Spark plugs for 14:1 and E85

[98TransAmWs-6]

So I am building a 396 that will have a compression of 14.1 to 1 and will be using E85. Should I go with a cooler spark plug like the NGK 5820 which is a heat range of 10 made for 14:1 compression. At the same time e85 has cooling properties so I don't know if that counteracts the need for a cooler plug. Also would MSD spark plug wires handle that compression as well?

[2002ssslp]

With that high compression rate you will have to try several different heat ranges until you find the plugs your engine likes. 14:1 is a touchy high range and timing, detonation and heat are all going to play into your plug choice.

[98TransAmWs-6]

With that high compression rate you will have to try several different heat ranges until you find the plugs your engine likes. 14:1 is a touchy high range and timing, detonation and heat are all going to play into your plug choice.

There are like a million spark plugs to choose from which makes just trying them out expensive and difficult. How will I know which one the engine likes best?

[Firebirdjones]

Several hours in a dyno cell

[98TransAmWs-6]

Is stock a heat range of 7? If so I'll probably try 7 up to 10 heat ranges and see if performance differs any.

Edit: Nevermind, I found it. They are heat range 5 stock.

[2002ssslp]

Is stock a heat range of 7? If so I'll probably try 7 up to 10 heat ranges and see if performance differs any.

Edit: Nevermind, I found it. They are heat range 5 stock.

I would start two heat ranges colder. While the E85 will run cooler the 14:1 CR is a killer so two ranges colder may be right on the money. You may also have to open the gap a few thousandths and be very careful with the timing and listen for detonation which could kill your engine. Good luck.

[Firebirdjones]

Is stock a heat range of 7? If so I'll probably try 7 up to 10 heat ranges and see if performance differs any.
Edit: Nevermind, I found it. They are heat range 5 stock.

The only way to tell that would be in a dyno cell where you could monitor EGT's and AFR's. You won't find anything on the street by the seat of your pants, and the only tell tail sign that you went too cold would be a fouled plug. Or possibly alot of seat time at the dragstrip providing you keep track of the DA and wind conditions, but that's going to be difficult at best when trying to document spark plug changes with a simple heat range change.

We experimented with heat ranges years back in a dyno cell, and just to let you know, we found no measurable difference with NGK plugs, and this really turned me off these plugs completely. Not to mention heat range numbers are completely backwards on these plugs verses conventional thinking and every other spark plug out there. However we did find the Autolites affected EGT's and AFR's slightly when swapping heat ranges. The plugs do what they are supposed to do, so I've stuck with Autolites ever since.
If you really want to find what works best and how it affects the tune you'll need some dyno time before you stick the engine in the car. Otherwise it's going to be a crap shoot that starts off with a guesstimate.

[98TransAmWs-6]

I am not bent on using NGK so I don't mind checking this out with Autolite as well. I guess I'll have to find a place with a dyno cell not until my engine is built obviously, I don't want to run the wrong plugs and it messes up my newly built engine lol.

[Firebirdjones]

Don't know if there is really a "wrong" plug to run per say, and what ever brand you prefer, then go with it if it makes you comfortable. Plenty of people seem to run NGK's with success.

I don't build anything with E85, no availability out here, and lack of interest, so I don't have a heat range recommendation to start with. Might want to check around shops in the midwestern corn states where that fuel is more plentifull.

[98TransAmWs-6]

Don't know if there is really a "wrong" plug to run per say, and what ever brand you prefer, then go with it if it makes you comfortable. Plenty of people seem to run NGK's with success.

I don't build anything with E85, no availability out here, and lack of interest, so I don't have a heat range recommendation to start with. Might want to check around shops in the midwestern corn states where that fuel is more plentifull.

Okay I was under the impression with that high of compression the spark plug was vital because it could increase the chances of detonation if too hot. If that isn't true then that changes things but I will most likely still find a dyno cell to find the appropriate plug to use. I personally like both NGK and Autolite I have yet to see a difference in either performance wise but I have not had any engine on a dyno cell to see the difference that might find.

[Firebirdjones]

That's not what I meant.

Higher compression/cylinder pressure can and will likely require a colder plug. I drop 1 or 2 heat ranges on every engine, even with stockish compression ratios just because of the crap gas we have now. Plus I tune for max performance so I have timing on the edge, with a slight rich fudge factor on AFR, plus the cooler plugs, both to help fight detonation.

So I follow the cooler plug regiman on everything.

What I meant with yours, and what throws a curve ball in the works, is the E85 you're running. With that much alcohol in the mix, which has a tremendous cooling factor, I wouldn't know exactly which heat range would be best for that setup. If I had to guess I'd start with a step colder, see what the plugs look like and either tune for it, or change heat ranges up or down.

[98TransAmWs-6]

That's not what I meant.

Higher compression/cylinder pressure can and will likely require a colder plug. I drop 1 or 2 heat ranges on every engine, even with stockish compression ratios just because of the crap gas we have now. Plus I tune for max performance so I have timing on the edge, with a slight rich fudge factor on AFR, plus the cooler plugs, both to help fight detonation.

So I follow the cooler plug regiman on everything.

What I meant with yours, and what throws a curve ball in the works, is the E85 you're running. With that much alcohol in the mix, which has a tremendous cooling factor, I wouldn't know exactly which heat range would be best for that setup. If I had to guess I'd start with a step colder, see what the plugs look like and either tune for it, or change heat ranges up or down.

Ah okay that makes more sense. How would the plug look if it is too cold versus being too hot? I imagine too hot would be fouled but how would a too cold look?

[35th-ANV-SS]

I used Autolites and had issues. Went with NGK's.

[98TransAmWs-6]

I used Autolites and had issues. Went with NGK's.

What issues, care to elaborate?

[Firebirdjones]

Ah okay that makes more sense. How would the plug look if it is too cold versus being too hot? I imagine too hot would be fouled but how would a too cold look?

Too cold could possibly foul with gas, would be black in color. So if your AFR is pretty close and plugs are still black, I'd jump up a heat range. If the AFR is pig rich correct that first.

A hot plug won't necessarily cause problems other than possible detonation if tuned on the edge. If you suspect detonation you can usually read it on the plug long before it's audible, in which case you would see black specs (called "peppering the plug") on the white porcelen. Those black specs are actually tiny flakes of aluminum from the piston top.

[35th-ANV-SS]

I used Autolites and had issues. Went with NGK's.

What issues, care to elaborate?

They were not recommended with FI, even their cooler plug equivalent to NGK. I could be wrong, but I believe Steve was the one who found them to be problematic as they were already installed in the car before he tuned it. The car was all over the map at idle with them installed, but ran fine at WOT. Put in new NGK's and the car ran fine.

[SMWS6TA]

Are you running TR6's or 5's Jon

[98TransAmWs-6]

Are you running TR6's or 5's Jon

I would guess at least TR6 since tr5s are stock replacement plugs.

[35th-ANV-SS]

TR6's - I believe they are 2 steps cooler though.

[98TransAmWs-6]

TR6's - I believe they are 2 steps cooler though.

1 step.