Curious,

I'm using 104's right now and the car is breaking up at 4-4400rpm.. which is where peak torque occurs so i have an idea that the spark is being blown out.


What gap also?

 

I am running Autolite 103's with 14 lbs of boost. They are gapped at .032.

 

ngk tr6(4177) gaped .035

 

Thanks!

These last plugs.. Autolight 103's and 104's wouldn't fire with nitrous nor would they handle this blower.

This car has a MSD 6BTM and blaster coil.. It got a fresh optispark in the past 3 months too (problem has been here all year)

It always seems to start misfiring around 4k. then starts pulling hard again.

With these 104's it pops real bad in high vaccum situations

I think i'll give the Tr6's a try.

 

BTW.. it was worse with the crane box... and way worse with the stock ignition.

 

What did the spark plugs look like when you removed them (white, melted electrode, fouled)? I'm not sure that the plugs are your problem. I've run both 104s and TR6's in my 527 rwhp 10# intercooled S-Trim and haven't had any issues with misfiring. I don't like that face that TR6's have a screw on tip, it always bugged me that they turn that's why I switched to 104s. My 104s are running hot (white) so I recently switched to 103s (2 heat ranges colder than stock). I'd check other things like wires, air/fuel ratio, fuel filter).

 

Well,

Funny you should say that.. When I finished rebuilding this motor I had a misfire/shuddering problem.. Found 2 primarys glowing at night so i replaced those plugs.

Those two plugs looked like they never fired before in thier exsistance. It was quite odd. They looked perfect, but in a bad way.

I have a feeling i must have a bad set of plugs, the car ran better with both of those plugs replaced but has had a shudder in it since day one.

I'm gongi to pull them out tomarrow for a set of NGK TR6's at .035

The last motor had roughly 10.5:1 compression with the same blower. It had autolight 103's at .032 and I believe it had the same problem just not as bad and as apparent.

 

I've run 103's for the past 2 years, all the way up to 18 psi. I'm going with a colder plug next year, a plug designed for my AFR heads. I was informed I was using the wrong plugs per a board member in a past thread.

Bill

 

well guys,

Pulled the 104's out today used TR6's gapped at .035 .. The car stopped backfiring at a cruize and idle AND the car is back to its
old part throttle 45mph wheel spinning self

BTW.. the 104's looked PERFECT.. nice color and everythign

Thanks!