OK today, we had a better weather day in the Pacific Northwest, not exactly sunny but it was cloudy dry and about 55 degrees.
I took this opportunity to weld in a bung in the exhaust collector for my wideband and started the tuning of my engine. Just to give an update, I'm running a Holley Street Avenger 570 CFM with a vacuum secondary, electric choke 4150 series carb. It sits on a Weiand single quad tunnel ram. Engine is a bored 283 to 301 cu in., basically a .125 over bore. Have a .450 lift cam with 224 degrees of intake duration at .050 and 230 degrees of exhaust duration at .050. Stick is setup 4 degrees advance on 110 degree lobe separation. Engine starts cold on one crank and comes up on fast idle. After it was warmed up, I set the idle mixture on all four corners of the carb for best manifold vacuum which is about 11 inches. The carb is rich on warm idle with A/Fs of about 12.5 to 1. Went for a easy cruise and main metering is also rich with A/Fs in the mid 12's holding 35 mph on level ground, I would of liked to of seen it more towards mid 14s there so I'll need to jet the main jets down (it came with 64s), then I can work on the pump shot which I changed to a 35 squirter, but it still isn't enough. The engine was popping back through the carb wit the 31's that came stock with the carb. The pop is gone but it isn't still rich enough with A/Fs going into the 15s and 16s with throttle tip in. Secondary side of the carb is totally out to lunch , extremely lean. As soon as I started to press down I could see we aren't even in the ballpark. I'll get the main jets accelerator pump done first then proceed with power mode after that. I'll need another power valve too it is a 8.5 stock, probably go with a 5.5. I don't know how anyone can tune a carb by just reading plugs, I've had this wideband for about 5 years now and it takes all the guess work out of it. Now I've seen it first hand: cold startup on the money, main metering pretty rich, pump shot very lean, power mode lean, secondaries extremely lean. I'm pretty confident though I'll get the single quad tunnel going down the road without too many issues. If anyone has any ideas please post up, I always value input and help in any way.
Thanks in advance,
Steve
I took this opportunity to weld in a bung in the exhaust collector for my wideband and started the tuning of my engine. Just to give an update, I'm running a Holley Street Avenger 570 CFM with a vacuum secondary, electric choke 4150 series carb. It sits on a Weiand single quad tunnel ram. Engine is a bored 283 to 301 cu in., basically a .125 over bore. Have a .450 lift cam with 224 degrees of intake duration at .050 and 230 degrees of exhaust duration at .050. Stick is setup 4 degrees advance on 110 degree lobe separation. Engine starts cold on one crank and comes up on fast idle. After it was warmed up, I set the idle mixture on all four corners of the carb for best manifold vacuum which is about 11 inches. The carb is rich on warm idle with A/Fs of about 12.5 to 1. Went for a easy cruise and main metering is also rich with A/Fs in the mid 12's holding 35 mph on level ground, I would of liked to of seen it more towards mid 14s there so I'll need to jet the main jets down (it came with 64s), then I can work on the pump shot which I changed to a 35 squirter, but it still isn't enough. The engine was popping back through the carb wit the 31's that came stock with the carb. The pop is gone but it isn't still rich enough with A/Fs going into the 15s and 16s with throttle tip in. Secondary side of the carb is totally out to lunch , extremely lean. As soon as I started to press down I could see we aren't even in the ballpark. I'll get the main jets accelerator pump done first then proceed with power mode after that. I'll need another power valve too it is a 8.5 stock, probably go with a 5.5. I don't know how anyone can tune a carb by just reading plugs, I've had this wideband for about 5 years now and it takes all the guess work out of it. Now I've seen it first hand: cold startup on the money, main metering pretty rich, pump shot very lean, power mode lean, secondaries extremely lean. I'm pretty confident though I'll get the single quad tunnel going down the road without too many issues. If anyone has any ideas please post up, I always value input and help in any way.
Thanks in advance,
Steve