Lotus76

I am looking for advice on new spark plugs.

I currently run Bosh 4008 Double Platinum plugs and fire them through a DUI (Davis unified ignition) distributor in my slightly modified 1976 L48 (heads, intake, cam, carb) with original 35 year old short block.

Its time for new plugs, I have been happy with the double platinums but over time they do have some build up.

I am looking for advise about Iridium plugs.

Good? Bad? Better? what brands are best?

or should I stick to Platinums?

Thanks John

qwank

I find the stock ACDelco plugs work the best in GM cars, and that goes for all year makes and models

c31980

best thing is follow your head manufacturer specs plug recomandation

SanDiegoPaul

noonie

The biggest advantage to those pricey plugs is their longevity.
Major BS on some new engines just to change the plugs.
Your current plugs are fine, if you're happy with them.

SanDiegoPaul

If you're driving a modern fuel injected vehicle that is designed to go many tens of thousands of miles between services, then these types of plugs make sense. Our c3 engines certainly do not fall into this category

Jeff_Keryk

Cheapo Autolites ROCK!

SanDiegoPaul

I respectfully disagree. Not on engines with a lot of miles on them or any car with carburetor

Lotus76

ttt

rcread

One of the benefits of owning the car that you do is that there is no disadvantage whatsoever in running an inexpensive spark plug. I concur with the AC Delco or Autolite selections.

birdsmith

I have seen direct side-to-side dyno comparisons from an engine builder that I know (as opposed to a magazine article where the plug manufacturer had purchased advertising) proving that there is virtually no measurable difference between cheapo run-of-the-mill AC or Autolite plugs and the super hi-dooda-dooda plugs used by NASA on the Space Shuttle. Of course these comparisons were done on low-tech pushrod carbureted engines, but honestly the best thing you can do for an old, low-tech carbureted car's ignition system is install an MSD box, add a good set of wires, and then index the cheapo plugs. Spending all that $$$ for superheterodyne unobtanium filament plugs is just a waste unless you're the guy at the parts counter selling them. If you don't want to contaminate your Vette's original underhood look, install a Pertronix. The AC plugs in my Pertronix-equipped C3 currently have 30,000 miles on them and the car's perfectly happy.

gkull

My heads use the flat gasket 14mm .750 deep reach plugs. Summit Racing did not have the autolite Iridium plugs in stock at the counter so I bought the double plantinum 3924

My ignition would eat common plugs for lunch. I pulled my common plugs once to look at the jetting and the center electrode was rounded and erroded away to where the gap was near .080. It still seemed to run fine.

I'd like to find a multi tipped or side ways jumping spark plugs

noonie

Yep, 1 hp when new if you're lucky is about all the difference, even with the super expensive Pulsar plugs.



The fancy metals just wear less, and wear leads to misfire, whether detected or not.
Back in the early 70's I tried NGK palladium in motorcycles, didn't seem to make much of a difference over oem. This stuff has been around forever.
Today, I use the cheapy Autolites in my modern FI engine but change them regularly. Iridium in my wife's hard to get to engine.

Denso makes the GM Irridium plugs, Autolite and Champion make most of the ACDelco plugs since Delco hasn't made their own in many years, Autolite makes the splitfires and so on.
Brand recognition is almost a thing of the past.
Anyone know what the AC in ACDelco stands for?

mbeeman350

[QUOTE Anyone know what the AC in AC Delco stands for?[/QUOTE]

Albert Champion
Started AC after he was displaced from an earlier company he founded Champion Spark Plugs

Paul L

Albert Champion
Started AC after he was displaced from an earlier company he founded Champion Spark Plugs[/QUOTE]

Interesting trivia! So Champion now makes Delco plugs!!

I get by with Delco R45TS very well with stock points, condensor, coil, etc. (1974 L-48).

spinadog

Keeping the trivia theme; photo I took of a Champion plug on an old piece of farm equipment located on the Channel Islands, off the coast of Southern California - thought you might want a look.

Lotus76

Thanks for everyone’s input.

I was not really looking for power gains. Although longer life would be a nice thing.

I was more concerned about keeping the plug clean and not fouled. I mentioned this was a original short block (never rebuilt) so I do get a little build up on the plugs over time.

I have seen demos (plug manufactures) that clams a stronger spark, less prone to foul or build up.

So I am asking the forum members for their advise about the platinum or Iridium plugs from that perspective.

Thanks John

MotorHead

I always thought the fancy plugs were used in newer cars because they last longer. Some of these cars you have to use a trained monkey or take half the motor apart to be able to reach them to change them

boltnut

i thought the platinum plugs run hotter so they are self cleaning....thats why they have a longer interval for changes. not needed or wanted in most of our older cars. sometimes the reach is all wrong on them too. can cause all sorts of pre-ignition with glo-plug syndrome ?

i was always told they are a big NO-NO on most carb cars....JMO

jackson