Some of these carbs shipped with the wrong diaphragm. I'm pretty sure on a vac Secondaries carb, there's no acc pump to squirt anything into the secondaries.

 

Yes no pump. When I work the seconds I can hear the vacuum diaphragm doing it's job. I hoped it might at least give me some "mist" so I knew fuel was flowing....

 

Does the secondary gasket have the window for a power valve for a SA carb or is it the gasket with no window ?

 

I don't know the answer to this one,

Take the list number and look on the Holley site, they have all the carbs listed per list number and all the repair parts listed for each carb.

Neal

 

Oh ? Hadn't seen that I guess I gave up after years of manuals saying something like " install the gasket" and not mentioning up, down, back, front, whatever. They show details of each part ? Thanks....not so good with computer searches here on my end....sorry.

 

Dug out some old gaskets. The windowless ones won't fit.

 

I'm now placing bets on a pinhole in the diaphragm...

 

I found a tiny crack in the diaphragm near the screw that cannot be accessed without removing the electric choke. I revise my earlier statement.....did not COMPLETELY take it down after the first time and missed this leak.....

 

Is the crack in the vacuum secondary diaphragm?

This may be it, give it a try and let us know if it takes care of the issue.

I was going to say that if the secondary was opening and there was no fuel flowing there would be a huge flat spot and it would more than likely nose dive.

The other thing that I would check if the diaphragm don't fix it is to check the bowl were the needle and seat goes, you may have a casting issue where the O-ring seats and the sealing area is compromised. The bowl is the only common item that you have not changed other than the gaskets. You may be able to look down in there with a light and see it there are any issues.

The bowl should not fill past the point it is adjusted to.

Did the new needle and seat come with a new O-ring?

Link to Holley's list numbers and parts:
http://www.holley.com/data/TechServi...%20Listing.pdf


Neal

 

If you are having trouble with the fuel level in the rear bowl, it is unrelated to any problems you may be having with fuel flow OUT of the bowl. The needle and seat should shut fuel off as soon as the float reaches the proper level, regardless of whether fuel is flowing into the secondaries or not. The problem lies there, the float may not be rising with the fuel, the needle and seat may not be sealing, the float may be touching the metering block before it reaches full height, who know what else? Take the bowl off, and set the float level dry, make sure the needle is sealing against the seat while the float is in the proper place. Make sure the float tang isn't all tweaked out of shape and allowing the float to hang up on something.

If you take a piece of pipecleaner, or bread bag sealing wire, or whatever, and wrap it around the rod that comes down from the diaphram and actually works the secondaries, it will give a "telltale" as to whether or not your secondaries are opening, and how much. If all you've ever dealt with are double pumpers, it may be something you are unfamiliar with. On a vacuum secondary, the diaphram senses the amount of airflow thru the primaries, and opens the secondaries accordingly. It does it in such a way that there needs to be some load on the engine in order for them to work, so you need to actually take it for a spin, not just wing it up to 6 grand in the driveway. And if your secondaries are opening up wide, and no fuel is being provided, I would think that you would be able to feel that as it suddenly goes lean. Way lean.

You really should be able to hold the metering block gasket up to the main body and the metering block and see if all the holes line up visually.


Scott

 

Rob and Scott. Thanks for the continued help. You guys are now seeing why im a liitle tweaked on this one. When I take the bowl off and set the fuel level all seems perfect.

When I start the car it idles fine and the level is perfect.

Then when I drive the car through a full throttle run it performs well

After when I check the level the level is too high and will not return lower even after continued runs.

So I was then feeling that the seat was holding as no fuel level creep happens at idle.

New fuel pump should have good pressure.

Your point about the float making contact is a good one. Maybe it originally had a plastic float and now has a brass....different dimensions ?

The gaskets can be universal but it appears the extra holes are not causing issues.

O ring is new and soft on the needle/seat....I will definitely check for a boogered bowl fitting though....thanks.


I think I now see why this was such a deal on eBay.....

 

There's is no doubt I got frustrated on this one and missed some things. My insomnia proved beneficial for once.....I sat and played with it for a while and discovered three issues.

Small crack or tear in the rubber diaphragm near the screw hole closest tom the main body

The float tang was bent just enough that when I adjusted the float level the o ring was seating right at the edge of the bowl flange and allowing fuel to get by

The needle seems a little sticky and there is a slight delay when pressure is applied before it seals.

Ha. Now to see if I can find a new diapraghm without resorting to mail order.....!

 

Yeah, I know the feeling of looking at something and saying "There's nothing wrong with this thing, it should just work!!!" and scratching my head over it, and then suddenly the light bulb goes off. "Of course, why didn't I see it before....".
I'm kinda the opposite of you, all the Holley carbs I've ever dealt with were vacuum secondaries. As far as I can tell, the secondaries on a double pumper work pretty much the same as the primaries, but vacuum secondaries are a little different. The main tuning device is the spring in the secondary diaphram, it controlls the rate at which the secondaries open. The conventional wisdom is to keep installing lighter springs till it bogs from opening to quickly, then go back to the last spring before that one. Good luck,


Scott

 

Thanks Scott. I have the kit. Currently using the purple spring.....wish I could make my own springs.....