Resurgence of a F100
- Thread starter 6speedsd
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6speedsd
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Where in TN?
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6speedsd
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So, now this bich is loading up at idle. It seems to be running much better lately for some reason (I've done nothing to it), although it definitely falls on its face briefly when it shifts to 2nd. But if it idles for a bit, like if I'm at a long traffic light, it'll start getting a choppier idle and start smelling rich after a minute.
I've been doing a lot of reading on extended carb adjustments/tuning. Things like adjusting primary butterfly, changing power valves, ect. Just don't understand why it's overfueling at idle though. Changing jets won't correct that at all, so I don't think that's an issue. I've already adjusted idle mix screws for maximum vacuum, so those are close.
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I've been doing a lot of reading on extended carb adjustments/tuning. Things like adjusting primary butterfly, changing power valves, ect. Just don't understand why it's overfueling at idle though. Changing jets won't correct that at all, so I don't think that's an issue. I've already adjusted idle mix screws for maximum vacuum, so those are close.
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bluedge8
Active member
Still have the Holley on?
Check float level at idle
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Check float level at idle
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6speedsd
New member
Float level is middle of the sight glass, which is what this carb calls for (has the sight glass, not plugs). Regulator is set to 7psi at idle.
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gwunter
Active member
If you get one of those fuel/air ratio gauges that were mentioned about it really might help you tune this. Really sounds like too much fuel getting into the carb and then pushed past the primary.
psduser1
Well-known member
Adjust the vacuum to a slightly higher number? Less vacuum. That is what allows the fuel to flow through the idle circuit. The tradeoff may be a slight stumble off idle, but with patience, you should be able to minimize that. I don't know offhand all the details on those carbs, but if there is no internal idle adjustments, you could have a small compromise.
Check the butterfly shaft as well, a reman could leak air there, and make it almost impossible to get and keep the idle where you want it.
6speedsd
New member
I really do need to just buy that damn thing. I don't know why I keep putting it off. I'm wondering if dropping the float level a little would help? Might starve at higher rpms though. I know this....about 3000rpms this thing seems right. It wakes up and becomes a totally different animal.
Carb is supposed to be all new, not a reman. I have vacuum set at it highest reading at idle with the idle mixture screws. Well, highest that remains steady.
I really havent had time to tinker with it lately. I drove it to work 3 days this week, but have been working a ton of hours so haven't messed with it In a bit.
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Carb is supposed to be all new, not a reman. I have vacuum set at it highest reading at idle with the idle mixture screws. Well, highest that remains steady.
I really havent had time to tinker with it lately. I drove it to work 3 days this week, but have been working a ton of hours so haven't messed with it In a bit.
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lincolnlocker
Well-known member
how many rpm does it idle at?
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6speedsd
New member
In park I have it set around 750. In gear it's something like 600-650
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A few more thoughts..I'd consider going to 5 psi on regulator. Plug the brake booster line and recheck vacuum- those can be a big vac leak.. Make sure throttle blades aren't open too far to open transfer ports. Spray wd40 around throttle shafts to insure no vac leaks.
How much vacuum are you getting at idle?
How much vacuum are you getting at idle?
6speedsd
New member
Truck is still manual brakes, so there is no booster. The carb has a plugged port for the booster on the back, but it was screwed in tight (was an actual pipe plug, comes with threaded nipple to run booster line) when I installed it.
I'll drop the pressure and see how it acts. I was worried about a pressure drop and starving it with it that low, but than again I haven't messed with gas stuff it years, so just making assumptions.
I don't remember how much vacuum I got. I'll have to check it again to answer that.
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6speedsd
New member
Hows this
https://youtu.be/ItZQVOuoEkk
Idle in park is about 800rpm, and 16ish vacuum. Drop it to drive, and it drops to 12ish... In drive its about 600rpms. Power valve is a 6.5.... should I be considering a smaller one? And shouldn't I see more vacuum at idle than that? I thought 17-22 was the golden range, or is my cam the reason for the lower numbers?
I dropped regulator to 5psi. Still smells rich at idle. Drive for about 15 miles and I notice now having a slight stumble off idle. I opened the idle screws up a half turn and got about one more inch of vacuum. Haven't driven it since doing that though. Last time I adjusted those I had idle rpm about 650ish, so that may be why I gained a little vacuum by opening them.
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https://youtu.be/ItZQVOuoEkk
Idle in park is about 800rpm, and 16ish vacuum. Drop it to drive, and it drops to 12ish... In drive its about 600rpms. Power valve is a 6.5.... should I be considering a smaller one? And shouldn't I see more vacuum at idle than that? I thought 17-22 was the golden range, or is my cam the reason for the lower numbers?
I dropped regulator to 5psi. Still smells rich at idle. Drive for about 15 miles and I notice now having a slight stumble off idle. I opened the idle screws up a half turn and got about one more inch of vacuum. Haven't driven it since doing that though. Last time I adjusted those I had idle rpm about 650ish, so that may be why I gained a little vacuum by opening them.
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I'd think you'd have a little more vacuum with that cam. The idle drop seems fine for a stockish converter. You've got idle screws about 1.5-2 turns out? Timing at about 12-13? No change with plugged advance line? Sorry if I'm plowing old ground and you've already reported this - I haven't been watching the thread closely.
The only other thing I could think of is a valley intake/ head sealing issue but it's not sucking oil.
The only other thing I could think of is a valley intake/ head sealing issue but it's not sucking oil.
psduser1
Well-known member
One step at a time, lol. If you make more than one adjustment, you'll just make more work for yourself.
The vacuum number means sh!t, it's just a place to start. The higher your idle rpms, the less effect your idle screws will have.
As suggested, make sure there aren't any vacuum leaks.
The vacuum number means sh!t, it's just a place to start. The higher your idle rpms, the less effect your idle screws will have.
As suggested, make sure there aren't any vacuum leaks.
6speedsd
New member
Timing at idle is about 10, idle screws I think are at 2 turns now.
I don't think I have any vacuum leaks, but I think I'm going to buy new tubing and just replace all of it just to be sure. Can't hurt right?
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I don't think I have any vacuum leaks, but I think I'm going to buy new tubing and just replace all of it just to be sure. Can't hurt right?
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ja_cain
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I like using a small bottle of propane with a barbed fitting adapter so you can put a hose on it. Much easier (and no mess) to pinpoint vacuum leaks.
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