Resurgence of a F100

needen$77 · Jun 25, 2017

I love that shade of orange and i live in tn but dont care. Dukes of hazard yyyyeeeessss

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6speedsd · Jun 26, 2017

Where in TN?

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needen$77 · Jun 26, 2017

Clarksville

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6speedsd · Jun 29, 2017

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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bluedge8 · Jun 30, 2017

Still have the Holley on?
Check float level at idle

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Magnum PD · Jun 30, 2017

Fuel regulator? Pushing gas through?

6speedsd · Jun 30, 2017

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 · Jun 30, 2017

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 · Jun 30, 2017

6speedsd said:
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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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 · Jun 30, 2017

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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lincolnlocker · Jul 1, 2017

how many rpm does it idle at?

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6speedsd · Jul 2, 2017

In park I have it set around 750. In gear it's something like 600-650

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mandkole · Jul 2, 2017

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?

6speedsd · Jul 2, 2017

mandkole said:
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?

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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mandkole · Jul 2, 2017

These carbs don't need a ton of pressure, and definitely don't like too much --5 is fine . Unless you can physically see fuel dribbling down the venturi at idle, id eliminate the needle valve.

6speedsd · Jul 2, 2017

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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mandkole · Jul 2, 2017

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.

psduser1 · Jul 2, 2017

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.

6speedsd · Jul 2, 2017

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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ja_cain · Jul 3, 2017

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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