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Quickfuel (like Holley) power valve

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Quickfuel (like Holley) power valve

Old 08-23-2019, 07:29 PM
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Default Quickfuel (like Holley) power valve

You Holley guys would already have heard of this, but I think it's worth posting for the next new-to-Quickfuel guy.

I just had yet another boat issue. I sure am getting an education.

I admitted on here that I hadn't put in my exhaust flappers and got a bit of a talking to about that. So I put them in the other day.

Then I reset my idle mixture a little leaner because I had seen it way too rich when I had my AFR system running.
Well the engine stalled during my idle setting session and when I restarted it I got a backfire.
I knew about the possibility that a backfire could lunch my power valve. But I finished adjusting my 4 corner idle and put the cover on. Next time in the lake, misfire at 2800 rpm and up. Deteriorating idle, especially in gear.
It had rained buckets and my ignition got a wet down when I opened the hatch. So I checked the ignition. After all misfire-ignition? But Nope, it's OK.

Thankfully I had bought my carburetor from a reseller that offers lifetime service and is happy to do phone coaching. He was convinced the power valve was going to be bad, and he was right. I have read that there is a check ball to catch backfires, and he confirmed that it's there, but they still get damaged.
I had bought some before so I had two different sizes on hand. Put in the right one and voila. Perfect.

Another lesson, I missed a couple of weekdays on a lake that's kind of busy on weekends. I guess I saved some money on fuel though.

So the short version is, if you have a power valve carburetor and you get a backfire there's every possibility that you will need to change out the power valve. Keep some around, don't even chance it. Boating season is too brief as it is. Facepalm.

Last edited by NHGuy; 08-23-2019 at 07:34 PM.
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Old 08-23-2019, 08:46 PM
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That is one reason I am not a fan of Holley and it's clones.
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Old 08-23-2019, 09:59 PM
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I had holley carbs on boats since 2003. Everything from twin 850 quick fuels on blower motors, single dominator setups, and single 4150 setups. I can honestly say, ive never "blown" a powervalve.

i never leaned the engines out though. Also, i never make a habit of cranking the engines with the throttle blades cracked open. I see guys doing this all the time . A few pumps of the throttles, bring to idle , and crank. If it doesnt start that way, something is amiss with the carb setup, esp on the idle circuit.
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Old 08-24-2019, 12:07 AM
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Volvo penta and OMC used holley carbs for many years oem stock apps. Also Volvo used Demon carbs as well for OEM stock apps, Merc racing used holley as well. I have not seen a blown power valve in many many years from a backfire. But currently most everything is efi per what I see. Anyways a bit of read about it. . Years ago we got a SB about this as well.

https://www.enginebuildermag.com/201...y-carburetors/

Last edited by BUP; 08-24-2019 at 12:16 AM.
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Old 08-25-2019, 12:15 AM
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All I want to know is who did Holley pay off to get marine certified? Between the bowls that hang off the sides with 4 screws going through them or the metering blocks or the accelerator pumps in the bottom which all can (and have before) leak. IMHO for a boat that sits around for months at a time (gaskets dry out) not a fan of Holley.
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Old 08-25-2019, 08:07 AM
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I see alot of popped power valves on Holleys , old boats, accelerator pump is week , they gas it to pull there buddies on the tube , lean pop through the carb.
Bang its dead. Yes and the dried out gaskets.
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Old 08-25-2019, 01:25 PM
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I just got done doing some tuning on the edelbrock carb on this new to me 71 BBC monte carlo. I installed a wideband on it the other night. It felt lean to me , esp at cruise. Sure enough, it was pegging the afr meter at 16.0, and at wot was in the 15s. Im shocked the previous owner didnt melt it down. Probably thanks to the 26* total timing and stiff springs in the distributor he had.

After swapping jets, and metering rods, its much better. However at wot, its still in the mid 13s. Im running .113 and .110 jets in the thing, and its still lean. The single accelerator pump sucks. Changing jets is a pain in the azz. Have to remove the whole top plate, unhook choke arms, accelerator pump arm, try to thread jets in without cross threading them as they are vertical...idle circuitry is lame. I could have swapped jets in a 4150 in half the time it took to do the ones in the carter/edelbrock carb. And better not drop the power piston spring, metering rod spring, or the tiny hairpins that hold the linkage arms while doing so.

Probably a nice carb for a stock to mild engine, but for anything thats serious imo, they belong in the trash. Theres a reason you see holley double pumpers on just about everything thats built to run. The tuning possibilities are endless, the idle circuitry can be worked to feed anything from a 330hp 454, to fire breathing 572 that turns 7000+.
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Old 08-27-2019, 11:47 AM
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IMHO I don't think so Thunder. I hear what you are saying but to change jets in a Holley you are pulling the carb and taking it all the way down to the body to get to the metering block. A Edelbrock rods and step up springs are nothing to replace, a simple screw in the top to remove the cover plate. Yes jets are a little more involved but that's just taking out the 8 screws and lifting the whole top off. I mean you are talking about cross threading a jet because its up and down instead of side ways, is that really a concern? Seems like putting them in the bottom of the bowl would be easier. You also mention taking apart linkage, it's 3 little clips and how often are you taking apart a carb anyway?
Again imho a perfectly tuned Holley may be better then a out of the box Edelbrock but honestly how often are Holley's tuned perfect and how often do they stay that way in a boat or car for that matter? If I was drag racing and needed every once Holley would be the way to go. If I want a set and forget carb for a boat or daily driver, Edelbrock. I will lose that 1% out of the box between the two carbs and not have the issue that go with Holley.
On a side note, beside the leaking issues with Holley that are impossible in Edelbrock a Holley D/P weighs almost 4 pounds heavier then a Edelbrock AVS2. Also not saying you should do it but you can convert any Edelbrock auto carb into a marine carb for a couple bucks and a little time.
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Old 08-27-2019, 12:27 PM
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I work on most carbs and many FI's for work and hobby.

I tell people to choose what ever they feel most confident in or what their mechanic is most confident in.
IE: Holley or Weber/Edelbrock/Carter or Quadrajet or TBI or factory/aftermarket multi port or.......

THat said, mild performance motors and up I love Holley carbs. Shhhh, don't let my FI peeps here that. LOL.
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Old 08-27-2019, 01:00 PM
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How about float adjustments? On a holley, very easy, and easy to compensate for varying positions of engines. Edelbrock? Take carb apart and BEND tangs till it has the right level and amount of drop. Then what do you do if the carb isnt level on the boat?

With a holley, you dont need the jet tool, a typical flathead screwdriver will allow you to hold the jet while inserting it. On the edelbrock, you have to drop the jet in the bowl, fish it around and try to get it lined up before threading it in. On some setups, its a pain to have to pretty much lay over the engine to be able to see in there while putting jets in.

If i recall, a 750 cfm holley, will outflow a 750 edelbrock as well. I wanna say edelbrocks cfm ratings were inflated quite a bit.

Todays modern holleys, quick fuels , with billet metering blocks, are a tuners friend imo. Linkage progession changes, accelerator pump tuning is easy, tons of tuning options. I think most people who dislike holleys, never really understood how they function. I just saw a guy on facebook boat group, telling how his holley sucked because the vacuum would drop when he put in gear, and would make the power valve open and foul his plugs. He obviously doesnt understand how the powervalve circuitry works.
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