I have a 383 LT1 - ported heads, intake (no power adders). What spark plugs and gap should I use with this setup?

I was told to run Autolite 104 with .45 or .50 gap - I dont know anything about spark plugs but that gap sounds really large from what I always see advertised but again I just dont know.

Also, Golenengine's recommend the 103's for N/A and the 104's for supercharged motors.

What do I use?

THanks

 

the 0.050 gap called out by the factory is for emissions only. I went with a 0.035 gap myself. If I remember correctly, I am using the 104's or maybe one step colder than that.

In the research I did, there are many issues with using a hotter-than-needed plug but the only issue with a colder plug is potential fouling. Keep your cylinders clean with Sea Foam and there are no problems there.

 

Recommendation seems sort of backwards.... 104 is 1/2 to 1 step colder than the stock LT1 plug, 103 is another step colder than that. I run the 104 NA, the 103 with a 125-shot, and a very cold Champion racing plug with the 300-shot.

You'll be fine with the 104. If you get a platinum version, gap it at 0.050", for the copper version, run 0.035".

 

Sounds good. Bryan from PCMforless also recommended the 104's.

Thanks

 

ANyone have a part number for the 104's? Autolites website shows so many different kinds. Where is a good place to buy these? I see them on Amazon for like $3 a piece.

 

Never knew this, I read (somewhere lol) that a hotter plug on a higher compression engine caused fouling.

 

what is your compression ratio?

I have a similar LE2 383 and i'm thinking or running either tr6's or autolite 104's.

I have 11:1 CR

 

You have just about the same build I have... I will have 11.5:1 compression. I have absolutely no experience/knowledge of spark plugs and since there are thousands of them I have no idea which to choose. Let me know what you plan to use. So far I am finding that the 104's are the way to go.

But there are still different type of Autolite 104's... not sure which one to go with. And to me it seems like the 104's are lower down the line of Autolites spark plugs as far as technology and advancements go. Is there reason to not use their best extreme series or something higher?

 

I run NGK tr55s @ .035 at the suggestion of my tuner.

Higher compression engines risk washing out the spark so you have to drop the gap a bit.

 

Expensive plugs either have expensive alloys metals like platinum or iridium to reduce gap errosion or have marketting gimicks like multiple electrodes or something else.

The Autolite's are easy to find as a Walmart.

Why are you looking to spend big on plugs but not on important stuff?

 

Oh I have already spent big biiiiiig bucks on everything

which is why I am confused as to saving a few bucks on cheap spark plugs. Good info caprice, so it probably makes sense to go with the iridium plugs if they will be more likely to prevent gap errosion.

Also, I have seen ads and what not for pulstar spark plugs... anyone buy into those? Seems like one of those things they invent and they believe the market is over and no more need for improvements

 

should higher CR motors run colder plugs? Thats why i was thinking of running Tr6's, which i beleive are one steo colder than tr55's, which is what i always used to run on my stock lt1

 

I've been reading that higher compression, higher performance, force induction engines should run colder spark plugs to help remove heat faster... it depends on how much colder to go on your setup but I would def. like to learn more from those that know this stuff.

anyone care to enlighten some more?

 

Thread is getting really interesting, I am at 12:1 compression and running TR55's at .050. This thread may convince me to take them out and put new (different) one's in and to gap them smaller.

 

Higher compression generates higher combustion chamber temperatures. Put a "too hot" range plug in a high compression setup, and the electrodes are going to burn/erode faster. Put too cold a plug in, and the plugs will foul. The idea is to find a plug that doesn't burn electrodes and doesn't foul with carbon with excessive idling or low speed operation.

Old rule-of-thumb used to be to go one step colder with every 75HP you added. But with modern EFI engines, you can generally up that guideline to 100HP added or above.

Don't worry about how much the plug costs.... cheap is not "bad". It just means you are getting a copper core plug, and it will erode the electrodes faster than the platinum or iridium plugs. If you check and change your plugs often, you are not giving up anything by using a "cheap" copper core plug. The factory wants the plugs to last 100K miles. Most of us will want to change them before that, at the beginning of the racing season, etc.