Since it looks like you have a good ignition in your car, I imagine that you can open up the gap to .045 to .055 inches. As for the question of which plug to use, that really depends on how it's running. Once you stray from stock, the rules all change. I'd say stick with the Corvette spec. One thing you should remember: You'll want to use a .015" steel head gasket from GM for the 305 TPI application. if you pick a thicker gasket, you'll lose compression ratio. The aluminum head will enable you to crank up the compression ratio as high as you can. With a 58cc chamber and a .025 deck height, you'll be sitting at 9.6:1 compression ratio when you use the steel head gasket. The aluminum head can easily support a 10:1 c.r. in that 305 as long as you use 92 octane fuel.
I don't know what the torque specs are. In the 18 years of fooling around with cars, I've always just cinched them down until they make contact, then give them another 15 - 30 degrees. I'd estimate about 15 ft.lbs of torque, max. I've never lost one or busted one off!
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Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Turbine Technologies 2500 stall converter, underdrive pulleys, Crane Hi-6 & more.
1.05g skidpad verified.
New best E/T! 14.039 at 100.82 MPH in 41 degree air at Stanton, Michigan.
[This message has been edited by ws6transam (edited February 17, 2001).]