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cpetrice · 04-13-2002, 06:13 AM

I was running sf2e plugs on my car (skinny plug) and accel 8.0 mm wires,gap at .35-.40. Operating temp was around 210. I changed to sf8e plugs (fat plugs) MSD 8.8 plugs,and a .65-.70 gap. operating temp is now around 180. I thought the fatter the plug,the hotter the burn,the hotter the engine ran?!? someone set me straight here.....

cpetrice · 04-13-2002, 06:13 AM

I was running sf2e plugs on my car (skinny plug) and accel 8.0 mm wires,gap at .35-.40. Operating temp was around 210. I changed to sf8e plugs (fat plugs) MSD 8.8 plugs,and a .65-.70 gap. operating temp is now around 180. I thought the fatter the plug,the hotter the burn,the hotter the engine ran?!? someone set me straight here.....

Tom Vaught · 04-13-2002, 11:42 AM

Charles,
I do not understand your term "The fatter the plug" I have heard "cold" plug vs "hotter" plug in relation to a "Standard" heat range plug as specified by the factory, "45S" for example.
A 44S is "colder" which means that it conducts heat away from the tip of the spark plug easier.
A 46S plug is "hotter" and would do the opposite.
Different engines have different plug requirements
so a 44S plug might be "cold" on one application
and "Standard" on a second application. The spark
plug gap has an effect on the ability of the plug
to fire the mixture and also the plug temperature
of the plug. Some plugs are designed to work well at a specified gap and changing the gap will put
the plug out of its design range. It will still
work but not at the same durability or temperature
range. Tom V.

cpetrice · 04-13-2002, 02:42 PM

Tom. I was under the impression that the fat plug (larger in diameter) would burn hotter than a skinny plug (small diameter plug) so when I changed the skinny plug in my car to the fat one,I thought the temp would raise,not lower. the plugs are basically the same,same tip exposure,same length,same ceramic length,just one is "fat" and one is "skinny" so I take it that the "fat" plug is a colder plug?!?!

Gooatee · 04-13-2002, 03:40 PM

charles, are you talking about the diameter of the plug body? You may have gotten a different heat range and diameter at the same time but, that being said I cant see it making that much difference in the temp! The things that make you go hmmmmm?(lol) There is probably more going on here than meets the eye!

Tom Vaught · 04-13-2002, 05:01 PM

Charles,
Post the numbers off the two plugs on the web.
The numbers and letters should be clearly visible
on the side of the plugs. We can figure it out from there. Tom V.

cpetrice · 04-13-2002, 05:22 PM

Hello tom. The numbers where on the main post,but here they are again. "skinny" plugs,SF2e. "fat" plugs,SF8e. thanks.

455Dave · 04-13-2002, 06:36 PM

Tom and all:

Those are Splitfire numbers. If I read the chart right:

SF2E = R43TS (or R44TS)
SF8E = R47S

I'll let someone explain the difference in the plugs.

Dave(plugs is plugs)

Lando · 04-13-2002, 06:53 PM

Why did you change the plugs in the first place? Was there something wrong? Like Goatee said, I don't think just changing plugs alone would make your engine run 30 deg. cooler. Did you make any other changes?

[ April 13, 2002: Message edited by: Lando ]</p>

78 GHOST · 04-13-2002, 07:20 PM

Initial Timing???

cpetrice · 04-13-2002, 07:48 PM

other than the wires and spark plug gap,I didn't change jack. as for the plugs,I ordered 2 sets,one the 2e's,and the other 8e's. scott from summit told me the 8e's where the correct plug,so I swapped them.

455Dave · 04-13-2002, 07:58 PM

2E's are 5/8ths tapered seat plugs.

8E's are 13/16 flat washer sealed plugs.

What heads do you have?

Dave

cpetrice · 04-13-2002, 08:02 PM

I am running 670's,on a 350.

Will · 04-13-2002, 08:53 PM

The size of the plug body doesn't affect it's heat range. Heat range is affected by the length of the tip and insulator inside the threaded portion of the plug. I don't know why GM switched over to the "skinny" 5/8" plugs in the '70s (I've always heard them referred to as "peanut plugs") but it shouldn't affect the operating temperature of your vehicle.

The 8e's, being the 13/16" washered plugs are the correct style for your heads. Who knows, maybe you had a poor seal around the plugs using the 5/8" plugs in those heads? Sounds far fetched, but stranger things have happened...

cpetrice · 04-13-2002, 09:18 PM

what would loose fitting plugs do? I did have a couple that I could unscrew with my fingers.

455Dave · 04-13-2002, 09:51 PM

Dunno if it could be the leakby, but if you place the plugs side by side you should see that the electrode placement in the combustion chamber is very different. IIRC, the TS plugs seat deeper than the S plugs.

If it's running cooler, it's gotta be a bonus.

Dave

Tom Vaught · 04-14-2002, 01:25 PM

Charles,
You need the large body plugs with the washers on
your 670 heads. You also need a plug that has a heat range equivalent to a 45S Delco A/C plug.
The taper seat plug will leak at the head surface but will also NOT conduct any heat away from the the spark plug tip and to the water jacket in the head. They need to be torqued in place not over-tightened or loosely tightened. Tom V.

Brian Baker · 04-14-2002, 11:14 PM

Charles' 350 required R46S plugs stock. How the 670 heads have changed the required heat range is probably marginal at best. With premium gas, R46S or R45S will both probably work equally well.

Splifire plugs = great marketting ploy to bilk you out of money.

I tried a set in my 92 GMC when it was new. Didn't see an improvement in gas mileage and didn't feel any performance increase, but they had to be changed just as often. Switched back to standard AC plugs and have never looked back over the last 263,000 miles (but changed alot of plugs since then - LOL).

Dave A · 04-15-2002, 08:20 AM

Hmmm....30 degrees difference in coolant temp from just changing plugs??? I'd suspect something else going on, unless the old plugs were causing erratic combustion. I don't think just the heat range can really affect engine coolant temp that much.

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