz.

 

[curtis]

I got a higher idle speed just by installing Bosch Plus-4. That tells me they make the engine burn the fuel better. No snake oil needed. I like what I run and see no reason to change to a relic type plug. I am not related to Bubba either.

 

[74bigblock]

a relic type plug.

:cry

 

[74bigblock]

In the end, the perfect gap takes some testing but, since you have HEI, I'd start at .050 with std. plug and .060 with platinum or iridium plugs.

I suggest either the AC RapidFire #1 or the Denso ITF20. Those are the plugs I use in all, iron head, street hi-po small blocks and big blocks. If the car is not run hard, ie: a show car or it's a car that sees frequent starts without warm-ups, i'd use the AC RF2 or the Denso ITF 16.

Hib,

I've decided and purchased the Rapidfire #1, as my driving habits regularly see full temp and longer duration cruising, as well as a number of red line runs on each cruise.

With this choice, you recommend I start at .050 for the gap. How do I know if I should decrease or increase the gap/ what are the indicators? What is the best method for testing?

Thanks again!
Dave

 

[Hib Halverson]

Hib,
(snip)
With this choice, you recommend I start at .050 for the gap. How do I know if I should decrease or increase the gap/ what are the indicators? What is the best method for testing?

Thanks again!
Dave

Road testing is the best method.
This discussion assumes there are no other problems with ign. and that the engine is in good condition.

Now, with .050, if the engine idles more rough than before or misfires under load where it didn't before, close the gap to .040....and send back that aftermarket HEI as it ain't working right. If .050 works ok, you can try .060 and run the same test. My guess is that .050-.055 will work just fine.

I got a higher idle speed just by installing Bosch Plus-4. That tells me they make the engine burn the fuel better. No snake oil needed. I like what I run and see no reason to change to a relic type plug. I am not related to Bubba either.

Bosch's marketing staff break out in poop-eating grins when they read stuff like that but real spark plug engineers giggle at marketing ploys such as the Bosch Plus-4. It's a great attraction to laypeople/consumers because of the racy-looking, four-ground electrodes, the silvery finish and Bosch's great advertising.

The problem is it's a poor spark plug design....IF the goal is high performance.

Anyone who understands combustion dynamics and ignition will tell you the more of the charge air you can expose to the spark, the quicker and better the mixture in the combustion chamber will ignite and burn away from the plug. In fact, this is why racers cut-back and file-to-a-point their side electrodes. It's why OE's put spark plugs where they are exposed to intake air flow and why some plugs have very projected tips and...it's why OE and other plug makers with very exceptions (mainly some rotary engines and a few Asian inline-fours) do not use plugs with multiple electrodes.

What Bosch does is obstruct the spark from charge air by putting four side electrodes in the way.

You might think you're getting lots of extra performance because your idle speed went up. I hate to tell you this but, the only increased performance associated with the Bosch Plus-4 is that of Bosch's profit/loss statement.

 

[74bigblock]

Road testing is the best method.
This discussion assumes there are no other problems with ign. and that the engine is in good condition.

Now, with .050, if the engine idles more rough than before or misfires under load where it didn't before, close the gap to .040....and send back that aftermarket HEI as it ain't working right. If .050 works ok, you can try .060 and run the same test. My guess is that .050-.055 will work just fine.

Thanks Hib! I will start her out at .050 and see how she does. I am fairly confident the igition system is in tip top shape... as I just replaced the entire distributor with a new HEI with manual tach drive unit from Mid America (some people think this is a poor system, I happen to think it works great for a street car with some hairy cahones)!!!

My new plug wires and seperators get here monday, so I will regap the plugs and install them... do the wires Monday, and hope for clear weather! I did notice that the plugs came out of the box with gaps ranging from .030 to .047. I thought that was weird.

-Dave

 

[jdp6000]

How crucial are the wire separators? I have new everything but still get a miss. I have purchased wire separators but have not installed them.

Jim

 

[JohnZ]

Wire separators are important, especially in avoiding cross-firing between #5 and #7, which fire sequentially.

 

[74bigblock]

Well, I got all the plugs in. What a PITA on cyl #1, #3, and #7! Especially with the side mount headers. Anyhow... after some fudging... they are all in and the car fired fine. Monday I will do the wires and see how she runs!


Dave

 

[jdp6000]

Wire separators are important, especially in avoiding cross-firing between #5 and #7, which fire sequentially.

Thanks for the reply John,

I have them so I may as well put them on.

Jim

 

[curtis]

Hib, I respect your opinions, but you may wish to review some of the testing done to Bosch Plus 4 plugs. Check out the FAQ section at this site. http://www.boschusa.com/AutoParts/SparkPlugs/PlatinumPlus4/
I don't believe it is all just hype.