Need help tuning 302
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Trailering
Joined: Mar 2022
Posts: 16
Likes: 0
Need help tuning 302
The 302 I have is from a 1970 something f100 that was put into a 1983 ford ranger. The truck should be ready to go and drivable but the engine sounds horrible. Below I attached a video of it running.
Problems: The idle screw is at max but its still idling really low, There’s black smoke spewing from the exhaust (super rich) but the idle mixture screws are all the way in, and it has trouble revving.
What I’ve done: The engine was rebuilt last year, the carb was replaced 2 years ago (motorcraft 2b carb), distributor is new, spark plugs are new, coil is new. The engine might be cammed, but I don’t know for sure. I got the heads and cam off of a different engine from the junkyard. Timing was set a couple days ago as well. I drilled the carb jets larger on the assumption that it was cammed.
I am assuming it is fueling related due to the black smoke. Do y’all have any ideas? Any help will do
Problems: The idle screw is at max but its still idling really low, There’s black smoke spewing from the exhaust (super rich) but the idle mixture screws are all the way in, and it has trouble revving.
What I’ve done: The engine was rebuilt last year, the carb was replaced 2 years ago (motorcraft 2b carb), distributor is new, spark plugs are new, coil is new. The engine might be cammed, but I don’t know for sure. I got the heads and cam off of a different engine from the junkyard. Timing was set a couple days ago as well. I drilled the carb jets larger on the assumption that it was cammed.
I am assuming it is fueling related due to the black smoke. Do y’all have any ideas? Any help will do
Mountain Pass
Joined: Aug 2014
Posts: 162
Likes: 21
The main jets should have no effect on the idle quality since there shouldn't be any fuel moving through the main jets while idling. If the carb has been sitting for a few months before being put in to service again, I'd suggest a full carb tear down & cleaning, making sure all the ports & passages are clean & clear of blockage. Carburetors and modern ethanol added gasoline don't play well together, gaskets & accelerator pumps get damaged by the ethanol, along with gummy deposits building up on everything the fuel touches. Once you ensure the carb is reassembled correctly, do the initial bench adjustments, like the transfer slot to throttle plate gap, and for the idle mixture screws I usually start with them being around 1.5 turns out from seated.
Checking for vacuum leaks while running, carefully spray some carb cleaner around the base of the carb and the various vacuum lines to see if the idle speed changes. The fancy way to check for vacuum leaks is using an automotive smoke machine that pumps smoke in to the non-running engine (under slight pressure) and you look for smoke leaking out of any spot that there should be no leaks.
Checking for vacuum leaks while running, carefully spray some carb cleaner around the base of the carb and the various vacuum lines to see if the idle speed changes. The fancy way to check for vacuum leaks is using an automotive smoke machine that pumps smoke in to the non-running engine (under slight pressure) and you look for smoke leaking out of any spot that there should be no leaks.
Lead Driver
Joined: Sep 2003
Posts: 7,018
Likes: 210
From: SoCal
Black smoke coming out of the exhaust usually indicates too much fuel. The first thing I would check is to see if the needle valve on the fuel bowl float is working.
I haven't worked on a Ford carb in over 30 years, so I can't remember if it has a power valve like a Holley. But blown power valves is a common problem on Holleys, which allows extra fuel to get sucked into the intake manifold.
I haven't worked on a Ford carb in over 30 years, so I can't remember if it has a power valve like a Holley. But blown power valves is a common problem on Holleys, which allows extra fuel to get sucked into the intake manifold.
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