Holley 1904 Economizer/Power Valve Delete

[60s Refugee]

My two 1904's are sitting in the carb cleaner/dip waiting for me to get started on the rebuild tomorrow. These will be my Alpha and Charlie carbs until I can get better ones. I was reading a previous post where a forum contributor removed the economizer valves and cut a gasket to block off the passage (for the outer carbs only). My question is, why do this and what is the benefit? I need to find out 'cuz tomorrow I reassemble the carbs. These carbs have already had the entire choke assy removed (even the butterfly and shaft). The SCV passages, choke draft and choke rod holes have been blocked, and the accelerator pump arms are unhooked.

I bought rebuild kits from Auto Zone. These are GP Sorenzen kits and look pretty good. They fit 1904 and 1960 models. They include new economizer valves. There are more parts in the kit than I need from the looks of it.

It was also mentioned in that post that the choke rod and butterfly act as a diffuser for the air flow? What's up with that?

Thanks
Harry

 

[jahearne]

I chose to go that route because from what I understand, the outer carbs with progressive linkage are just there to dump fuel. Economizer = Power valve. Offy instructions say nothing about them. The powervalve works on vacuum. At idle/cruise there's enough vacuum to overcome the tension on the spring keeping the powervalve closed. Under load like climbing a hill, the vacuum drops, opening the economizer allowing more fuel into the mains enrichening the circuit. You adjust them by changing the tension of the spring. Since these carbs are basically two vacuum leaks at idle I decided to leave them out.

I've been meaning to play around with them, but I've never had the chance to replace them to see if I get better performance. Heck, I haven't the chance to put an A/F meter on it yet. But it runs good without the outer economizer valves. If I did get better performance, I'd bet that larger main jets would do the same thing. I get no hesitation climbing hills, cruising or WOT throttle. I do get a slight hesitation when I crack open outer carbs around 3k rpm, but not when I gradually open them up from a lower rpm nor when I stomp WOT. I do have a crappy idle that I haven't been unable to fix even with the outer idle circuits cracked open. More top-end would be nice.

Quote from Holley Service manual:
"Airstream turbulence over the distribution pin and choke plate distributes the fuel over the lower portion of the choke plate where it is vaporized and mixed with the air flowing through the carburetor. The throttle plate controls the amount of fuel-air mixture admitted to the intake manifold, regulating the engine speed and power output in accordance with accelerator pedal movement. The distribution pin extending perpendicularly from both sides of the choke plate creates a turbulence as an aid to the proper distribution of the mixture to all cylinders"

http://www.oldcarmanualproject.com/manu ... /index.htm

I don't recommend leaving the choke out.

On step 13 page 21 & 22 of Holley Manual when assembling the main well to carb body. I install the accelerator pump cam so you don’t have to hold your “thumb over the protruding end of the pump rod sleeveâ€￾ to prevent the diaphragm from distorting due to spring pressure. Then when asked to “release the pump rod sleeveâ€￾, I engaged the pump cam to mimic the natural travel of the accelerator pump then fully tighten the screws.

Hope that helps,

 

[60s Refugee]

Good idea about that pump cam. The piston was stuck in the hole when I took it apart.

The elimination of the economizer makes sense too.

Too bad the previous owner of the carb discarded the choke butterflys and rods. I'll just hafta' try it without them.

Harry

 

[60s Refugee]

jahearne,

I decided to plug the passages on the economizer with RTV. I forced some down the hole in the carb and through the passage in the cover. This should close it up as well as a gasket would, I think.

Now that it's together I have a really fast idle problem. I have posted a new thread about that. I set my float heigth at the recommended 9/32" and that seems to be enough, there isn't any leakage.

Harry

 

[jahearne]

I saw your post and figured Bort had the right idea. When I had that problem the linkage was hitting on the Offy manifold. I can't get the darn thing to idle properly anyhow, so my idle is a bit high to begin with.

The RTV will eventually disolve with gasoline, but it'll just get sucked into the motor but create an internal vacuum leak. You can get some lead fishing wieghts and pound them into the holes. I used the gasket in case I wanted to change carbs in the future I could easily replace the powervalve.

I have extra Holley parts and might have spare chokes. I really don't know what difference it might make with out them. I'd imagine it might make a big difference at low rpm, but since the outer carbs kick in at 1/2 to 2/3s throttle it might not make a difference.

I had a terrible time setting the float level. I used glass bowls and did it by sight. When I set them according to the float gauge that came with the kit, it flooded. I also have to use a pressure regulator. One of my carbs will have a high float level without it; the level is high but it doesn't pour out anywhere. If it wasn't for the glass bowls I'd be having all kinds of trouble trying to figure what's going on.

 

[60s Refugee]

So, the floats must be level to close? Both needles seem to be closed OK. They didn't before I rebuilt them. When inverted the floats look more or less level. Wish I had some clear covers. I have noticed that the two outers act differently too. The rear carb runs higher on the sync gauge and is effected nore noticibly by idle screw adjustment. Also, with c carb, (and c only) when the air filter is set in place the engine idle speeds up some!

Harry

 

[jahearne]

Yup, 1904 are a pain. They are large vacuum leaks. Need open the idle mixture screw a bit to compensate and use the idle stop screws to sync them up.

I have no idea where the floats have to be when inverted. I basically eyeballed them with glass bowls and an electric fuel pump until I got them right. The glass bowls show up on eBay from time to time. Search for Holley 1904, Holley glass, Falcon carb, Holly (mispelled on purpose) and you can find crusty glass bowled carbs for >$25. They clean up brand new with a bit of steel wool. See our other post. I left a more detailed post. Sorry I didn't get you your PM sooner. Work gets in the way even though I'm on computer all day.