spark plugs and e85

I've made a lot of changes to my car this past winter, and one of the changes is e85 fuel. Although I'm not quite ready, where should I start with the spark plug heat range?
engine basics are;
- standard bore 460 with flat top pistons approx 11.5:1
- ford racing scj heads
- victor intake
- 1050 carb

Thanks!

I will be firing up my new 521 on E85 this coming Saturday and I had my carb built by Mark Sullens and he adamantly told me to use NGK R5671a-7 plugs which I believe are 2 ranges hotter than a standard plug.  I think they would be similar to an Autolite AR3935.

I had the standard AR3933 plugs in my engine waiting to go but he said that they are way too cold for E85.

For reference, my engine has the trick flow 325 heads, trick flow mafia intake, flat top pistons and should be 12.3-12.5 compression range and 760 lift cams.

I'm using NGK-8 plugs with good success. If you don't have a wide band get one. I'm at 13.5 to one. Lower compression may like a hotter plug.

A wide band is in the works...Thanks guys, at lesst I have a place to start!

I'm not sure I understand why E85 would need a plug that's any different from any other fuel. Why would it make any difference when compared to any other unleaded fuel gas or methanol?

That's the reason why I asked this question...it's unfamiliar territory for me...but I do know, different heat ranges can and will affect performance...

DaveMcLain wrote:I'm not sure I understand why E85 would need a plug that's any different from any other fuel.  Why would it make any difference when compared to any other unleaded fuel gas or methanol?

Combustion temps are lower that will lower the plugs operating temperature. Then a higher heat range can be used to get the plug temperature up to a better operating range. This is probably a small difference where one heat range different is optimum.

I have mixed beliefs on this whole hotter plug thing.
Ive seen big debates on other sites about this.
I cant argue with folks claiming to have made their motor run better and or make more power.

I have a hard time with the claims of more power though.   Heat range has to do with the plugs ability to stay clean without overheating.  Has nothing to do with spark output or intensity.  
If the spark is not strong enough then an ignition upgrade will increase power.  

I still run 1 heat range cold from stock in my low compression/nitrous combo 460 on e85.    Never a problem.
Ive run from 8-10 ngks in various n/a and turbo charged motors and never seen a difference in driveability or power.
Ive dealt with carbs that where super rich to start and through  the tuning process never even fouled a plug.  There just isnt enough hydrocarbons to dirty the plugs that bad.

I have noticed when guys are trying to lean out their cruise and they start getting misfires they aim it at plugs too cold, or just too lean, failing to realize that at leaner mixtures more timing is needed to complete combustion.

Good info...thank you!

Spark plug heat can be a weird thing. A few years ago I had a circle track customer who started having trouble with spark plugs after running the same set for over a season the year before. He races dirt so that track conditions vary a lot but if the track was really heavy "hammer down" he could burn up a plug in about four laps. If the track was normal the plugs would look perfect! Switching to a colder plug cured the problem and he was able to run those plugs for the rest of the season without attention.

The change really wasn't in the engine it was in the chassis which he worked on a lot over the winter and that allowed him to run it harder and use more power from the engine.

What was really interesting was when we ran the car with a data logger and saw the difference between what would burn up the plugs vs what wouldn't and the difference was about 1/2 second of full throttle per lap! It's like the plug was hot enough to stay clean, cold enough to not burn up most of the time until it wasn't and then it would fall off a cliff.

That 1/2 second at 7,000 rpm is only another 29 ignitions per plug but in a half second time the added heat was the factor to burn it down over a small number of lap times. Amazing!!

Some of us are expecting the plug to be perfect over a wide range of conditions that is just impossible. I thought that you should run a plug as cold heat range as cold as possible even if at low engine temperatures during warm-up and low RPM's its not happy.

I've learned that extended tip plugs that are too hot equals burnt pistons.

I plan on using the innovate LC2 wideband, It has the capability of data logging...it will be a valuable too while figuring out the tune on this new combo...

yup. Wideband is a necessity in my opinion. Absolute must for street driveability and working out transition circuits. And gets you real close for WOT hits before going to the track and wringing all the power out of it.

Still cant believe how many people show up at the track and their shit wont even make it down the track or hardly drive through the pits.

Sorry, rant.

I know what you mean, I'm passing up a track rental date with a group I run with...I didn't want to spend the money not being certain that this thing would even be able to make it down the track...I plan on nailing down the majority of the tune on the street