zac_F71
Well-Known Member
Could a cut off choke horn enhance the signal to the power valve and cause it to open earlier than it's rated to?
carb question (Holley)
- Thread starter zac_F71
- Start date
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Not sure about that. Usually the power valve is operated by manifold vacuum, so it may be possible. I really don't see why it would though. Your manifold vacuum should be the same.
zac_F71
Well-Known Member
I see WELL the problem I'm having is there is fuel dripping out of the primary boosters - so much so it won't let it idle (floods it and stalls)
Sounds like a float adjustment issue to me. Or a bad needle and seat, or maybe it just needs a good cleaning.
Have you checked your manifold vacuum and made sure you have the correct PV?
Have you checked your manifold vacuum and made sure you have the correct PV?
zac_F71
Well-Known Member
floats have been adjusted and re-adjusted - I have new needle and seats I'll honestly probably re-rebuild it here and start from scratch
manifold vacuum is around 9" at 2,000rpm (lowest it will run) it has a 6.5 PV now and I have a 5.5 to try
I used a QF renew kit and now have a Holley brand kit to redo everything again
manifold vacuum is around 9" at 2,000rpm (lowest it will run) it has a 6.5 PV now and I have a 5.5 to try
I used a QF renew kit and now have a Holley brand kit to redo everything again
If you are only running 9" you need a 4.5 PV. Are you sure you don't have a vacuum leak somewhere?
zac_F71
Well-Known Member
no outside vacuum leaks (checked by spraying brake cleaner) could have internal leaks but there is no way to test
go to know on the PV! TY!
EDIT- the vacuum reading could be higher I haven't started the car in about 2 weeks so I can't remember off hand what it was
I wouldn't mess with a PV rating at all until you get the idle issue under control.
2000 RPM is WAY TOO HIGH for anything short of a Pro Stock/Fuel engine.
At that rpm it's going have a real good chance to pull fuel from the boosters.
I don't know what the tune up is, but, start at about 14-16 BTDC for initial timing.
If you have power brakes, plug that line at the manifold too...
2000 RPM is WAY TOO HIGH for anything short of a Pro Stock/Fuel engine.
At that rpm it's going have a real good chance to pull fuel from the boosters.
I don't know what the tune up is, but, start at about 14-16 BTDC for initial timing.
If you have power brakes, plug that line at the manifold too...
No kidding. That's why i thought vacuum leak maybe. He says it won't run very well below that.
A little more info on the engine might help.
breakstuff
Well-Known Member
What is your fuel pressure? Too much will blow fuel past the needle and seat regardless of where you set your floats. 6 PSI is all a holley needs.
zac_F71
Well-Known Member
I'm probably gonna get in trouble but this is on my 83 Mustang 302 AFR aluminum heads F303 cam (226/226 @.050 .550/.550 w/ 1.72 RR) 10.1:1 static CR
the carb is a Holley 4777 4150 - fuel pressure is regulated at 6psi (so the gauge says)
the dripping from the boosters is excessive for sure (It makes a missing sound but it's not missing) is the best way to describe it
It wants to idle and once it did idle at 900rpm for about 15 seconds but the dripping flooded it
the carb is a Holley 4777 4150 - fuel pressure is regulated at 6psi (so the gauge says)
the dripping from the boosters is excessive for sure (It makes a missing sound but it's not missing) is the best way to describe it
It wants to idle and once it did idle at 900rpm for about 15 seconds but the dripping flooded it
Lonewolf3165
Living the Dream!
The power valve is probably blown out due to a backfire throught the carb at one time. It doesn't take much, a hesistation when coming off idle when cold & poof! More probable too since you have no choke to help it warm up either. Cutting the choke horn off (assuming it was done correctly & not butchered up) shouldn't cause the power valve to open early. You also want to make sure the idle circuit isn't blocked otherwise that will cause the fuel to pull over.
I'd put a new power valve in it & clean out the idle circuits real good & go from there.
Funny, I had damn near the same set up on my '83 Mustang GT too. Probably put a 1/2 dozen power valves in that car.
I'd put a new power valve in it & clean out the idle circuits real good & go from there.
Funny, I had damn near the same set up on my '83 Mustang GT too. Probably put a 1/2 dozen power valves in that car.
That should idle EASILY at about 800-900 rpm without issue. What's the initial timing on the engine?
You need to figure out why the boosters are dripping. Float level, bad float. Try turning the float adjuster down 1 full turn and see if that helps. Give it a couple of revs to so float level drops and check for dripping. The dripping boosters are the likely reason the car won't idle.
You need to figure out why the boosters are dripping. Float level, bad float. Try turning the float adjuster down 1 full turn and see if that helps. Give it a couple of revs to so float level drops and check for dripping. The dripping boosters are the likely reason the car won't idle.
zac_F71
Well-Known Member
I see the power valve is probably blown then it has backfired twice on me
mullinax95
Well-Known Member
I would try/borrow another (known to be good) carb on it and see what happens.
dovercrossing
Go Mountaineers
Edelbrock/ carter nuff said!
zac_F71
Well-Known Member
I can't I don't know anyone in my area.. at all just family and they don't have one..
If that carb is less than about 20 years old, it should have the PV protection circuit in it.
I have cars that pull 7" of vacuum and have 10.5 power valves in them... If the idle is correct the PV isn't even in the circuit at all.
I have cars that pull 7" of vacuum and have 10.5 power valves in them... If the idle is correct the PV isn't even in the circuit at all.
Lonewolf3165
Living the Dream!
Put a power valve in it & see how it is. It doesn't cost that much & doesn't take that long to do.
zac_F71
Well-Known Member
it has "05" in the date stamp in the main body by where the choke rod comes through the hat
if that makes sense but as far as year I have no clue - it does have a PV but no clue on the protection
Lonewolf3165
Living the Dream!
True but if it blows out then it is open all the time & would affect it at idle. Mine used to surge like an alcohol funny car at idle when it would blow.
Set the timing FIRST before you waste any more time! Do you know what the initial timing is set at right now? It's going to go down as you reduce RPM is my bet. I'd get it started and crank a bunch of advance into it and start turning the idle down.
Even if the PV is blown, at idle it SHOULD NOT have enough air flow through the venturis to pull fuel from the boosters... PERIOD! That circuit should not be active at all at idle. That indicitive of the throttle plates being too far open at idle.
Even if the PV is blown, at idle it SHOULD NOT have enough air flow through the venturis to pull fuel from the boosters... PERIOD! That circuit should not be active at all at idle. That indicitive of the throttle plates being too far open at idle.
Lonewolf3165
Living the Dream!
Timing wont make the fuel pull over into the booster... PERIOD!
The power vavle is operated by a little diaphram in it. IF it's working normally you are correct. BUT if it gets blown out it will cause it to dump too much fuel into it because it can't close itself. Regardless of the throttle plates position.
I normally agree with you on the affect of ignition timing at idle, but what I think he's got here is an over rich condition. It's very likely, and confirmed by the op that it has backfired & probably blew out the PV. Espescially with no choke on it. I know Holley put a protection in later carbs but I have seen even those get blown out too. Hell, it may not have gotten blown out & may have just gone bad for whatever reason.
It's too hard to sit here at our computers & not have our own eyes on the car to see 1st hand what's going on where. We're all just trying to give friendly advice to a troubled mopar brother.
OldmanRick
Well-Known Member
I understand where your coming from crackedback. He's gotta get the idle down some how because if there's no vacuum leak then for it to idle that high the throttle blades definetely have the transfer slot uncovered.
I reread and thought he had tried a new PV, i guess not yet, so your right wolf that may be his issue.
I reread and thought he had tried a new PV, i guess not yet, so your right wolf that may be his issue.
Lonewolf3165
Living the Dream!
I think he has it turned up that high because it won't stay running any lower than that. More info is definetly needed.
When did the problem occur? Was the carb put on it & the problem immediate, or did this start to happen on its own? Any changes made to the engine to coincide with the problem?
When did the problem occur? Was the carb put on it & the problem immediate, or did this start to happen on its own? Any changes made to the engine to coincide with the problem?
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