Possible ignition issue
Thread Starter
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Senior User
Joined: Oct 2015
Posts: 445
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From: Bismarck, ND
Appreciate the help guys! Took the liberty and adjusted the idle mixture screws a bit (probably not set at the best but oh well) and rotated distributor about 1/2 inch counter clockwise (advanced?) And most the stumbling went away! I also saw a performance improvement too 
but it still stumbles a bit at higher rpms and under load but it's a huge improvement. So hopefully this will fix my issue but I don't understand why it would just start running bad?
but it still stumbles a bit at higher rpms and under load but it's a huge improvement. So hopefully this will fix my issue but I don't understand why it would just start running bad?
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Don't guess. Measure twice, cut once. Everything sort of affects something else when it comes to tuning. Clockwise on a Ford distributor advances ignition timing. It doesn't take much to make a huge change. The width of a pencil line equals about 2 degrees. Timing can be WAY off and still sort of idle OK. For best performance and economy and pollution you want to dial everything in careful.
Thread Starter
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Senior User
Joined: Oct 2015
Posts: 445
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From: Bismarck, ND
Don't guess. Measure twice, cut once. Everything sort of affects something else when it comes to tuning. Clockwise on a Ford distributor advances ignition timing. It doesn't take much to make a huge change. The width of a pencil line equals about 2 degrees. Timing can be WAY off and still sort of idle OK. For best performance and economy and pollution you want to dial everything in careful.
Senior User
Joined: Dec 2014
Posts: 288
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From: Pocahontas, Iowa.
Older Holly 4bbl Carbs had power valves that blew out upon a backfire. After that the engine would never run right.
If it's a Holly 4 barrel, start the truck and let it warm up. Turn the idle mixture screws clockwise till they bottom out. If you turn them both in completely and the engine still runs...power valve.
Holly's new valves have a by-pass so they rarely blow upon backfire.
Bill
If it's a Holly 4 barrel, start the truck and let it warm up. Turn the idle mixture screws clockwise till they bottom out. If you turn them both in completely and the engine still runs...power valve.
Holly's new valves have a by-pass so they rarely blow upon backfire.
Bill
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Senior User
Joined: Oct 2015
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From: Bismarck, ND
So I finally got a timing light with adjustable advance dial and my timing showed about 35° BTDC before I retarded the timing down to 6° BTDC. All I have to say is HOW and WHY? I sincerely hoping my timing chain jumped and the PO didn't feel the need to advance it that far... unfortunately with my brake issue I can't test drive the truck and see how it runs but I hope it's better!
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Senior User
Joined: Oct 2015
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From: Bismarck, ND
Yes to all, I didn't start at 0 advance as the marker wasn't even lining up with any if the numbers. So I moved the dial till it lined up.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
With a base timing set at 6* bftc then what was the timing after connecting the vacuum advance, if you get a rattle & ping while starting out from a stop, or while driving you man need to adjust the vacuum advance through the advance hose nipple with an Allen wrench to cut back of the advance some by turning the Allen screw inward to the right that is.
Orich
Orich
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Senior User
Joined: Oct 2015
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From: Bismarck, ND
Well attaching vacuum advance picked it up about 2 degrees, but Im running into issues where the most drive able BTDC setting the idle fluctuates still, so when it went down to 600 I kept that reading. But the engine STILL stumbles and if the throttle is held at 1500+ rpms the engine will bog down unless I give it more gas.
Also it runs better with the choke on. So I'm narrowing the issue down to either the carb is running lean (don't know why it would just all the sudden start to at once) or proper fuel isn't getting to the carb. I'm gonna check fuel pump/filter when engine cools
Also it runs better with the choke on. So I'm narrowing the issue down to either the carb is running lean (don't know why it would just all the sudden start to at once) or proper fuel isn't getting to the carb. I'm gonna check fuel pump/filter when engine cools
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Senior User
Joined: Oct 2015
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From: Bismarck, ND
I'll have to answer that tomorrow as I'm bring my mother and sister into town for the rodeo. And I'm pooped from sitting outside for 7 hours drinking on my truck.
What else could be my cause? Bad carb or fuel pump?
What else could be my cause? Bad carb or fuel pump?
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Hmm with out going to the back pages and rereading them.
If carb has a bad power valve does funny things.
If both A/F jets are closed and engine keep running then carb P/V is bad.
Orich
If carb has a bad power valve does funny things.
If both A/F jets are closed and engine keep running then carb P/V is bad.
Orich
Thread Starter
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Senior User
Joined: Oct 2015
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From: Bismarck, ND
It's weird because under half throttle there is basically no power (and I mean almost non existant) unless you have the choke on, but slam the gas it stumbles a bit and just takes off like a rocket
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
The Float level maybe set way low to.
Orich
Tuned
Joined: Oct 2014
Posts: 406
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From: Tucson Arizona
It *might* be plugged air-bleeds in the Holley.
Right inside of the air-horn in front of the throttlebores are 4 small jets.
Small enough that it doesn't take too terribly much to clog one. Or more.
I use a can of spray carb-cleaner with the tube attached to the sprayhead. Spray the whole area well. Then hold the end of the tube directly on the jets and give each one a thorough cleaning.
Caution the spray is very likely to squirt right back into your face.
What kind of aircleaner do you run?
I've had the clogged jets problem, usually, when running a K&N.
Right inside of the air-horn in front of the throttlebores are 4 small jets.
Small enough that it doesn't take too terribly much to clog one. Or more.
I use a can of spray carb-cleaner with the tube attached to the sprayhead. Spray the whole area well. Then hold the end of the tube directly on the jets and give each one a thorough cleaning.
Caution the spray is very likely to squirt right back into your face.
What kind of aircleaner do you run?
I've had the clogged jets problem, usually, when running a K&N.