What Spark Plug gap should I go with

sdhd97 · Aug 2, 2010

Grumpy

I just bought the stock AC Delco plugs for my 87 vette. What gap should set?

383 Strocker
10.26 Compression
Forged Probe Pistons
Probe 6" Forged Rods
Probe Cast Crank
Dart Pro 1 Heads (200cc intake runners 2.02 intake 1.60 exhaust 64cc combustion chamber)
TPIS Big mouth manifold
Super Ram Plennum and Runners
Accel Cam Shaft (050" lift: 211/219 (int/exh)
Valve lift: .499"/.525" (int/exh)
RPM range: 1,000-5,800 rpm)
Crane roller Rockers.
MSD 6al and MSD Billet Distributor, wires and coil.
TPIS Headers no cat into Flow masters
Bosch 30lb Red TOP INJECTORS(fic)
TPIS Level 5 Prom
BBK 52mm Throttle Body
3:73 gears
TCI 2600 Stall

grumpyvette · Aug 2, 2010

Ive found .043-.047 works about the best, under about .037 rarely gets a good hot burn and you can get fouled plugs, over about .048 tends to promote high rpm missing with the stock ignition at times in some cars, obviously if you have a significantly upgraded ignition the gap can be larger but you rarely get much gains from doing so in any case so I tend to just go with .045, even with my MSD ignition or a vertex on my SBC or BBC engines I build

keep in mind an adjustable fuel pressure regulator, can change the effective air/fuel ratio slightly an INFRARED TEMP GUN and reading plugs, can tell you a good deal about the combustion conditions
BTW don,t forget to use ANTI SEIZE on the plug threads

always use a bit of anti-seize paste on spark plugs, threads, being used in aluminum cylinder heads even if not required and its best to remove & install them when the engines not very hot, be very careful to start threading them into the heads by hand, and don,t over tighten them as its all too easy to strip soft aluminum plug threads in aluminum cylinder heads, if you have access to a 3/8" drive inch/la torque wrench 12-13 ft lbs is about correct torque

http://garage.grumpysperformance.com/index.php?threads/installing-hard-to-access-plugs.962/