Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - 1955 Pontiac (advice for setting efficient but driveable mixture?)

slownugly · 03-17-2014, 02:12 PM

Personally I would adjust carb, points, ignition timing to stock for the trip. I wouldn't risk doing damage.

However when you get it home then I would have some fun. I'm on the same page I'm building a 68 rambler American and I can't wait to start playing around with the carb for fuel economy.

Couple notes-
Don't waste money on a 30 dollar afr gauge. They only come with the gauge and are made to wire into the signal wire of a narrow band o2 sensor. Get a good wideband afr gauge that comes with the o2 sensor.

Invest in a vaccum gauge first!

On my car not only am I planning on messing with the carb but the entire fuel system. I ditched the mechanical pump and I'm running an electric with a relay system grounded by an oil pressure safety switch (much like gms of the late 80s early 90s) if I shut the engine off for engine off coasting the pump will shut off. Im also running a fuel pressure regulator. I'm going to set the float to factory spec but I'm going to play with pressure at the carb. Im not counting on that making a difference at all but who knows. It's a carter yf 1 barrel.

Edit: also your only going to see gains from playing with jets rather than idle mixture screws. the idle mixture circuit isnt even used at cruise speed which is where you want your lean condition. the main jet circuit is what you want to modify. only problem with that is your timing curve is set at a certain spot and guess what, if you jet it wayyy lean your going to deal with detonation and chance melting a piston or 8. msd makes an adjustable timing knob where you can retard your timing up to 15 degrees on the fly. it requires driver feedback and constant monitoring but i think it would be fun as heck to have lean burn in a carbed car!! i should pm pgfpro about it he could give some insight on timing a lean burn car.

Also I'm ditching points. I'm 25 and I know how to set these cars up but I really want to take advantage of a stronger spark if I can get it, so I opted for the pertronix conversion. Oh yea and reliability and not having to change them after 20k will be nice too

Take that mechanical fan off and toss an electric fan on via a switch or thermostatically controlled switch. I'm running an adjustable thermo switch.

03-17-2014, 02:12 PM	#14 (permalink)
slownugly Burn lean and prosper\\// Join Date: Jul 2012 Location: scranton pa Posts: 576 VLX - '93 Honda Civic VLX Team Honda 90 day: 51.1 mpg (US) Thanks: 55 Thanked 65 Times in 54 Posts	Personally I would adjust carb, points, ignition timing to stock for the trip. I wouldn't risk doing damage. However when you get it home then I would have some fun. I'm on the same page I'm building a 68 rambler American and I can't wait to start playing around with the carb for fuel economy. Couple notes- Don't waste money on a 30 dollar afr gauge. They only come with the gauge and are made to wire into the signal wire of a narrow band o2 sensor. Get a good wideband afr gauge that comes with the o2 sensor. Invest in a vaccum gauge first! On my car not only am I planning on messing with the carb but the entire fuel system. I ditched the mechanical pump and I'm running an electric with a relay system grounded by an oil pressure safety switch (much like gms of the late 80s early 90s) if I shut the engine off for engine off coasting the pump will shut off. Im also running a fuel pressure regulator. I'm going to set the float to factory spec but I'm going to play with pressure at the carb. Im not counting on that making a difference at all but who knows. It's a carter yf 1 barrel. Edit: also your only going to see gains from playing with jets rather than idle mixture screws. the idle mixture circuit isnt even used at cruise speed which is where you want your lean condition. the main jet circuit is what you want to modify. only problem with that is your timing curve is set at a certain spot and guess what, if you jet it wayyy lean your going to deal with detonation and chance melting a piston or 8. msd makes an adjustable timing knob where you can retard your timing up to 15 degrees on the fly. it requires driver feedback and constant monitoring but i think it would be fun as heck to have lean burn in a carbed car!! i should pm pgfpro about it he could give some insight on timing a lean burn car. Also I'm ditching points. I'm 25 and I know how to set these cars up but I really want to take advantage of a stronger spark if I can get it, so I opted for the pertronix conversion. Oh yea and reliability and not having to change them after 20k will be nice too Take that mechanical fan off and toss an electric fan on via a switch or thermostatically controlled switch. I'm running an adjustable thermo switch. __________________ Burn lean and prosper \\ // Last edited by slownugly; 03-17-2014 at 05:21 PM..