which spark plugs ??? - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 07-07-2019, 03:58 AM Thread Starter
 
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which spark plugs ???

Hello guys,
I use the R45S Spark plugs at my 1968 Le Mans (400cui engine from 1970, heads: 62 from 1968, tri-power carb, Performance cam, unknown...)
I think, the spark plugs are a little too bright, and I want to use colder spark plugs, which should I buy ?
R44S, R43S ? other brand ?

regards: Peter
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post #2 of 4 (permalink) Old 07-07-2019, 09:23 AM
 
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Originally Posted by kobold View Post
Hello guys,
I use the R45S Spark plugs at my 1968 Le Mans (400cui engine from 1970, heads: 62 from 1968, tri-power carb, Performance cam, unknown...)
I think, the spark plugs are a little too bright, and I want to use colder spark plugs, which should I buy ?
R44S, R43S ? other brand ?

regards: Peter
Hmmmm. A little too "bright?" That's a new description to me.

Today's blend of gas does not produce the coloring of old. Very difficult to read plugs, so you can't really judge by the "brightness." You can go colder, but then you want to make sure you are not fouling the plug and not getting a good burn out of them.

Rather than go colder, why not go a little more on the fuel? Today's gas runs leaner that in the past, especially with the ethanol if you are using it. And a bigger cam may require more fuel as well. Factory jetting is .062 in the center carb and .068 on the outboard carbs. Jet sizes for best performance is .073 in the center and .069 on the outboard carbs. This is what was done by Milt Schornack with their Royal Bobcat package on the 1966 tri-power cars having the "ram air" hood package.

If you are not experiencing any issues like "pining" or "detonation," I would leave them alone. The R44S, as I recall another member was asking about this, are no longer made and were very expensive on Ebay. I assume there are other brands that can be cross referenced. The Champion is J12 series works and colder plug used for maximum performance at the track would be the J10.

Stay away from split fires, or the "thin" wire type plugs. Stick with a conventional type electrode.

Keep the plug gap .032"- .035" as it takes less energy to jump the gap and you get a stronger spark.
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post #3 of 4 (permalink) Old 07-08-2019, 03:34 AM Thread Starter
 
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Hello Jim,
thanks a lot for answering.
I use the "best" fuel I can get in Germany with using a lead additive.
Of course, I wouldn' use split fire spark plugs, but what about the R43S plugs ?
I read in the 1968 Pontiac Owners- Manual, they can be used in Cars/engines with Trailer or HO engines (like GTO).
These plugs are still available.
The gap of the plugs is 0.0354 (0,9mm), maybe I'll reduce it a little...

Till now, I didn't examine the carbs, (I don't know the Jet sizes...) I think they work well. Maybe I'll do this during winter time.
Regards: Peter
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post #4 of 4 (permalink) Old 07-08-2019, 05:58 PM
 
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Originally Posted by kobold View Post
Hello Jim,
thanks a lot for answering.
I use the "best" fuel I can get in Germany with using a lead additive.
Of course, I wouldn' use split fire spark plugs, but what about the R43S plugs ?
I read in the 1968 Pontiac Owners- Manual, they can be used in Cars/engines with Trailer or HO engines (like GTO).
These plugs are still available.
The gap of the plugs is 0.0354 (0,9mm), maybe I'll reduce it a little...

Till now, I didn't examine the carbs, (I don't know the Jet sizes...) I think they work well. Maybe I'll do this during winter time.
Regards: Peter

I think it was the R44S that was used in the Ram Air engines. The R43S may be suggested, especially for towing, because the engine is being worked harder and towing will cause the engine to run hot. For the HO, it might be ok to use if you were racing the car more than street driving it as my experience is that racing the engine will help in blowing out the carbon build up.

The carbon build up can cause a car to run poorly and even when these engines were newer and leaded gas was used, you occasionally had to "blow out" the carbon build up to clean out the cylinders and plugs by simply accelerating hard as you entered the highway. Had a car that was definitely over carbureted and over rich. Ran like a champ as long as I was running hard all the time. As soon as I would take it easy thinking I was saving on gas mileage, the carbon would slowly start to build up on the plugs and it ran poorly. Wind the engine out in every gear a couple times to "blow out the carbon" and it would run fantastic again. So I learned I had to run the engine hard to run it at its best. 8 miles-per-gallon was a little tough on the wallet at the time.

You can run any heat range you choose. Just monitor the plugs. The thing to look for is fouling. Once you see fouling, or carbon deposits on the plug, you know it is too cold and needs to be a hotter plug.
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