I have been using Autolite Racing AR3934 plugs gapped at .045" per recommendation from part guy (circle track racer). I cannot hear any signs of detonation or preigntion, but I think it is running too rich.
The plugs are blackish, its kind of "baked-on" and doesn't wipe off easily. The insulator has some white on it, but is still black-ish.
Could this plug be too cold?
I am at ~3500ft elevation, running a Mighty Demon 750 with 74/83 jets.
A "racing" spark plug is too cold for the street. The heat range should be selected based on the average load the engine sees in service, not its peak power. Since street driving rarely allows full load for more than a few seconds, you have to run a fairly hot plug.
For 3500 try 72-73 and an 81. Primary jetting is the cruise setting. Go out on level country and drive 75-80 10+ miles without moving your right foot. Just get up to cruise mode and go. Then just let off and pull over some where. Pull a plug from one of the four corners because they read leaner and one from the center 4. Your really taking an average reading.
To do the secondary jetting is a WOT affair. Get the primary straight and then work on the power valve open time and at what throttle position that your secondaries open.
gkull Thanks for the tip on the jetting. The bad news however is that it looks like my driving season is over :'(. It is supposed to snow for the next week, and once that first snow hits the gravel trucks come out like gangbusters. They don't clean the gravel up here until late into June. :crazy:
My "dog legs" are already looking fairly chewed up, so I may get to go for a few more drives this year, but doubtful. The high for friday is 26, with a low of 13. It was 80!!! not 2 days ago! I need to migrate south. :yesnod:
wheelsup I can't remember now, but I think I read in the manual for my Crane ignition that .045" is a starting point. I am running a Crane Hi-6 with LX-92 coil and MSD Billet Dist. I initially had a spark problem I thought was carburation related, and it was missing at idle. The connector to the coil was bad. Got a new one from crane, soldered it in and its working well thus far. I don't believe the A Racing plugs are projected tips.
I am going to try some AC FR3LS plugs and see how they go if the snow doesn't come as expected.
I know what your saying about winter. Friday is a state holiday and a two day event at the local NHRA track. I had planned to go out but it's predicted to be in a daytime high of 44 and 20 at night.
I don't have a heater and the other depressing thing is they lumped all non- electronics 7.50 - 18.0 seconds in one bracket for a $3000 first $1200 sec. $400 each 3&4.
I'd be better off running my wife 16 second front wheel drive. Because it will do it every time. Years ago we protested that nothing over 14.50 could compete at a regular event. It's a waste of time and nobody wants to see them anyway.
Corvette Store
This spark plug heat ok for my 406?
