What plugs to run in blown stroker?

[sugaryuk]

My Vega’s been running a bit crappy so I thought I’d try changing the plugs out. Basic specs are: 383 stroker, 671 blower, dual Holley 750 blower carbs, isky blower cam, msd electronic ignitioin. Motor is not hi-compression, revs are kept under 6k and blower is putting out around 4-6 lbs. Car is mainly driven as a cruiser with the odd trip to “Mexico”. Motor tends to run on the hotter side. Current plugs are Autolite 3924-gapped at .040”. I did a bit of research and found few sites recommending Autolite 3910x plugs—these are classed as race plugs, would they be too much for a street car? Can someone recommend a better plug and what to gap it at?

[MonzaRacer]

I really hate Autolites, I prefer AC Delco or NGK or Den so. On AC if you think the plugs is too hot look for bubbling on ground strap. On others look for silver flecks on ceramic.
Been using AC on many nitrous tunes. Show bubbling on ground straps easier.
Always use antiseize also.

[Smiley]

Did it run ok before ?
Pull the plugs and look at the tips and the insulators.
What heads are you running ? There are several different types of heads for a SBC each takes its own plug style,
The engine coolant temp is not really why you use hotter or cooler heat range plugs.
some good plug info:
http://www.ngksparkplugs.com/docs/tech/Racing_Spark_Plugs_Performance_Applications.pdf

[monzabug350]

Did you build the eng or did a shop/pro? If a shop talk to them about your problem and see what they say.Or if you did it yourself,how long have the plugs been in the eng? What do they look like when you pull them,sooty,wet,black,tan,gray,white,etc? How often do you drive the car and how far? And do you now and then "blow the carbon out"? I would not use race plugs they are usually too cold for a street eng. Have you tried stepping down a jet size or two to see if that helps? What brand/grade of gas do you run? Any additive and octane booster? Do you buy you gas from the same place or when you see the gauge on E? If the car sits up for an extended time do you put a fuel stableizer (?) in the tank? (Bad gas will give you fits) Just some thoughts.

[sugaryuk]

Turns out the plugs weren't the problem, one of the wires was. The boot on #5 which was wrapped in header tape (due to header clearance heat) was actually almost totally disintegrated. I had assumed that they were all in the same "new" shape, motor only has 2k on it---apparently they weren't. Anyways I had already bought the 3910x's so I threw them in to see how they'd do-- worked great for about 20 minutes until I snapped my crank -- see my post in the general section