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Holly 9510 float adjustment help needed |
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CaptDH 
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 Topic: Holly 9510 float adjustment help neededPosted: August-10-2023 at 1:02pm |
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Getting a bit of extra fuel dumping while at rest after a run. Starts are difficult (probably flooded) Can anyone point me to a good tutorial or any other tricks for this carb? Also, is the 9510 also named something different?
Has front and rear brass float adjusters. Thanks |
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KENO
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Posted: August-10-2023 at 2:17pm |
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The 9510 is part of the Ford part number for your Holley. It tells you that it's a carburetor in their parts system.
If you look at the air horn on the carburetor you'll find the Holley list number. Here's a typical picture  Sometimes it says list in front of the number, sometimes it doesn't. This one is a Holley 4160 and the list number (50419-1) identifies it as one of the bazillion or so different versions of a 4160 that Holley built. Yours is probably a Holley 4160, but you can look up the list number or post it here and somebody will tell you what it is. Not knowing any of the background/history of the carburetor, you may have junk between the needle and seat causing the overflowing and float adjustments won't help that, but a good cleaning and or new needle and seat assemblies might. So.............more info needed
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CaptDH
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Posted: August-10-2023 at 8:44pm |
 Attached photos of the numbers and carb. Pulled the needles and cleaned / blew out with a carb dip.Still had difficulty starting after nearly getting swamped by a surf boat. Could use advice on how to move forward. Part numbers for the needles, etc. Thanks…. DH
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CaptDH
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Posted: August-10-2023 at 8:47pm |
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Image on the float needles. I know the different types and these are the long thin barrel type. Where can I order a set?
Thanks again DH  D2JL-9510-C
List 6407 49 |
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MrMcD
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Posted: August-11-2023 at 2:19am |
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Any local speed shop if you have one near you, Summit Racing or Jegs should have it them also. Maybe even Amazon if you have part numbers and jet sizes.
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KENO
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Posted: August-11-2023 at 7:39am |
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Your 6407 is a 450 cfm Holley marine carburetor from the early to mid 70's.used on 302 Fords from numerous different marinizers like Mercruiser, Volvo Penta, Waukesha, PCM and others
The early ones like yours had externally adjustable floats and had no J tubes on the bowl vents, just straight tubes sticking up like in your picture. The J tubes came along in the later 70's and can be retrofitted. They make sure any overflow out the tubes goes down the carburetor throats into the engine and doesn't spill outward onto the manifold where it can cause fires, explosions etc.
The best thing you could do would be to buy a Holley 703-1 Renew Kit for it. It'll have all the parts you need for a rebuild plus a few extra parts for different versions of Marine Holleys It'll have the needle and seat assemblies for both bowls and all the gaskets you need, since you're bound to destroy a gasket or 2 or 3 taking things apart. |
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KENO
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Posted: August-11-2023 at 7:46am |
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You can find lots of YouTube videos on rebuilding/cleaning Holley 4160's.
You want to find one that deals with externally adjustable floats like you have and not the internally adjustable ones. Things like the needle and seat assemblies and the floats themselves don't interchange between the 2 different styles You can also find different books on rebuilding Holley's, just full of pictures and step by step directions. One of these books will be the best 25 bucks or so that you could spend. Almost forgot, you wanted advice................stay away from thirf boats
and the rest of the advice would be to go through the whole carburetor with the renew kit. |
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CaptDH
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Posted: August-11-2023 at 9:02am |
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Thanks guys. I have rebuilt carbs before but on WWII Willys and motorcycles. This is my first run at a 4 barrel.
I am seeing zero markings on these. Do we have a part # suggestion for replacing?
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KENO
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Posted: August-11-2023 at 9:24am |
Holley part number is 6-506, about 20 bucks each.................or the renew kit mentioned above with all kinds of other parts needed for 60 bucks. Or you can cross reference those numbers to other companies needle and seats or rebuild/renew kits at a variety of prices So..............what's this engine and what's it in
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91NaughtyQ
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Posted: August-11-2023 at 9:45am |
You will have no trouble. I rebuilt mine with no carb rebuilding experience. If you have experience it should be no problem.
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1991 Ski Nautique
(Previous)1984 Ski Nautique 2001 |
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CaptDH
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Posted: August-11-2023 at 9:45am |
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Ford 302. 76 CCraft
Looks like it is an automotive carb so guessing the rebuild kit is the way to go if I decide to do some investigating. DH |
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CaptDH
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Posted: August-11-2023 at 11:47am |
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Can anyone verify the Holley 6-506 will replace what I have here? Again, this is an automotive carb and the appear quite different. Mine has an o ring under he nut. Looks like I can switch to the other style with the needle seat hardware kit.
Pn 34-7 DH  |
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KENO
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Posted: August-11-2023 at 12:17pm |
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If you unscrew the nut at the top of yours, it'll look a lot more like the Holley 6-506 and it should screw onto the 6-506 and the 6-506 will screw into the bowl. They've had some design changes over the years but still interchange.
That number comes from Holley's listing of what fits a 6407 carburetor Now whether yours is all original that might be a different question. And your carburetor is a Marine certified Holley that started life as an automotive carburetor with a few changes to meet USCG regulations. I don't usually yell but in this case...............BUY THE RENEW KIT That way you can get into the carburetor without worrying about ripping gaskets that like to rip when you take things apart, you'll have everything you need
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CaptDH
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Posted: August-11-2023 at 12:23pm |
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I plan to get the Renew kit. Just wanted to verify those seats were interchangable. Here is what I gathered..
Mine uses the set screw to adjust the needle and other uses the nut. Different mechanism doing the same thing. Adjusting pressure to bowl. Thanks……
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KENO
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Posted: August-11-2023 at 12:36pm |
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You should have the needle and seat assembly, the nut, a flat topped screw and a couple of gaskets. You'd need the 34-7 kit you mentioned above if you don't have those parts now. They come in the 703-1 kit so no need to order separately.
I can put a picture here in a little while PS check your PM inbox |
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KENO
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Posted: August-11-2023 at 1:46pm |
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Here are the parts associated with the externally adjustable needle and seat, and they're all in the 703-1 kit 
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CaptDH
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Posted: August-15-2023 at 8:19pm |
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Received the Holley restoration kit listed above. The included needle and seats were installed and all other parts remained the same except for some of the new gaskets and a good cleaning. Here is a video of the incredibly rich running. Couldn’t do anything with the needles to get it to run smooth. Stalls out as soon as the power is pulled ( shown in video ).
Put the old style seats in and immediately felt closer to normal but the flooded engine stopped the testing for the day. Could really use some advice as I am running out of days off to tackle this. PO said the choke could be the issue. Did not notice if they were open so will look in to that too. |
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KENO
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Posted: August-16-2023 at 6:44am |
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Is it flooding from the primary side or secondary side or you're not sure?
One way to make it run really rich is to use the wrong primary metering block gasket. Holley gives you 2 similar but different gaskets in the kit for different applications. They look like the picture below  Your carburetor has a metering block that uses the gasket on the bottom with the small hole above the cutout for the power valve If you used the one on the top, you'll have a really rich running engine. So, check your leftover parts collection to see which one went into the carburetor |
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KENO
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Posted: August-16-2023 at 7:17am |
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After watching your video, I think you should have the guy you bought the boat from, give you back about a hundred bucks so you can get a marine fuel pump for it
It's a safety thing. It has nothing to do with your current problem, but if the diaphragm ruptures it'll be spraying gas around in the bilge near hot exhaust manifolds and things that spark He was nice enough to put a marine Mallory distributor on it for you though, so thank him for that.
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CaptDH
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Posted: August-16-2023 at 9:04am |
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Excellent find Keno. Swapped it out. Also noticed the original power valve is a 9.5.
Kit came with a 2.5 and 7.5. Should I swap it for one of those as a start? Will test with vacuum but wanted to check for best starting point while it’s on the bench. DH |
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KENO
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Posted: August-16-2023 at 11:23am |
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It came with a 8.5 power valve originally and #58 main jets.
Since you don't have an 8.5, I'd probably put in the new 7.5 since it's new and shouldn't have any leakage issues of it's own and give things a whirl with the swapped gasket and new power valve Holley renew kits are kinda all over the place with their power valves for whatever reason. Safe to assume that you blew out every passage you could find with cleaner and compressed air?
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CaptDH wrote: