Archie

I've looked everywhere for these answers, someone help please.

Okay, so the owners manual says .40 gap, and gives ACDelco part # 41-103, but what is the plug temp?

On my 69 GTO the stock gap was .40, and I gapped the plugs to .45 and got an extra horse or two. Would I get any performance gain from a .45 or .47 gap and going a step hotter or colder on my Cobalt? I don't care how little.

Also, the manual doesn't say how to change the plugs. Is there any reseting of the computer, or codes that are triggered when pulling plugs and replacing or gapping?

Thanks.

Archie

19 views and no comments huh? Has anyone even gapped their own plugs?

Well I'm gonna do it this morning.

**Bump**

IonNinja

don't know what temp they should be...

as far as installation goes, u just unplug the ICM and pull the plate off then stick a long extension in there and pull em out.

I don't think there would be any harm in running a .045 gap, probably wouldn't even notice a diff...if you did it would be from the hotter plug.

Archie

Just gapped em to .45. It started right up, no codes, so now I'm off to work and I'll see how she runs. Helluva lot easier than on my 69 GTO. Time to gap plugs on GTO: 45 min. Total time on Cobalt: less than 20 minutes.

slowion2

well yeah, you don't need to index these either because of the chamber design as opposed to your goat in some views anyway. stock heat range works fine, so does one and two steps colder, but nothing thats going to give you power that you'd notice. I'm running a .035 gap for a few reasons, but I've gapped others down to that with no problems, though I woudlnt' say it really made a different IMO.

Archie

So after gapping to .45 and driving to work and back, I can tell two things.

You don't feel any difference in the stock gapped plugs, but (unless I'm crazy) I can hear the exhaust just a tiny bit different. It sounds a little bit deeper and louder between 4500 and 5000rpms (I haven't gone any higher due to only 400mi on it).

Now I don't know why it would sound any different but I am possitive it does.

Probably in a week or two I will try a hotter plug to increase spark temp over the longer arc, hopefully a couple horses.

slowion2

lol it's in your head

don't bet the house on any gain by changing the plug heat range

Red07SSNA

GM didn't just pick out a set of plugs that "might" be good for your engine. GM spent consideral time and money finding the right plug. If you were to increase compression, add a turbo, etc., then you would need to look into colder plugs, different gaps, etc.
Besides, 1-2 HP increase happens just due to outside air temp -- maybe what you hear/sense is weather related

slowion2

actually it wasn't GM but you've got the right frame of mind lol

Archie

Besides I just found out that changing plugs or gaps on plugs at home may void parts of our warranty, due to carbon buildup or oil foul.

It has been about 10 degrees cooler the past couple days. Anyways I'm regapping them to .40.