My 454" ate up three sets of R45XLS spark plugs awfully fast so I searched for a platinum or iridium replacement. After a lot of internet searching I finally found #3405 platinum Champions would interchange so I have been running a set since spring of this year. They are doing a great job and wearing very slow but I wanted to try #5305 DENSO iridium plugs to see how they compare. I just bought a set for only $6.32 each plus tax and shipping which is a LOT cheaper than the $9 to $11 that most vendors are charging (Walmart's price was a pretty low $7.50). The iridium spark plugs are considered the very best as platinum will withstand very severe heat and the Denso plugs feature a fine-wire .016" diameter (.4 mm) center electrode with a V-groove ground electrode.

The advertising claims 120,000 mile life span for these fine-wire DENSO plugs so these plugs could last 8-10 years. If so they would certainly pay for themselves in their life span alone. Can't wait to try them.

 

Buy a set of AC Delco's your Vette came with for 30 bucks, change them after 50,000 miles and your saving a lot of money instead of silly gimmick plugs

 

We humans are odd as we often buy products solely because of their cool names. Names such as "Air Gap", "Brute", "BlackWing", "Double Pumper", "Filter Charger", "X-Ram", "E-Street", and "Team G". The product could be a horrible misapplication but yet we'll buy it anyway just for it's name alone so we can brag about owning one too.

I have a barely functioning 76 year old drunk neighbor who can't read or write, has the IQ of a sea slug, and no mechanical knowledge or skills whatsoever. When I showed him my engine one afternoon he spotted my #3310 Holley and immediately said "ah, you got a double pumper" without having the foggiest idea of what a double pumper is. Somewhere along the line he saw a Holley and heard the term "double pumper" and the name stuck. To him all 4-barrel Holleys are double pumpers whether they are or not.

In the world of advertising names sell like hotcakes so if a product is given a cool name that name alone will sell the product.



Hmm, Denso Iridium, cool name, I see why you bought them.

 

Didn't we go through this a few weeks ago?

https://www.corvetteforum.com/forums...ig-blocks.html

 

My wife's pickup came with iridiums from the factory. Ran great until about 80K miles. Started getting lean mis fire codes...but would run like crazy at WOT and never miss a beat. Decided to ck plugs and found the gap was worn incredible. I swear it looked like .150"+ easily. Went to buy new plugs and they were out...so I bought the basic standard Autolites to see if they would cure the issue.

Guess what? It ran another 80K miles and started having occasional misfires and setting lean codes. Plugs actually looked a lot better than the first set...but a new set took care of the issue.

So not sure if you're going to ever notice the difference if the rest of the ignition system is up to par. OEM's use them because they have to guarantee emissions for so long...and they get a good margin on them.

Certainly good plugs are good...but when N/A I ran basic extended tip A/C Delco's all the time making just under 900 HP. They literally lasted for years on the street and track..never really saw wear..just changed them occasionally when heading to the track. Actually just put them back in after the track if I did change them...nothing wrong with them.

JIM

 

The #3405 Champions are doing great when compared to the pitiful R45XLS AC Delcos so I'm curious how well these #5305 DENSO will work. I recently saw a AC Delco plug that said AC Delco/DENSO so I'm wondering if there's a connection between the two.

 

I guess all of my stuff has been "plug neutral" over the years. I typically use NGK's when feeling serious about racing...but truthfully I've run just as fast with the "wrong" super hot, extended tip A/C's I used on the street. Dyno guy used to look at me and say "could you have found a hotter plug"? But they worked great with huge cams and Dominator carb. Never fouled and pulled past 7500 RPM anytime I wanted.

Heck even ran points for years for the conversation topic. Dyno'd back to back with them...they did fine through the 7000 RPM range and 800+ HP with a 7 year old set of points! They did start bouncing a little at that RPM...but I didn't have a new set with me to test.

Nothing wrong with the higher $$$ plugs and if they work for you...then I'd use what works.

I'm just always curious as to "why" something works better. Is that plug a lower resistance that's helping with a weak ignition system? Is it extended or recessed when the previous one wasn't? Are the threads putting it deeper/shallower in the chamber? A plug pretty much just needs to fire and do it well. And they will only carry as much current as necessary to jump the gap. Nothing extra... Certainly some can last longer..but is it wear or fouling that makes them get changed? Can't imagine most folks here to wear out many plugs....


JIM

 

Copper is actually a better conductor than platinum or iridium. The difference is in the longevity of the plug. Platinum will last much longer than normal plugs. I've seen figures that say iridium plugs will last about 15% longer than platinum. Where this makes the biggest difference is in motors where the plugs are hard to get at. I just did my wife's Saturn VUE and the plug change took a day and a half. Interestingly, the stock plugs on that motor were those 4 electrode platinums. After 150k miles, they were quite worn but didn't look terrible.

 

As both of my Honda generator engines and my 5 hp Tecumseh air compressor engine also use the R45XLS heat range and style of spark plugs I'll use my present #3405 Champions in them so they don't go to waste.

I have been wanting to try out the #5305 DENSO fine-wire iridium plugs to see if they'll outperform the #3405 Champion plugs that are already giving me good service. The DENSO center electrode is only .016" diameter so it'll give a good hot spark and they're claiming a 120,000 mile life span.

Spark plug gap. Standard Motor Products recommends a .035" gap for HEI plugs because a .045" gap is pushing the limits of the HEI coil. Its okay to run the wider .045" gap IF that gap is maintained and I found out the hard way .055" is the maximum gap an OEM HEI coil will handle before the plug quits firing. So its better to run the standard .035" gap to compensate for the wear it'll get. If the DENSO iridium plugs don't wear much I might try the .045" gap even though there's no performance advantage to it.

 

Why were you using R45XLS. A 1971 454 should use a R44TS according to a number of sites including AC-Delco.

 

I have a friend in Louisiana who has a 2-ton Dodge work truck. It has platinum spark plugs in it and he just told me the plugs will easily last 100,000 miles so there definitely is an advantage to running the modern platinum or iridium spark plugs. Now I just wish ignition modules would last half that long.

 

My question is, why are you replacing them in the first place? Just because of erosion?

 

Good question,......

What I have noticed is that the daily drivers some are comparing their engines with is that they last much longer than those that are monkeyed with....ie {the Vette}
Also the plug gap with whatever engine runs best at .035......if you cannot get your engine to run correctly {like new} then get a better tuner. It's not the plug whatever you use.....But in defense of the R45XLS, there are no better plugs at any price...

Spark plugs are the only way you can look inside the cylinder, learn to read them as they can thus identify engine problems short of removing the heads ,.......

 

We know the fine wire plugs fire better under extremely lean conditions of newer cars. Wondered if the fine wire would burn hotter, fire better and stay cleaner with old school set ups with performance cams, rich jetting or poor tuning??

 

I understand this

I was just curious why he was going to change his plugs (change the part number that is)

 

"Where this makes the biggest difference is in motors where the plugs are hard to get at." I run platinum NKG plugs in my 93 RX-7 cause with all of the plumbing for the twin turbos you need an arm about five feet long, two inches in diameter, with four elbow joints to reach two of the plugs. Really do not want to change them more than necessary on an engine that has an exhaust temperature about 750 degrees hotter than a piston engine. On my 68 convert, stock or platinum does not make much difference, except for the price.

 

I got my new #5305 DENSO plugs today. They come with a .040" gap but I reduced it to the usual .035" just to be safe even though I have an HEI. They are made in Japan and appear very well made. The iridium center electrode is indeed a very slim .016" diameter so I'm hoping they last as long as they claim they will; 120,000 miles! I'll install them tomorrow morning after I make a 25 mile trip to the valley to test my electric choke..

 

anyone know how much platinum is in those plugs? is there money to be made recycling them like catalytic convertors? seems to me that is the only real benefit of using them in these older ignition systems that were designed for regular plugs...

 

doesn't a stock 1971 454 use a tapered seat plug?

 

These DENSO iridium #5305's are as good looking as any of the other major brands and they're claiming a 120,000 mile life span. It'll be interesting to see how well they hold up as I pull the 10 mile long 6% grade every day.