Hey guys, I know there are a LOT of carburetor question posts on here, I've read through quite a few, but didn't find any of the info helpful. So, here's my question...

I've just bough a '79 F150 4x4 LWB 4spd std, in which someone stuck a slightly built 302. As far as I can tell, it's got a stock cam, had long-tube headers (at the expense of non-functioning 4wd), an Edelbrock Performer 4bbl intake, aluminum carb spacer, stock cam... and a Holley 4160 or 4165. My problem is that the former owner didn't seem to want to fix any of the issues with the truck as long as it was running and the carb seems to be one of them. He most likely got the carb used, so I don't know how old it is, despite having "decoded" the date code stamp, just that it's no newer than 1997 model. Anyway, when starting the truck, choke open, I can't touch the accelerator until the engine is up and running for at least 30 seconds or it will flood. The engine catches, then runs around 200-300 RPM, then slowly creeps up to 600 RPM. I have to let it sit at 600 for a bit before revving, and when I do, I have to be very careful about it. THe plugs all show signs of running rich, as does the undercarriage of the truck and black exhaust so I suspect it's been running rich for a while. I haven't disassembled the carb yet, so I don't know what jets are in it, but do plan on rebuilding it.
I'm wondering which jets I should install to make it all run more lean. I plan on using the truck mainly for around-town and weekly off-roading. Based on the truck's weight, not much above stock if at all and the relatively tame engine, what would be a good jet size for this carb? Oh yeah, it does have a lift and slightly taller, wider tires over stock, can't remember the exact size nothing huge, about the same height as a 31 10.50, maybe 1-2" taller and 2-4" wider. Dunno how much that matters, but there it is anyway.

 

what is the model number on the carb

 

The choke and fast idle aren't connected or working properly.

Josh

 

I'd start with a complete rebuild.

However, my holley behind my 66 mustang is a 600 cfm running 66 primary jets...I experimented with 68's and it ran too rich. I'm running a small b303 roller cam behind a 5.0 with aluminum gt40y heads making about 325 flywheel...so if I had to guess you'll need 66's or smaller for your primary jets..

as well, while you're in there, replace the power valve. In screws right into the front metering plate, and if it's blown, which is very likely it will cause you to run rich. I'm pretty sure the correct procedure is to check how much vacuum you have at idle, then half that # is the power valve you want. Since you have the stock cam, you should be putting out 19 pounds of vacuum or so, so you'll want around a 9.5 power valve.

Check the float bowl settings by the weep hole in the sides of the float bowl. Adjust the float setting until it is at the view hole height. Finally, adjust the idle screws....if they're out too far it'll cause you to run rich too.

 

Fisrt, get the LIST # off the air horn and get a HOLLEY kit for it, it will have the new bowl gaskets, accelerator pump diaphram, and power valves for that particular carb. Holley jjet's the carbs prety close out the box, a hair sometimes rich but not much. At sea level, so much air requires so much gas.

Also check to se what jets are in front, and make sure they are the orioginal ones specified by Holley for that carb, and you should be able to get that truck running much better before you even start to think about changing jets.

Back fires will also blow a power valve diaphram if the carb doesn'ty have the new anti back fire modification that consist of a ball and spring in a hole. Holley carbs will run over rich if the diaphram in the power valve is ruptured and they'll run rich if the float is set too high.

The Holly kit will come with good instructions, but not the jet specs for your carb .... check Holley's online site for specs once you know the List #.

http://www.holley.com/

http://www.holley.com/TechService/Instructions.asp