What should the plug gap be set to blower cars?

And can you gain or lose hp by it ?

 

0.035 gap for boost.

I suppose you may lose a small amount of power, but that loss is canceled out by you not getting detonation and ruining your motor .

 

At 15psi I run .025 gap. It runs great! But....they foul out every couple of months.

 

sorry to get off topic but why are your plugs fouling? gap, wrong heat range plugs, running too rich?

 

There's a lot of things that causes this for me. I run Autolite 3924(one heat range colder). First of all, the gap is much shorter than say stock, so fuel cannot burn as efficiently. Second, with 15psi boost, that force blows right past the stock rings(blowby), leading to quicker fouled plugs. Also, the plugs are not meant for boost/racing. They are a street plug, that actually work well. Plus, they only cost $13 for 8. I wish I could explain it better, but basically: street plugs + 15psi + blowby + .025 = quicker spark blowout. Also, the car does run a bit rich(purposely) to save my head gaskets.

 

May be off topic just curious. Why is the gap so much closer for boost applications than stock settings?

 

With the lower gap, the spark has to travel less which reduces spark blowout. Anytime more than 4 pounds of boost is seen in force induction engine the spark has tendency to be blown out, hence the reduced gap.