I will be firing up my new 383 soon and am not sure which plugs I need to run. It is 11.5:1 cr, AI heads, 239/245 cam, est. 425-435 rwhp.

From what I have read, I think I should go 2 heat ranges colder.

First, does this sound right for my setup?

Second, I need to know a part number for the plugs. I was looking at the NGK catalog and of course, they only list the stock replacement. I couldnt find any info on what would be a colder plug. From my searches on here, it looks like the TR55 is the stock replacement copper plug. I see others using the TR6. Is this the 2 step colder copper plug?

I really didnt want to ask the parts guys about this because I knew they would just look up the stock plug in the catalog and tell me that is the only one that will work.

thanks

 

I would like to know this also.. forgive my post, just subscribing to the thread..

 

Ussually, I can learn what I need just by reading others posts, but I couldnt really find what I was looking for. Maybe this will help some others as well.

 

Untill I read your post i hadnt even thought about it..

 

http://www.ngk.com/sparkplug411.asp

go to Numbering System at the bottom of the left-hand sidebar

In TR55, the first "5" designates the heat range..... hottest being "4" and coldest being "7". So 2 steps colder would be a TR75. You'll just have to try it and see how well it works for you. If the plug can't stay hot enough to self-clean then you'll need a hotter plug, maybe the TR65.

-Mindgame

 

Similiar set-up as me..Ive been running Autolite 104's for a while now and no problems..

Cody

 

"Rule-of-thumb" is to drop one step on the heat range for each 70HP added. I run an AutoLite 103 (2 steps colder) on a 500flywheelHP 381, when running NA. Like Mindgame said, pick a plug and see how it works in your setup. Too cold and its going to carbon up in daily driving, too hot and its going to burn up in "aggressive" driving....

 

I have been running TR55s set at .035 instead of the factory .050 and it still seems like a hot plug, the plugs stay very clean, but like they were in a blast furnace. If I go down to a TR45 should I maintain factory gap or close it as well?

 

The 0.050" factory-specified gap is suitable only for platinum plugs. If you use a non-plat plug, you should bring the gap down. How far you bring it down depends on the ignition system and the operating conditions for your engine. I run the 103's at 0.035". But on spray, I use a Champion plug a lot colder than the 103, and gap it at 0.027".

 

that link was very helpfull. It seems to have a lot more useful info than the catalog.

I think I will pick up some TR75s and see how they work.

 

If the TR55 seems "hot" and you want a cooler plug then you need to go with the TR65 or TR75. The TR45 is one step hotter. NGK's heat range designation goes from "4" being hottest to "7"... coolest.


-Mindgame

 

Thanks Mindgame and Injuneer. I was thinking the first number after the T was the heat range, so the second one is and higher number is colder, got it!!

 

Perry,

My apologies! Please go back and read my last post. I contradicted myself (I don't use the NGK plugs) and got a little dyslexic... so I edited the response. You're right, the first digit designates the heat range. Sorry about that.

-Mindgame

 

what kind of negative effects will I have by running the TR55's with the .050 gap?????