Can hotter spark plugs cause severe damage???

You must have mis-typed because you have shown the same NGK number.

"6" is a very reasonable NGK heat range for a 308 driven in the US. If you're (fortunate enough to be) hitting triple digit MPH speeds often and for extended periods then you'd probably want to stay with the stock "7"s.

There's no real "advantage" to heat range -- you want to use a plug that's hot enough to get to (and stay in) the self-cleaning temperature range for how you use it.

Check www.ngksparkplugs.com -- a lot of good tech info there.

 

Agree with Steve here, most of the carb 308 users have NGK "6" heat range as standard, and use the even hotter "5" if fouling is a problem. There was an article about a year or so ago in Forza, where their technical expert recommended the NGK "5" heat range as recommended in most cases.

 

christopher -- Of course, you are right that the OMs show an NGK "8" plug. I can't recall just where I'm getting the "stock is 7" recollection (might be from the NGK look up table), but I'm having a flashback that even Ferrari figured out that an "8" was just way too cold for realistic US street driving, and they went to "7". Regardless, I'd still say "6" is a good place to start if you're not going 100+ MPH frequently.

 

From what I understand about spark plugs is "hot" or "cold" has nothing to do about the plug when it's firing.

Hot means after it fires, the body of the plug remains hot for a longer period of time.

Cold means after it fires, it cools down faster than hot plugs.

What all this means is a puzzle to me!

I'm using BP7ES in my 308 right now.

 

For what it's worth, I'm using BPR6ES plugs in my 330. (They're similar to BP6ES, but are resistor plugs.)

My owner's manual suggests a gap of 0.025" for the original Marchal plugs. The plugs come gapped to 0.035", and I've always heard you don't want to change the factory gap by more than 0.008", so I set 'em to 0.027". They work great.

Also for what it's worth, the NGK heat range is the opposite of, say, the Bosch range. In Bosch terminology, a 7 is actually a hotter plug than a 6. Which makes any comarison of any heat number from one manufacturer to another pretty innaccurate.

--Matt

 

From what I understand about spark plugs is "hot" or "cold" has nothing to do about the plug when it's firing.

Hot means after it fires, the body of the plug remains hot for a longer period of time.

Cold means after it fires, it cools down faster than hot plugs.

What all this means is a puzzle to me!

I'm using BP7ES in my 308 right now.

To put it simply, a hotter plug stays hot longer in order to help burn off and deposists. Cold plugs are of course the opposite. The down side is it is all a trade off, a hot plug will stay clean, but it will be more prone to encourage detonation due to the residual heat. Not necessarily the kind that you can easily hear, but it is capable of long term damage never the less. Cold plugs on the other hand wont be as prone to cause that problem, but the trade off is, they will tend to foul easier. You just gotta find what the particular motor likes. Check the Ground electrode for signs of heat, as it is another place for detonation to be encouraged.
HTH
Kermit

 

I've got 5 rating plugs in mine and I asked the same question when I changed from the colder plugs about a year ago. The general concensus seemed to be that these are pretty low compression engines so pre-ignition shouldn't be a problem.

Certainly mine has run well withs 5's in it. Doesn't misfire, doesn't smell oily and the rear end doesn't seem to get so sooty.

 

I run NGK BP5ES also, at 110mph, thru the desert of AZ. Worked great!

Not sure how I got to it (JRV??) but I also gap to .28, by beating on them with pliers! j/k. This is inside Owner's manual recommendations. I checked.

Stock carbs/jets. Stock ignition. Many miles.

I do use a Champion spark plug gapper, in defereence do the OEM equipment.
Champion plugs are cr@p. Go NGK per Tony Palladino (Forza)

 

Well I did have some Art Car Parade spectators complain about the gas fumes when starting, but I told that grouch I wasn't turning it off unless he wanted to push start it!

He STF up!

 

These are like 8:0 pistons!

I run regular gas!

I did buy oil company stock though, to offset this $2.10/gallon situation.
Paid way more than that, in OR and CA.

We MAKE that stuff in Houston!

 

So I can run regular in my '76 308? Huh!

By the way Speedy, is your gun rack in the Toyota Pickup or the 308GTB?

(Of course I'm stereotyping and assuming everyone in Texas is required to have a gun rack in at least one car.)

 

The Euro 308 here is 9.2 High grade please... and i'll keep the additonal HP/torque ThankYouVeryMuch

 

My gun rack is mounted under the front bonnet (who needs that pesky spare and washer fluid reservoir?) It is quite useful for dealing with the beat-to-heck pickups that swoop and squat on me to see my expression and fine display of one each middle finger. Ammo tray optional, requires removal of A/C. This option only adviseable if you say "eh" after every sentence. Since my car is black the barrel soot is almost invisible on the car. Speedy might have a problem with this option. I have recommended a napalm launcher.

-Mike
Car Wars player. Geeeek!