Holley 4160 problems! Bought vehicle, 350 small block, Holley 4160. Replaced primary pump and other parts in the primary fuel bowl to get vehicle running. Ran ok than developed a whistling vacuum leak. Pulled carb replaced gaskets and rebuilt back fuel bowl. Put it all back together, ran ok for ten miles, now it will not idle when putting it into gear, drive or reverse. Adjust float level up and down, no good. Adjusted air mix needles, no good. Adjusted idle screw, no help. Adjusted timing no help. Shot cab cleaner through the needle screw ports and compressed air, no help. fuel filters clean exhaust smells rich, some black smoke when reved up Adjusted pump level screw, no help When taking fuel bowl sight plug out to check float level in the primary bowl the idle would normalize...sucking air in...? Next recourse pull primary fuel bowl , check it out, replace the power valve assembly, possible bad fuel pump? Has new plugs, wires, HEI Rig is a 57 Willys wagon Thanks for any ideas. Carl
Did you use thread sealer when you put the carb back on? Hey, I've done it, messed up a couple carbs learning not to use it again. It will cause Johnny's scenario above.
Shoot carb cleaner thru the air bleeds and vent tube. Be sure the air cleaner lid isn’t sucking down too love to the vent tube. SPark
Sometimes running rich will be caused by a pooched power valve. Another possible issue, is that sometimes the faces of the blocks can be warped, and when you assemble the carb with new gaskets, the carb will not be properly sealed. Bob
Hoping it is the power valve...has ran a little rich from day one. Maybe when I fixed the vacuum leaks on the carb, the poor power valve overwhelmed everything ...
Did it backfire at any time? That will do the power valve in! Newer carbs have a “ power valve saver valve” in them to help prevent this. Big problem on older carbs. Bones
Spot fixing carburetors is like a NASCAR driver saying he has a left side flat and they only replace the left side tires on a pit stop and then he has to come back in to replace the right side tires that were flat in the first place. On a Holley the first place to look for a problem is the power valve; is it the right one for the tune, is it blown, is it the right one for the carburetor.
Don't forget while you have the carb apart. Put a straight edge diagonally across the carb faces and the plates to check for distortion. If previous owners have over torqued the screws that are used to attach the metering plates and the bowls, the carb faces will probably be warped and require gentle filing to true them up again. Bob
Your power valve is probably junk, especially if it’s an older carb. I think they started putting the saver valves in about twenty years ago. If yours does not have one, they make a kit to put one in for about $12. Did quite a few back in the day. For me is was just part off a rebuild. Bones
If it is the power valve it must be loose then. Blown power valves diaphragm alone will not make a carb go rich, the opposite. Now if it's loose it will allow vacuum to pull fuel from bowl and create vacuum within in the bowl (per OP's words) providing vent tube is plugged.
Huh ??? The only thing between manifold vacuum and the float bowl is the diaphragm , with a blown diaphragm , fuel is sucked directly into the manifold ......
PV protection since 1992, an easy check for a blown valve is lean out the idle mixture screws, if the engine stumbles/ stalls, the power valve is not blown. It does happen but it's one of those stories that gets told and retold over the internet and takes on a life of its own. Somebody at Fordbarn tested some with a Mityvac and found they can be sometimes be way off their listed opening point. Probably worth checking before installing.
Power valves in the older carbs blew quite often. Holley invented Power valve saver valves and included them in the later carbs to cure this problem. If it wasn’t a problem, they wouldn’t have taken the time and money to do this. If your power valve ruptures the diaphragm, you will go very rich as the fuel will flow through the diaphragm directly into the intake manifold. It depended on the driver as to how often it blew, backfires were/are the main cause of failed power valves. Bones
Backfire? Or backfire through the carb? Both?? It was more of a perfomance application problem? I've never had a bad power valve just zookin' around. I'm glad I never paid attention to any of this stuff years ago, I wouldn't left the garage. Points, generators, drum brakes, and now carbs.
Truck64, it was a trip, back then. I usually drive my modern cars around, but I get reminded of the old days, every time I take one of my 65 Fords out for a cruise. Start it up, jiggle the throttle a little till it warms up a little, put it in gear, wiggle the foot feed, to richen the mixture a little, very lightly, to avoid coffing/ backfire through the carb. Down the road a spell you are ready to go. You kinda had to “ learn” a car. The power valve problem was equally spread between OEM and performance carbs.... as they were very similar. The diaphragm power valve was what made Holley famous..... and also cussed! It was a different world back then. Better power valves and power valve saver valves have brought the Holley back. Bones
Great info. Looks like it was the power valve! Idles nice and runs smooth. It is still a bit rich though. Float level seems good, air mix needles are just one and an eighth to one and a quarter turn out. Will check a few plugs tomorrow. The power valve is 7.5, that is what came with the kit. Could not make out what the old one was. To much fun ;-)
The vac port in the carb base is always exposed to manifold vacuum .that's what holds the PV closed , when the vacuum falls below the PV spring tension , it opens the PV. If the PV diaphragm is ruptured , fuel will be drawn through the PV because vac won't hold a ruptured diaphragm closed ...
Johnny Gee, take a Holley carb, leave the power valve out( blown power valve ),and try to fill the front fuel bowel. You can’t do it! Bones
This guy claims (I think) a ruptured power valve can't affect idle mixture. Even if true, it would definitely bugger the fuel mix at cruise. For the same reason it is very important to select the proper PV that does not provide any enrichment at cruise, especially when deciding on jetting calibration.
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