not sure whats up but I seem to have rich idle and very muddy throttle response when 302 is up to running temp, mild 302 w/ xe262 cam, ported heads, stealth intake and an autolite 4100. not sure what else to adjust almost thinking on going back to a 2 barrel set up for consistency. not real concerned with high end performance just want to to run proper at all temperatures. thoughts.
When you tuned the carburetor was the engine at normal operating temperature? What jets are you running? 4100 is a very good carburetor.
That's the thing it never really did tune out properly I mean its off not just the little bit from a cold tuning. its like the power valve is hanging open or something. its weird. but idles ok not horrible its tolerable but when you snap the gas get light black puffs out the pipes and the response is very muddy. I think there are #48F main jets in there. and I have the accelerator pump adjusted 1 leaner than the recommended placement. I do know this carb originally was on a 428 bird but yet it is a small bore 4100 has 1.08 bores. could the idle fuel passages be larger or something on one made for a bigblock?
Is this based on the OE part #? 888-465-5395 Holley remand service can tell you what the original jet size is and all the original specifications. It’s 480 CFM it looks like. You can add a 2 stage power valve by using a larger power valve cover from a 2100/2150 that has a 2 stage power valve. If it was me I would set a baseline. Check timing at normal operating temperature, make sure the 4100 is set correctly with factory specifications. What does muddy mean? Does it smell rich or like gas? Cars without a cat will have a slight gas smell from unburned gas. 4100 are very simple. The power valve and accelerator pump can easily be replaced if there is any hesitation.
muddy meaning rich.. when it idles its ok only mild rich but when you hit the gas is pretty black coming out the pipes and the response is not crisp. very sluggish responding not from lean condition either. the only way I can describe it is muddy. the main jet is original ford autolite #48F coincidentally that is the same as the original 2barrel that came off also 1.08 bore and it had #48F's I don't think holley jetting will fit these carbs? if so that opens up more options.
My main thought is that you have the timing misadjusted for your combination of parts. What's the timing curve look like? Posting your initial and total timing numbers @rpm will help us to better help you. All the time spent tuning a carb will have you chasing your tail in circles if the disty's advance curve isn't properly calibrated. The reason for this is that ignition advance has the affect of richening and leaning out the fuel curve as more or less fuel is burned in relationship to spark lead. Also.. dual stage power valves are not performance oriented parts and you'll waste your time installing one in a performance oriented environment. I have hoarded a small bin full of those types of factory parts. Don't know why since I'll never use them anyways. PS. Tossing the 2 barrel back on just for the sake of dumbing the process down will not save you from putting in the tuning time. Once you install aftermarket cams and other supporting parts?.. the factory calibrations go right out the window. No shortcuts allowed at this juncture.
the tag on the carb is C5SF-xxx cant remember the rest was told it came off a 428bird. the mains are definitely stamped 48F which I thought was ok considering the factory 2barrel has 48s. plugs are definitely reading rich as well dark brown with heavy soot building up after only short hard drive and a bit of idling time. as for timing curve I am not sure have the base line set at 10 or 12 degrees (cant remember) now. I did notice the vacuum reading was 13" + or - 2" consistent wobble so also wondering if I have an intake valve hanging open or something. I will investigate further with all advice further once our winter finally leaves..
