Spark plug question--tuning

[reborn55]

Been playing with the 55 again. Figure it might be time for some tuning--was getting a bit of low rpm surge. Plugs looked real lean--so I enriched the carb a bit(Edelbrock)--made a noticeable difference. Can't remember when I last changed plugs--so it is probably time---Thinking about a heat range change maybe. I am running AC R45s plugs.

Engine is 283 bored .060, 10.5 to 1 pistons, good size cam(around 10-11 inches vacuum), Corvette power pack heads, Edelbrock intake and carb, Hedman hedders, pertronix ignition, initial timing 16 degrees, etc.--little over 300 h.p.

Have run this combo for almost 16 years now and plan to stick with it.

Any suggestions to plug or am I in a good heat range. Thanks

[wayne petty]

one thing...    they sell these or similar gauges in many parts stores and online...

http://www.summitracing.com/parts/SUN-CP8200/

200 will get you a wide band gauge..

this way.. you know what your tuning actually is..

you might be able to get the air fuel ratio dialed right in..  get better power... get better fuel economy...



many people don't know about the hidden idle transition feed restriction in the AFB/AVS style of carbs...     i would imagine that most come sized for a 350 carb... so they are lean for larger motors and rich for smaller motors..  but only an air fuel ratio gauge will tell..

seat of the pants can find large sizing problems.. as it will have a terrible unfixable bog off idle... no primary jet changes , power piston spring or needle changes will get rid of it.. as the problem happens when there is not enough air flowing through the booster venturis to pull the fuel over...

changing the idle mixture screw setting does not help much as the throttle blade has moved away from its round hole and is trying to pull fuel from the idle transition slot just above it...   and its fuel is controlled by an idle transition restriction.. that is hidden in the booster venturi assy...


i realize that this does not answer the question exactly ... but i HOPE it helps..