Join Date: Aug 2001
Location: Lawrenceville, PA, USA
I pulled the plugs last night.
Plugs 5,7,6,8 all look the same:
60% Black porcelain with dark brown coloring on the other 40%, dry to "sooty" looking. The ground electrode looks white on the end, or even a light gray color.
The front plugs, 1,3,2,4 all looked the same:
Black, wet looking procelain and black ground electrode. Each of these plugs has oil on the threads too.
I just eyeballed the plugs. The engine is fresh, less than 500 miles. I am trying to get my timing curve and carb adjusted.
Why would the back plugs look different than the front?
Could a bad header gasket do this?
Bad intake gasket?
The motor has not been revved above 3500rpm's yet and has a lot of idle time on it, or tuning time revving to 3500 to check timing.
The vacuum reads 7.5 to 8 in-hg at 900 rpms. It bounces from 7.5 to 8 but steadies out at about 1200 rpms. I think the bounce is due to the cam.
The timing is currently at 12* initial and 24* total, no vacuum can hooked up.
I just bought a new set of AC 45S plugs to try.
How can I tell if I am getting detonation?
Lots of questions, but thanks for any comments.
'79 Z28, 4spd, 3.73 10 bolt, 350 4-bolt .030 over with stud kit, 10:1 Compression, Keith Black Flat Tops, Comp Cams Magnum 294 Solid Cam .525 lift, 63cc Heads, Stainless valves, hardened exhaust seats, guideplates, Summit Needle Bearing Roller Rockers 1.5 ratio, Offy Single Plane Intake, Holley 650 Vac. Secondaries, Stock HEI (for now), Headers 1 7/8" primaries, 3" Collectors into 2 1/2" exhaust with "H" pipe and Turbo Mufflers.