Fox Spark plugs

[Mattjhop23]

Quick build
Stock bottom end 302
trickflow box r intake
harland sharp rockers
V2 on 13lbs of boost
Edelbrock rpm heads
Stock fuel
42lb injectors
Car made 520 wheel, I got it with lower intake leak fixed it. Through brand new autolite 3923 plugs in gapped to .023. Went got tuned and dyno’d very reputable performance shop here in Michigan. Been about 2 months and around 500 miles car wouldn’t start after a 200 mile cruise. Finally fired up drove home compression check, new spark plugs, spark check all good fires up perfect runs great now. Any ideas why plugs were toast already. AFR good,fuel pressure still good.
Recommendations on different plug maybe different heat range? Or more gap?
Old plugs were still gapped .022-.023 some did smell flooded or gassy

 

[FastDriver]

Fouling is usually due to too much fuel or insufficient temps.

What were your AFRs on the cruise and at idle? How rich does it swing on tip-in? It was likely too rich.

How did the shop tune your car? Are we talking just fuel pressure & base timing adjustment, or some kind of a chip? What thermostat are you running, and is the ECT coming up enough for the EEC to get to both closed loop and standard fuel tables?

3923s are the right temp range for your setup, but keep in mind that the temp range is designed to reduce detonation at WOT. Colder plugs don't stay as clean, and at street driving loads, they are more likely to foul.

The very tight plug gap doesn't help. It diminishes the spark and the temps. It could be that your ignition system is not up to handle a bigger gap, but more than likely, your tuner reduces the gap because they get fewer complaints that way.

Open the plugs up to .030-.035" and see if that causes any stumble at high RPM under load. If not, that should help with a stronger spark & more heat, which will ensure a more complete burn and hopefully reduce fouling.

 

[Mattjhop23]

Appreciate it, so gap was pretty low .024-025 AFR idle was right around 15 wot never had a hesitation and that was low 11’s I run MSD dizzy and box. So I put new plugs in and gapped them all to .023 once the engine came to temp during my cruise 10 miles ish idle was around 1500 instead of 1000. I’ll pull the plugs tomorrow and regap them little more like you stated and I’ll inspect them while I’m at it. I’m here learning as I go. Definitely good info about the spark plugs never knew that.

 

[FastDriver]

Hmm... No idea why it would idle higher after a plug change. That would be a sign of a vacuum leak or IAC incorrectly tuned. What's your TPS set to?

 

[Mattjhop23]

When I got tuned I set it to .98 haven’t touched it since. Only thing I’m going to do it change gap and see what it does maybe switch from a autolite to a ngk

 

[FastDriver]

Right on. Good luck, man.

 

[Mattjhop23]

Right on. Good luck, man.

Appreciate the reply’s I’ll change gap to what you recommended and recheck tps voltage maybe do an idle reset. Appreciate the help. I’ll update tomorrow afternoon