351 carb tuning issues
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3rd Gear
Joined: May 2023
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351 carb tuning issues
Have a 351 with a brawler 750, some cheap flotek head, weiand dual plane and a set of flat tops that should have it right around 11:1. Cam is an older crane with 236/240 at .050 and .520/.526 lift. Distributor is locked at 36. Engine vacuum is at 10 at idle in gear.
For the life of me I'm an unable to lean out my idle (12.5afr) without grossly leaning out the transition. I have tried everything I can think of to no avail. I've tried smaller idle feed restrictions, different power valves(to compensate for lean transition), drilling throttle plates and even inducing a controlled vacuum leak with a fish tank bubbler valve.
I'm at a loss trying to figure this thing out. I can get everything else in the fuel curve to work for me but I can't get the idle to lean out without making it go way too lean once in the transition. There's got to be something obvious I'm missing but I'm not seeing it.
For the life of me I'm an unable to lean out my idle (12.5afr) without grossly leaning out the transition. I have tried everything I can think of to no avail. I've tried smaller idle feed restrictions, different power valves(to compensate for lean transition), drilling throttle plates and even inducing a controlled vacuum leak with a fish tank bubbler valve.
I'm at a loss trying to figure this thing out. I can get everything else in the fuel curve to work for me but I can't get the idle to lean out without making it go way too lean once in the transition. There's got to be something obvious I'm missing but I'm not seeing it.
Last edited by rpsguy; May 6, 2023 at 08:42 PM.
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3rd Gear
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They are just about completely closed right now. The only thing I've found to help was using a 10.5 power valve but that only cures the lean transition.
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3rd Gear
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Spent a couple hours this morning tinkering with this thing and seem to have it mostly figured out. Went down 3 numbers on the idle feed restrictions and toyed with opening/closing primaries and Secondaries.
Can get idle afr to around 13:1 but still have a lean spot just off idle. Was able to do all of this while maintaining a reasonable power valve at 6.5. Trying to run the 10.5 was just a bandaid for the lean transition.
One of these days all these fuel circuits will make complete sense to me and this won't be such a struggle.
Can get idle afr to around 13:1 but still have a lean spot just off idle. Was able to do all of this while maintaining a reasonable power valve at 6.5. Trying to run the 10.5 was just a bandaid for the lean transition.
One of these days all these fuel circuits will make complete sense to me and this won't be such a struggle.
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