hello guys, i've gotten my truck up and running... sorta. I believe my friend damaged the spark plugs while he was trying to gap them. No biggie. I didnt run the truck, knew there was an issue when the a couple of the exhaust ports weren't very hot.

I did a 408 conversion, and running aluminum heads now. I got a couple of ideas im working on.

- Replace gas in tank (the truck sat for 8 months with half a tank).
- Run high octane gas. Stock compression is around 9, i should have 10 or close to 11. I have aluminum heads and a 408 crank.

The instruction sheet that came with the edelbrock aluminum heads said to use Champion RC-12YC or equivalent. However they are assuming you have a stock engine, the only thing stock is my block...

I am gonna pick up a some spark plugs tomorrow, but i talked to a few tuner guys and they suggested i run cooler plugs and maybe dial back the gap a bit because of the higher compression.

Right now when idling the truck is fine, under load i can baby it to the speed limit with no problems if i quickly accelerate and push it past 2500 it rattles a bit and knocking gets louder. I know the plugs were damaged, the porcelain tips were effected... My friend had good intentions...

I searched for a bit on these forums before asking... i wanted to ask ppl who had direct knowledge of a situation similar to mine. I like to know what guys are running aluminum heads and if they are using champion or the autolites. If you are using the autolites which series.

I was told because of the higher compression the cylinder is gonna run a bit hotter and i should probably use a cooler plug. Just wondering how cool i should be going with. Correct me if i am wrong, but Autolite 3923 is standard placement for stock? 3922 is a bit cooler?

I believe .035" is stock, what do guys here with aluminum heads run for gaps? I'd rather get your guys advice on plugs and know what im asking for before i ask a 18 year-old kid who could care less what is best for my truck.

Cheers!

 

autolite 3923 is one heat range colder than the stock champion rc12yc.

 

Thanks for that clarification. Now should i go with the 3923 or go straight to the 3922 because i have a lot of compression in the engine now.

i have done some searching around the internet as well and found several articles from the autolite website. I will list the URL's below if anyone else finds this thread from the search option.

Autolite Spark plug Technical page

Autolite Spark plug - Understanding Heat Range

Autolite Spark plug - Numbering system

 

Autolite 3924 is stock equivalant.

 

there cheap...buy them all and try them.

with a 408 you shouldnt take somebodys word for it...try them all and use the one that works best for you.

i only have a 318 but lots of top end work. heads, decked block...whole nine. i run ngk v plugs with a .030 due to the deck.

i tried all of the autolites...but still like the ngk.

 

What is "alot of compression"? 12to1? 15to1? Plug gap has to do with ignition mainly. Meaning, how much gap can you have and not lose spark energy. Also clearance in the head will be a factor too. Are you planning on indexing the plugs? And, I agree with Alabama, what plugs will be trial and error. These Magnums are finicky with plugs.

 

OK Ive got to ask..
I have also been told by a tuner guy that I needed to run one point cooler...
The parts stores cant look crap up no more , could not even find me a cooler plug, what happened to cross ref catologs.. any ways.. I see your post that "autolite 3923 is a point cooler , Thanks for that info,,

OK . I just read this: Cold plugs have a shorter insulator nose which minimises the amount of surface area exposed to the combustion gases. This means that the heat has less distance to travel out of the plug to the cylinder head. The colder the plug, the more heat it can channel out of the combustion chamber. A colder plug is necessary to handle the extreme temperatures in engines operating at higher RPMs (eg race cars) or heavy duty applications.

BUT .. : why have we been told to run a point cooler, wont that make our mpg go to poop? less combustion in the chamber??

I must also add, that I have NEVER ran my trucks rpm over 3500.. and probly not even that hi passing on the hwy,

 

Colder plug removes more heat, higher compression generates more heat..... running a colder plug is more to control detonation (spark knock) than much else. Shouldn't effect fuel economy at all.