Holley 12-834 leaking around diaphragm - I tightened the screws but just seemed to make the leak worse. Yanked it out and took it apart and the diaphragm looks to be in good shape but I intended to rebuild it anyway. I thought Holley sold rebuild kits but I couldn't find one on their web site. Anyone know if rebuild kits are available for this fuel pump? thx

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79 Z28 Bought new, honeymoon ride, same wife, same car.

Dump it and buy a different kind of pump. The 6 vane pumps will NEVER seal back up for you once they have started leaking or have been tampered with. You generally have to take them apart to get them to work with the Camaro frame, and there you are. They suck, plain and simple.

yup. I have the Holley 90 or 110gph (don't remember which) and it was OK until I installed the 70-81 camaro bottom plate option, and it leaked. Chucked it in favor of a stock replacement Delco pump specific for a 70 Z28 LT1, and not a hiccup since. Cost $14.00 at NAPA.

Thanks guys - I've been doing some checking and this unit is out the door. I'm going to have to move up a bit since I have a Holley red feeding the mechanical and am now making myself aware of the difference between free flow gpm and gpm under pressure. This entry level system just will not flow enough when I hit the juice. I burned the ground strap off of two plugs when I hit the gas off the line, I don't have a window switch and usually hit the button at 3500rpm. I thought it was because the shift light came on before I hit the 60" mark - in other words I blew the tires, but now I suspect a very lean condition. I do have a retard box (other than the driver) so I don't think it's a timing issue. This was with my old (041) iron heads and have not pushed the blue button since, so I'm kind of looking forward to gettin' on the giggle again.

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79 Z28 Bought new, honeymoon ride, same wife, same car.

I'd just keep the Holley red inline and dump the mechanical all together. There's no reason to have the mechanical there when you have an electric in the line. The mechanical pump is just a restriction to the electric pump. I'd get a bypass regulator and plumb a return line as well. If need be you can always upgrade to a blue/black or a Carter/Mallory pump, etc.

Have thought about that many times - saw a guy at Warner Robins, GA drag strip jump up and down because he let someone talk him into going electric only - and the brand new electric went tango uniform. Same for me, but I just lost the ground and didn't know it till I pulled into the garage and didn't hear the electric humming. My thoughts are, that if properly matched, the two will compliment each other, not hinder. I'm open to suggestions...

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79 Z28 Bought new, honeymoon ride, same wife, same car.

Well, all the mechanical is doing is introducing jitter in your fuel pressure. With an electric only, you have a constant pressure that does not rise/fall rapidly with engine RPM. The mechanical pump has a high/low/high/low whereas the electric has one steady pressure. That alone is worth just using the electric to me for the sake of only not loading and unloading the carburetor needle(s) rapidly at high RPM.

I'm going through a regulator at 6.5psi and have not seen this bouncing. I realize your theory of a diaphragm pump, but with the amount of collected fuel volume between the mechanical pump, filter, regulator, and carburator, I dont think it will be an issue. Realize that when a Holley float unloads, it's inlet valve is going to bounce simply from the motion of the ocean, unless it's on a dyno or a no g-force situation. I'm not running a monster here, about 600hp on a modest juice jet and I can't go much higher because of the rpm intake. The red Holley's flow at 6.5psi is very marginal at that fuel requirement so I'm definitely not going to push the button till I get this sorted out. Thanks for your thought out responses - I'm still open.

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79 Z28 Bought new, honeymoon ride, same wife, same car.

<font face="Arial,Verdana" size="2">Originally posted by CorkyE:
I'm going through a regulator at 6.5psi and have not seen this bouncing. I realize your theory of a diaphragm pump, but with the amount of collected fuel volume between the mechanical pump, filter, regulator, and carburator, I dont think it will be an issue. Realize that when a Holley float unloads, it's inlet valve is going to bounce simply from the motion of the ocean, unless it's on a dyno or a no g-force situation. I'm not running a monster here, about 600hp on a modest juice jet and I can't go much higher because of the rpm intake. The red Holley's flow at 6.5psi is very marginal at that fuel requirement so I'm definitely not going to push the button till I get this sorted out. Thanks for your thought out responses - I'm still open.

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The best way to design a N02 system is with a completely separate fuel system to run the N02 with that you can arm and run when needed. And http://nastyz28.com/ubb/icons/roflmao.gif at the "not a monster" comment with 600 HP on tap with a street-driven car. Hell, even a track-only car, 600 HP is nothing to scoff at. http://www.nastyz28.com/ubb/smile.gif

Dump it and buy a different kind of pump. The 6 vane pumps will NEVER seal back up for you once they have started leaking or have been tampered with. You generally have to take them apart to get them to work with the Camaro frame, and there you are. They suck, plain and simple.

I was just reading through some old posts and saw this.

They will seal correctly as long as you don't over torque them. The top portion will bend easily at the bolt holes. You can take the pump apart and lay that piece on a flat surface. Then take a flat hammer and tap it out. You will be able to get it close enough that a file can do the rest. Reassemble the pump with the allen head bolts being torqued in sequence. Torque it just enough to barely compress the gasket. It shouldn't leak again.

The main mistake I have seen people make with these is to use plumbing supply store style 90o fittings. They will cavitate really bad with these pumps. Especially on the inlet side. I made this mistake myself. When I switched to full flow aircraft fittings it made a huge difference.

With our Camaros you will need the bottom feed kit. I ran my inlet from the bottom of this plate. I ran the outlet from the original spot on the side of the pump. This routed the fuel lines nicely around all the obstacles.

Great news'!!! I just bought the holley pump you speak of and had to move the bottom around, doe'snt leak yet. I'm going out to look again at it. and I had to use the 90 fitting , where do I get those aircraft fittings ?

Russel, Earls, and Summit brands are available. Here is a picture of them.http://cgi.ebay.com/ebaymotors/HUGE-UNBELIEVABLE-222-AN-FITTING-LOT-PLUS-BRAIDED-LINE_W0QQitemZ280013906013QQihZ018QQcategoryZ133199QQrdZ1QQcmdZViewItem

The original thread was talking about a Holley 12-834 which is the 80 gpm. I run this pump and didn't have to do anything to it for it to work on my car. No special bottom plate or rotation of the housing and no issues at all. Just wondering why other people had to change things for it to work for them?

The original thread was talking about a Holley 12-834 which is the 80 gpm. I run this pump and didn't have to do anything to it for it to work on my car. No special bottom plate or rotation of the housing and no issues at all. Just wondering why other people had to change things for it to work for them?

B/C we got off the "topic" of the 12-834. I put the larger pump on and had to clock the bottom.