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Bad powervalve on Holley 650

mountainexplorer

mountainexplorer

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There's a Holley 650 Double pumper on a 454 in a '73 Blazer I recently bought. The timing was set way too far advanced, so we got everything dialed in, but now, when I put it in gear, it immediately tries to die (or does die). And if I really get on the gas when it's still a bit cold, you can hear it backfiring out the left side of the exhaust. Sounds like a miss at idle, too.

Any of these signs of a power valve going out?

I never have good luck with Holleys. /forums/images/graemlins/confused.gif
 
If the power valve goes bad it will flood the engine cuz the valve isn't opening under a load only it's always open dumping fuel in to the engine.
 
sounds like your timing is off, or the firing order is incorrect, check your firing order and which wire goes to which plug. My buddy had the same backfire problem I asked him if he had all the wires on correctly, was told yes when I got there I found one wire on the wrong cylinder. Like the other post said your power valve controls when your secondaries open. If it is bad or popped you will see fuel dripping in your secondaries. Vacuum drops power valve opens letting gas go to the secondaries. If you keep letting it backfire it will pop the power valve and then it will be bad a if it is not already. The newer holley carbs have a check valve to protect the power valve from backfires /forums/images/graemlins/truck.gif
 
It's an older carb. It runs fine when it's warmed up though. Doesnt like to idle very low. Has a bit of a miss, but doesnt backfire at all when its warm. Timing was set at 20 degrees advanced, but we brought it back to 8 degress. Carb doesnt seem to flood out at all.

But it's a hard starter in the mornings, and stalls easily when I hit any big bumps (I was out at the ORV park yesterday). Otherwise, did ok on hills...only stalled out a couple times.

I'm probably gonna put an Edelbrock or Carter on it that I have in the garage, just to see how it changes.
 
not to bust your stones, but, the power valve doesn't control the secondaries. In the metering block for the front, and sometimes rear barrels, ther are vaccum operated valves that add fuel under "power" similar in function to the accelorater piston on a Q-jet. to add fuel when accelorating. The secondaries on his carb are mechanical linkage. the other option is a vaccum secondaries, which have a vaccum can attached to the secondary linkage. /forums/images/graemlins/k5.gif /forums/images/graemlins/pimp1.gif
 
I love Holley carbs. for racing! not 4 wheeling. The double pumpers have center hung floats which make them flood out or stall when wheeling. the floats don't take angles to well. Holley makes a fuel bowl conversion to fix this problem. part # 34-3. The problem with Holley carbs is that they are "VERY" tuneable. which in turn makes them sensitive to many outside elements. Because of venturi design, when cold these carbs can "freeze" up in the venturi's causing the fuel to puddle. It may also be neccessary to put richer jets in to compensate for the colder air temp. You must understand, the double pumpers are designed for performance and not overall driveability. can you tell when it "backfires" if it's because it's rich ( any black smoke or carb flames) or the more common winter problem of running lean( dry farts!) What is the air temp outside when it runs worst? what type of air filter are you running? do you drive this everyday? /forums/images/graemlins/ears.gif
 
Check your float level. Holleys LOVE to stick floats, either up OR down. I run spring loaded needle and seats on mine.
 
It's been down into the 20's at nights, and up to the mid 30's during the day here. It's just an open air filter (cheap paper one). I've driven it a little bit every day since I got it a week ago, but the guy I got it from hadnt driven it much in the last year or so. I remember he did say something about putting richer jets in during the winter.
 
Now I'm mad. I put an Edelbrock on it that I know ran PERFECT on another 454 I had. All wires are in proper order, all vacuum lines hooked up properly...and it took me like 2 minutes to start the thing! /forums/images/graemlins/angryfire.gif It kept backfiring through the carb with huge flames (never did with the Holley), and eventually, I got it to run and warm up. The backfiring eventually quit. I drove it, but it seemed like it had a dead spot. A bit worse than before, even though I know this is a perfect carb. So I checked spark plugs. They definitely looked old. So I changed spark plugs. Now, the thing dies as soon as I give it any gas. I tried driving it and all it does is sputter, backfire, and miss. /forums/images/graemlins/angryfire.gif I hate it when I replace bad parts with good parts and things run worse! /forums/images/graemlins/angryfire.gif
 
welcome to the world of "one size fits all" carbs. Even with the edelbrock, tuning is needed. These carbs are set up for a basic engine's needs. Performance options will change what the engine needs. I say put the holley back on, richen the jets a little, and use an late model o.e.m. style air filter assembly and hook up the warm air intake to draw in warm air from exaust manifold. That will help alot! Then save up ypur money for a fuel injection system!
 
Think it could be a problem other than the carb? I'm half tempted to put the Holley back on and throw those garbage plugs back in, just to see if it runs better than it does now.
 
if the problem only happens when it's cold, I would say the problem is most likely carb/air intake related. Performance carbs are not set up to run in colder weather. I wouls put the holley on(only cause i know how to tune them) and go with a factory style air filter and hook up the warm air intake. that could solve alot of the problem. Do you know what size cam is in this?
 
You got an ignition problem homie. I'd bet your advance wieghts are all crudded up, or something along those lines. Take the distributor apart, and drop the coin for good quality replacement stuff. /forums/images/graemlins/frown.gif
 
Well, right now, its running bad warm or cold. Not that radical of a cam, just like a mild RV. Cant hear a lope at idle. It always did sound like it had a miss though. Last Sunday, I drove through quite a few puddles, one of which splashed some water up onto the motor. It sputtered and barely ran for a little while, but seemed to dry out and run better after a few minutes. That was with the Holley and old plugs.
 
you may have carb problems but you for sure have ignition troubles that you are blaming on the holley.
bablazer is on the right track.
I would start by asking you to give up the Holley list # so that we can determine what this "650 holley" really is.
most "650 holleys" that I have seen are actually an list#1850 holley 600 vacuum secondary.
usually it is a good thing as a 650 doublepumper is not the best choice for a streetcar.
the slightly more expensive 600 electric choke carb is the best holley for a SBC that does DD duty IMO

list # can be found on the choke horn facing the front of the vehicle
 
Had this similar problem before with a Holley and later found that I had accidentally put the wrong gasket between the mainbody and the jet plate on the front.
 
I had the same problem with my K-5,backfiring,no power,missing.My timing was way off.My springs were shot on the mech. advance inside the distributor and DO NOT trust the timing tab on the crank.I have mine running great and the timing marks don't even show up on my tab.I put a new weight and spring kit in from Mr. Gasket,bumped #1cylinder up to the top,set my distributor accordingly and test drove.Come to find out I also had to put bigger jets in my Holley,60's to 72's,and now I'm running great.I run my vacuum advance on manifold vacuum but try ported to see which is best.Hope this help's.GOD Bless,jtpepper
 
Just to be sure that the carb wasnt the problem, I put another Carter AFB on, and it ran the same. It even started to get progressively worse. So, tonight, I yanked out the distributor and dropped in an HEI. I just threw on some old used plug wires and set the timing by eyeballing it. Hooked everything up, went to start it, fired right up. Idled smooth, took it for a drive, and now it feels like a 454 should.

So, nothing should be wrong with the Holley. It was all in the distributor. Thanks everyone for the tips and help.
 
4777 is a 650 pumper.
been awhile but I think the -4 may be either factory rebuild or the newer versio with plastic accel pump arms etc
 
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