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Discussion Starter #1
the old Motorcraft carb on the 67 has given me some trouble so i swapped it for a Holley that a buddy had sitting in his garage. i bolted the Holley up and the car ran great. i let the car sit for a few hours and i tried to crank it up. it took a LONG time for it to crank ( so long i wore the weak battery ran down and i needed a jump ) and when it did start, it idled really really bad and there was alot of black smoke coming out the exhaust. for some reason when i pressed the throttle, it would raise and stick about 1000rpm above idle and stay there for a few seconds before it settled back down to its regular idle. ( still really bad idle though ). i let it sit overnight and after work i messed with it more. the float on the front bowl ws high so i lowered it and the jets in it wer eway to big so i swapped them from teh 72's to some 65's that i had in the garage. fired it up, played with the idle screws a bit and it ran like a champ. it had a bit of a bog that reminded me of too light a spring in the vacuum secondaries. if i gassed it a bit and it still blew some smoke. after sittig for a few hours i went back out and it was hard to start again. it eventually fired and it ran rough again and if i gassed it, ALOT of smoke would come out the tailpipe. infact, so much smoke that my bro- in law who was smoking and the time started to choke lol. any ideas whats wrong with the carb? its a 600 Holley, vacuum secondaries with a manual choke thats disconnected. its on a289 as well. im probably gonna put the Motorcrap carb back on but that doesnt run so well either ( bogs off idle pretty bad ). someone told me that maybe the power valve? im lost lol. thoughts? suggestions? ridicule?
 

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Most common cause of this sort of thing with Holleys is a blown power valve. A couple of times I have seen bad metering blocks have a porous area but that's pretty rare. If you've changed jets then a PV should be no problem.

FWIW, experience with an 84 302 H.O. found that 68's ran best on the jets. I'm betting you'll find the 65's just a tiny bit lean at heavier applications of the throttle just before secondary opening. If the PV is indeed blown, or at least leaking, it would cover any leanness in the jetting at this point.
 

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Discussion Starter #3
cool. how do i change teh power valve now? lol. im still a rookie with carbs.
 

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I go with Parker, its the power valve. Remove the front bowl and its screwed into the metering block. (About 1" in diameter with a hole in the center with a rubber diapraghm in it). Screw the old one out and a new one in. Try to use the correct one though, I can't remember the exact specs for it but if I remember correct it should be 2" of vacuum below your idle reading (I think thats right but I cant remember and I dont have the specs here at home). The old 289 probably is lucky to have 15" now so I'd use that as a starting point. Someone else here may remember the spec for the power valve for you though and if not goto Holley's web site. They have tech area's with ANY THING you could EVER possibly want to nkow about a carb there. Even the list # to CFM size charts!
Scott
 

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Most 600 vac sec Holleys have a PV rated to open at 6.5inHg. You should be able to get one at your local parts store that stocks Holleys parts. It'll have the rating on the label.

I was going to mention last night that it is my opinion that a properly operating Motorcraft carb will beat a Holley in all respects on a stock or near stock engine. Once you start doing mods to an engine the Holley is the better choice for ease of tunability and parts to do it with.
 

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Discussion Starter #6 (Edited)
ok ok... i replaced the power valve and even rejetted teh carb. it didnt work. when you start the car it seems to run fine for about a minute or two, then it starts to stumble slightly and then a few seconds later it gets real bad and then will die. then its a pain to start up again, hence why ive killed the battery a few times. im at a loss of ideas right now as to what i might have done wrong in this carb swap so i need to ask for more help. the yellow arrow shows a port that i saw smoke coming out of for some reason. im not really sure what it is for. the choke was disconnected and i dont know if maybe thats what was causing it. the blue circle is the only other exposed port on the carb, and i thought that all Holleys had that one exposed. so i didnt think anything of it. the hose leading up to that is attached to a metal tube that goes to the exhaust manifold. when my car went to a 4bbl, those tubes were simply left in place unplugged and it made no difference. so once again, i didnt think anything of it. the 67 has smog equipment, so maybe that has something to do with it?? it also seemed to be having alot of smoke come out the PCV valve as well ( blow-by?). im getting mad at this car already and i mgiht just put the old Motorcraft carb back on and deal with how that runs. if i put that one back on and it still runs bad, well.... looks like the 67 will be exiting this world that much faster.
 

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Discussion Starter #7
this is a shot of the hose that is attached to the smog equipment. ( EGR valve maybe? ) when i was revving the engine and keeping the idle up ( to prevent it from dying ) i felt air coming out of this hose. now, its just normally attached to the air cleaner right? which is why i didnt think anything of it to be unplugged. the 69 used to do something similar to this, but it would run great for a few minutes and misfire afer it warmed up. that turned out to be the points in the distributor. i havent checked these ones but it was just fine before the swap. im lost. and angry ....... :angryfi:
 

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the yellow arrow- thats for the choke assembly that should be there. Plug it with silicone or something.

not sure on the blue one, cant see it that well.

Rick
 

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the second picture is a backfire supression valve used with a thermactor system (says my manual).
 

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That's one ratty looking carb. How many people have jacked around with it over the years? I suggest getting one that is known to have all it's parts. In fact, why not just buy a new one?

You can screw around with one for a long time and not get anywhere. People drill passages, lose parts, install the wrong metering block for the application, install the wrong metering block gasket and all sorts of dumb stuff. It can be really hard to figure out what is wrong unless you have lots of experience with old Holleys. Sometimes it is better to just toss it in the trash and get a new one.
 

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Discussion Starter #12
the carb is supposed to have been rebuilt recently. a buddy of mine gave it ot me so i figured that it would be worth a shot. i didnt want to go out an dget a new carb and dump alot of cash into the 67 while i had it. oh well, i may wind up doing that or getting the Motorcraft rebuilt. well see.
 

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Sounds like it has the OTHER Holley problem then. I misunderstood exactly how the problem was occuring previously. The symptoms described sound like a flood-over and on a Holley it's usually the Secondary needle-and-seat assembly causing this because of debris in the N&S.

A quick way of checking is to get it to do it and then pull the secondary bowl sight plug. If a lot of fuel pours out you know you're on the right track.

If the secondary bowl is flooding then pull the N&S out by removing the lock screw and using the adjusting nut to back the N&S out. Do a visual inspection and I'll bet you'll find just a tiny little bit of debris on the needle. Blow that out and re-install using petroleum jelly, or at least silicone, to lube the O-ring. Run the N&S down until 2 1/2 to 3 threads show which will get you in the ball park for adjustment.

Oh BTW, I suppose the thing COULD have a sunk float. Easy way to check while the N&S is out is to use a thin screwdriver down where the N&S came out and push down lightly. If it feels like there's something pushing back then you're ok in that regard. If it just feels solid the the float could be sunk/stuck, but this is rare.
 

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Discussion Starter #14
PARKER -- you were close... it turns out i checked the secondary float bowl and saw that the level looked ok. for the hell of it i rechecked the front float bowl and alot of fuel spilled all over. dont know why, because i had adjusted it before and it was fine. i loweed the float again and now i have had the car currently running damn near perfect for about 15 minutes. im gonna let it heat up then try and start it again later. maybe the float is sunk in the front. well see.
 

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^^^

Interesting. The fronts almost never do that. The rear seems to be affected primarily because the flow back there is very low most of the time and there's no chance for a small bit of debris to flow through. In fact I've managed to clear debris in the secondary N&S when I know its happening by getting clear of traffic and making a top-end run at WOT. This happens more after carb work as some debris from the hose can be introduced.

Anyway with that view of flood-overs, it follows that with the higher fuel flow through the primary N&S they would be more immune to this sort of thing. But I suppose a large enough bit could find its way there especially after a recent install.
 
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