Spark plug gapping

[collins_dan]

I'm considering going back to NGK BP6ES spark plugs. My current plugs were installed when the engine was rebuilt and the car was set up too lean. I've enriched the mixture, which has helped at WOT, but is fouling the plugs if I spend too much time at idle, or waiting around for my run at autocross, which is this weekend. I am waiting for some new Stromberg needles to arrive from the UK, which should help out in the long run, but am considering installing the BP6ES's for this weekend. They appear to have been gapped at the factory at .03 and I was considering leaving them at that as I have a Pertronix Ignitor electronic ignition and Flamethrower coil. Thoughts? What difference does the gap size have on the engine's performance? Thanks, Dan

[m750rider]

I use NGK BP6ES as set up and gapped from the factory and they work fine with an older Lucas Lumenition electronic ignition system. New plugs will get you through a weekend just fine, but if your plugs are fouling with excessive idle time, you are still adjusted too rich. Are your needles set correctly?

BTW my car is a 69 S4 with stage II cams and Sprint valves.

[collins_dan]

The needles are set the best they can be, they are just not the right needles. They are the original fixed B1G stromberg needles, which will either too rich at idle or too lean at WOT. I am changing to adjustable B1BT, which should address the issue. They run leaner at idle and richer at WOT. I recently discovered that I have L2 cams and am currently running 15 degrees advance with standard S4 federal distributor. Once I have the new needles in, then I can play around with mixture and advance until I get it just right. Thanks. Dan

[m750rider]

Dan

I use B1Y needles, which according to Dave Bean, provide a mild power increase over the B1G, leaner at idle and richer at full throttle. They are non-adjustable, but I have found that they can be set too high in the seat and will let the engine run very rich. On mine, and I live in NC at elevation 2300', the shoulder of the needle mount is about in line with the face of the slide. A small amount of movement upwards can make a difference on needle position in the jet and will change the fuel mixture.

Bob