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Discussion Starter #1
I've got some carb issues. Last year I bought a rebuilt Holley 750 DP (list 9379) from a builder on Ebay (I know....I know) and can't return it, nothing but problems with this guy. I paid him a little extra for what he called a 'stage 2' carb (whatever that means). When I finally put it on my engine (stock 460 BBF), I put fuel to it and gas started pouring out of the vent tubes into the bowls. I pulled the sight plugs and have been trying to adjust the floats, but I've got them cranked so far clockwise that the adjustment (in the fuel bowl) is now below the adjustment nut, but the fuel is still too high. I've got those nitrophyl floats too. Also, I'm guessing I'm gonna have issues with idle mixture screws (I have four of them), how do you adjust those? Thanks in advance for the help.
 

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Discussion Starter #2
I took both bowls off and when I flipped them upside down (read it on a previous post here), the float barely even moves (stays towards bottom of the bowl. I have full adjustment (I tried it while I had the bowls off) but the floats just aren't keeping fuel from coming. BTW I have an electric fuel pump with a regulator and my gauge says 4psi. This is the same pump/reguator that I used last year, before I tore the motor down, and they were fine.
 

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Fuel is getting by the needle/seat or the small O ring that seals the needle/seat assembly. Try changing it or at least remove it and make sure there is no debris in the seat and check the O ring for cracks, hardness, flattening. It should be plyable, round and in one piece....Easier just to change them and when you do put a little bit of grease on the O ring and install carefully.
 

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yeah what he said :)
 

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Discussion Starter #5
Fuel is getting by the needle/seat or the small O ring that seals the needle/seat assembly. Try changing it or at least remove it and make sure there is no debris in the seat and check the O ring for cracks, hardness, flattening. It should be plyable, round and in one piece....Easier just to change them and when you do put a little bit of grease on the O ring and install carefully.
How do get to that o ring? I pulled the float bowls off earlier and removed the two screws inside, thinking that was where I needed to be but I couldn't remove the float. Is this where I need to go? Or do I pull the adjust ment out of the top? Also, I just figured out that my secondary accelerator pump won't squirt gas. When there's gas in the carb the secondaries were REAL TIGHT, so I traced the problem to the accelerator pump (secondary side). It seems clogged somewhere between the pump and the little nozzle that squirts. I moved the little bb in the pump and gas will go in the hole, and I removed the nozzle on the top of the carb and it's all dry. Where's a good place to start with that problem? Man I will never buy anything on Ebay again....I promise!!!!!!:|err
 

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steelcomp was here
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The needles and seats come out of the top of the float bowl where the adjusters are. If you've screwed them down too far, you might have to remove the nut, and just install the screw in the top of the needle and seat, and pull it out that way. The o-ring is on the needle and seat. Definately getting fuel past the needle and seat somehow. Sounds like you just need to buy a kit for the carb and go through it. It's a little complicated the first time around, but Holleys are as simple as it gets, and there's enough help here to get you through it. Just take the carb as far apart as you can keeping track of where things go, so you can re-assemble it. (Unfortunately there's no guarantee it's even been put together correctly if someone else has had it apart) Use compressed air and blow out all the passages...every teeny little hole from both directions, and then you can re-assemble with new gaskets and needle and seat assemblies. If the carb is dirty, you can use spray carb cleaner or some solvent and a brush, and rinse with warm water, then the compressed air.
 

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I was having issue's with the float's once and come to find out the adjuster hand bottomed out and collapased in the top of the float. It was bottomed out and therefore was out of adjustment. Check yours to make sure the same thing isn't happening.

Sleeper CP :D
 

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Discussion Starter #8
Well.....one problem fixed. I pulled the valve/seat assembly out and there was some crap/dirt on the needle (primary and secondary). cleaned it off, but I pulled the bowls just to make sure I got it all too. I saw on this forum that you can adjust them to be close by holding the bowl upside down. I did that but I had to bend the tabs on both floats to give me some room for 'adjustment'. OK....now I've got the problem with the secondary accelerator pump not squirting. It works good at the bowl, but something isn't letting it get to the squirter. After I pulled the squiter out, it looks like there a screw (pointing up), do I have to pull the base off of the carb to get to it? I know I probably should just rebuild this thing (again), but I'm kind of wanting to go out tomorrow so I'd just like to fix this problem. Any ideas how to best unplug this? Thanks for all the help so far.
 

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steelcomp was here
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There's no screw under there. There is a small check valve under the discharge nozzle (squirter). It looks like a little missle...it's steel, and round, and pointed on one end. The pointed end should face down. This thing should just fall out in your hand when you turn the carb upside down. If it dosen't, it's stuck, and probably the reason your squirter isn't working.
 

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Or Seth, either one
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It's been a while since I've delved into a Holley so I could be incorrect. But, isn't it possible the wrong gasket has been used on the metering block/plate which would block that passage? I seem to recall reading something about that in the rebuild kit directions. Maybe it was a dream???

Just thought I'd throw it out there. Good luck!

-Seth-
 

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It's been a while since I've delved into a Holley so I could be incorrect. But, isn't it possible the wrong gasket has been used on the metering block/plate which would block that passage? I seem to recall reading something about that in the rebuild kit directions. Maybe it was a dream???

Just thought I'd throw it out there. Good luck!

-Seth-
Yes, some of the bowl gaskets came with the accel pump passage on one side only. Because these gaskets can go on in any direction (except upside down) this could be the problem also if nothing is found in the check valve area that Steel mentioned.
If you push down on the accel pump arm and it is stiff and doesn't want to move, there is a blockage somewere (stuck check valve or gasket backwards as described above). If it moves freely but doesn't pump anything the one way flapper in the accel pump well may have been left out or is damaged thus allowing the fuel to be pumped directly back into the bowl instead of out the nozzle.
 

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Discussion Starter #16
It's been a while since I've delved into a Holley so I could be incorrect. But, isn't it possible the wrong gasket has been used on the metering block/plate which would block that passage? I seem to recall reading something about that in the rebuild kit directions. Maybe it was a dream???

Just thought I'd throw it out there. Good luck!

-Seth-
Yes, some of the bowl gaskets came with the accel pump passage on one side only. Because these gaskets can go on in any direction (except upside down) this could be the problem also if nothing is found in the check valve area that Steel mentioned.
If you push down on the accel pump arm and it is stiff and doesn't want to move, there is a blockage somewere (stuck check valve or gasket backwards as described above). If it moves freely but doesn't pump anything the one way flapper in the accel pump well may have been left out or is damaged thus allowing the fuel to be pumped directly back into the bowl instead of out the nozzle.
I never thought to check that. I'm gonna pull the bowl again and double check that all of the passages are open. The pump itself seems to be good, when I had the bowl off it would pump air into the bowl just like the primary side did. I even switched the pumps and diaphrams and have the same problem on the secondary side. Also, what is the best way to set the four corner idle screws? I got it started yesterday by putting them all at 1 1/2 turns out. When that idiot sent me the carb he had them set 3 turns out. It seems to run pretty good, but I'm guessing there's a way to 'fine tune' it and I know you guys will know. Thanks again. :)hand
 

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steelcomp was here
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The AFR screws are kind of an "ear" thing. Some guys use a vac. gauge and adjust for the highest vacuum. Personally, I just start at 1 1/2 turns, and screw each one out until the idle starts to drop off or get a little rough, then back in until the same thing happens. If everything is right with the carb, there will be a sweet spot in the adjustment where the idle quality is best. Do that with all four and you should be set. If you move the screws in or out and there's no change, there's other issues to address.

I haven't seen a bowl gasket with only one acc pump hole in a long time, but that's not to say it's not possible. One other thing that is possible is that on the old spread bore 4175 style carbs, the metering block had a transfer tube for the acc pump into the main body. That metering block gasket has a large hole in the center to allow for the tube. I'm not even sure if it would interchange, but if this gasket is used on a 4150/60 style carb, the gas will just discharge into the PV relief in the main body and never continue through the transfer port. It's a little hard to understand by explanation, but you'll see. The acc pump passage goes from the metering block to the main body right above the power valve. If the hole in the gasket is bigger than the hole in the metering block, it'll be obvious that it's not sealing by looking at it. (We're talking what should be a hole about 1/8" in dia. vs. a cut out in the gasket about 3/8" wide)

One more thing...you can put your finger over the hole in the bottom of the float bowl and pump the acc pump arm. You should be able to build some pressure against your finger if the diaphragm or check valve is doing it's job.
 

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I've got some carb issues. Last year I bought a rebuilt Holley 750 DP (list 9379) from a builder on Ebay (I know....I know) and can't return it, nothing but problems with this guy. I paid him a little extra for what he called a 'stage 2' carb (whatever that means). When I finally put it on my engine (stock 460 BBF), I put fuel to it and gas started pouring out of the vent tubes into the bowls. I pulled the sight plugs and have been trying to adjust the floats, but I've got them cranked so far clockwise that the adjustment (in the fuel bowl) is now below the adjustment nut, but the fuel is still too high. I've got those nitrophyl floats too. Also, I'm guessing I'm gonna have issues with idle mixture screws (I have four of them), how do you adjust those? Thanks in advance for the help.
Do your'e self a favor. Before you go cutting holes here and there,Take the bowls off and clean everything with carb spray,check the acc. pumps cause they are probably stuck. needle and seat are so other things have found a home and are staying for the night. Under the squirters is the needle check valve which will also stick. From what I gather these carbs have probable sat for a while(DRY) and the stuff needs alittle clean and lube. IMO M
 

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Discussion Starter #19
Found the problem. It's not a gasket blocking the fuel, but there's a clog in the metering block itself. I can actually see where the fuel travels from the small hole in the bowl into one side of the metering block then through it and out the other side. Except I can't get it to open up. I know this is it because I can't get carb spray to travel through it. I checked the accelerator pump and the carb body (to the squirter) and they flow good. Guess I'm gonna try soaking the metering block in carb cleaner then use compressed air like someone told me here. Thanks for all the help. :)devil
 

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steelcomp was here
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Found the problem. It's not a gasket blocking the fuel, but there's a clog in the metering block itself. I can actually see where the fuel travels from the small hole in the bowl into one side of the metering block then through it and out the other side. Except I can't get it to open up. I know this is it because I can't get carb spray to travel through it. I checked the accelerator pump and the carb body (to the squirter) and they flow good. Guess I'm gonna try soaking the metering block in carb cleaner then use compressed air like someone told me here. Thanks for all the help. :)devil
Compressed air is your best friend when it comes to carbs. Glad you found the culprit.
 
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