carb adjustment question, how to richen pass side
03-22-2008, 02:43 PM
#1
carb adjustment question, how to richen pass side Put a wide band O2 sensor in the driver & then passenger side exhaust (true duals). No matter what, I cannot adjust the passenger side down to 14.7:1 @ idle. What's the trick? Have tried 4 barrel & 2 barrel carbs. Have adjusted fuel plunger, as well as, fuel adjusting screw. Timing is 4 DBTDC, idle 800 RPM.
03-23-2008, 09:19 PM
#4
One carb is a Richmond 2 barrel & the other an Edlebrock (Weber) 4 barrel. I posted this in the fueling section & we found that it was an exhaust leak on the passenger side that was causing a false lean reading on that bank. So, the initial (false) problem has been diagnosed. Thank-you for the replies.
Am curious as to why more than 4 degrees. Stock timing @ idle is 4 degrees BTDC w/ vacuum advance (1970 Chevy 350). Don't have a double pumper & have gone w/ discount carbs to keep cost on the Monte parts low. It's a pleasure cruiser & is set up for decent fuel mileage w/ little power. However, may increase base timing once I have a better undertanding of your suggestion.
03-24-2008, 12:28 PM
#5
i think you need to take into account your type of ignition system and clarify how or define what you mean by timing.
Actual running ignition timing on any gasoline engine at idle is 8-14 degrees btdc.
a good example is late model mercruiser 3.0L 4 banger (boat) engines. They have a delco electronic distributor and when you disable the ignition module it doesn't provide any electronic advance; and the proper way to set ignition timing is to disable the electronic advance and set the (static) timing at idle to 2 degrees AFTER TDC. Then when you reconnect the ignition module it automatically advances and at idle you have around 12 deg BTDC. Best guess is you're supposed to disable the vacuum advance and set static timing to 4 dBTDC then when you reconnect the vacuum advance, at idle it pulls timing to 10-14 dBTDC. It all depends on the distributor and type of advance mechanism, mechanical or electronic, and electronic ignitions can vary considerably.
you need a vacuum gauge! Start messing with timing and carb settings while monitoring intake vacuum and that will help you greatly in making the correct adjustments, it may even indicate other problems which are preventing you from tuning the carb such as bad or incorrectly adjusted valves.
Actual running ignition timing on any gasoline engine at idle is 8-14 degrees btdc.
a good example is late model mercruiser 3.0L 4 banger (boat) engines. They have a delco electronic distributor and when you disable the ignition module it doesn't provide any electronic advance; and the proper way to set ignition timing is to disable the electronic advance and set the (static) timing at idle to 2 degrees AFTER TDC. Then when you reconnect the ignition module it automatically advances and at idle you have around 12 deg BTDC. Best guess is you're supposed to disable the vacuum advance and set static timing to 4 dBTDC then when you reconnect the vacuum advance, at idle it pulls timing to 10-14 dBTDC. It all depends on the distributor and type of advance mechanism, mechanical or electronic, and electronic ignitions can vary considerably.
you need a vacuum gauge! Start messing with timing and carb settings while monitoring intake vacuum and that will help you greatly in making the correct adjustments, it may even indicate other problems which are preventing you from tuning the carb such as bad or incorrectly adjusted valves.
