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Holley Carb Adjustment
https://slantsix.org/forum/viewtopic.php?t=45791		 Page 1 of 1
Author:  63dartdude [ Mon Aug 01, 2011 1:35 pm ]
Post subject:  Holley Carb Adjustment
I have a Holley 500CFM carb on my car. I read up about this adjustment:

The first adjustment to check is the clearance between the pump

operating lever and the pump diaphragm cover’s arm, at wide

open throttle. This clearance should be around .015". The purpose

for this clearance is to assure that the pump diaphragm is

never stretched to its maximum limit at wide open throttle.


Color me stupid. If I understand this correctly, the arm that is touching the cam has the spring adjustor on it. The gap I should be checking is between it, and the pump diapragm arm. Here is where I get lost.

If I have it at WOT, one arm is pushing the other arm with force. I have adjusted that spring every which way possible. It is like pushing a shovel under the car tire. I don't get it. How do I adjust for that .015?
Author:  Dart270 [ Mon Aug 01, 2011 1:50 pm ]
Post subject: 
Clearance is 0.015" at idle position, not WOT...

Lou
Author:  63dartdude [ Mon Aug 01, 2011 2:38 pm ]
Post subject: 
Thanks. I will try that. That sure makes a lot more sense. But I read WOT from a couple sites.
Author:  DusterIdiot [ Mon Aug 01, 2011 5:55 pm ]
Post subject:  Wot
Gonna have to edit Lou's response that qualifier is from WOT:

Here's the quote boggarted from Holley's site:
Quote:
QUESTION My vehicle has a stumble from a dead stop. What can I do to cure this?
ANSWER The most common cause of a stumble is not having an adequate accelerator pump shot. The first thing to do is to look at the discharge nozzle and make sure you are getting a good strong pump shot. If not then you need to inspect the pump diaphram for a hole or tear. You will also need to make sure that the pump passage is clear from any trash or debris. First you will need to check the adjustment on the pump. To do this you will open the throttle all the way (WOT). Push the pump arm lever down and then adjust the pump override spring to obtain .015" clearance between the pump arm and lever. If you are having a stumble and no black smoke out the tailpipe then you will need to increase the shooter size. If it stumbles and you are getting black smoke from the tailpipe then it will be nessasary to decrease the shooter size
-D.Idiot
Author:  63dartdude [ Mon Aug 01, 2011 6:33 pm ]
Post subject: 
The IDLE setup didn't change anything. First off, I don't get a stumble taking off. I can drive the car down the driveway, and come up the steep driveway. Under 2500 rpms, it runs fine. Taking off and getting a stumble was when I moved the cam number to 2. Putting it back to 1, it takes off fine. As I sit and watch the tach, I slowly rev up the engine, and as soon as it hits around 2500rpms, it starts stumbling.

OKAY, I am finally getting the picture. Once I have it at WOT, then do the adjustment - duh.... I will give that a shot. Thanks.
Author:  ceej [ Mon Aug 01, 2011 7:00 pm ]
Post subject: 
The Holley 500 makes a lousy street carb. You can chase the dead spot around, but you can't get rid of it. All the circuits need to be bandaided in some way to get it to run in a passable manner. Somewhere in the mid-range, it will stumble. A 500 should only be used for a strip car. It's too dang big for street use. You would be better off with a 600 Holley four barrel for driving. It will deliver better economy anyway. To make a 500 steetable, custom air bleeds are going to be necessary, and I don't know that you'll ever nail it. :roll:
But boy does it make a slant leave hard! :lol:

2¢

CJ
Author:  63dartdude [ Tue Aug 02, 2011 7:10 am ]
Post subject: 
Thanks Ceej. Nice hearing from you.

I bought this carb off a daily driver, with a stock engine, where it was running fine.

Here is my setup.

Pertronix II ignition
Offy quad intake manifold
Clifford headers
Compression on head - well, since I have owned the car, the head has been milled . 091. For sure it had to be milled before I owned the car. So I think it is safe to say it is at least 9.0.
Holley 2300 CFM with a brown cam and 50cc pump. That sits atop of two adapters, to fit on the OFFY, giving over an inch of spacer.

I was thinking with all that extra air space, the 500 would be okay.
Author:  ceej [ Tue Aug 02, 2011 4:36 pm ]
Post subject: 
Even the guys running 300 Fords have a hassle getting the 500 to work right. I'm sure it can be done, just haven't taken the time to figure it out.

The 50cc pump is a must with those Silver Dollars you have for throttle plates!

It's the mid-range cruise and cruise to power transition that will be a bear. If somebody already had it set up to run correctly on a small displacement engine, make sure nothing was changed, like power valve value or jet, then make small changes to that setup. I take it you rebuilt the carb after taking ownership.
The check & weight for the shooter is the same? Any air bleeds modified? small pieces of wire are sometimes inserted into emulsion passages to control how the bleeds work. If there were things like that done, make sure they are still there.
Other mods can be removable air bleed control jets. Lots of things have to be just right. If your engine has different vacuum characteristics, the setup that worked on the other engine may not behave the same on yours. If it was stock, it was a Herculean effort to get it to run right.
This is not a progressive, but a 2300, right?

2¢
CJ
Author:  63dartdude [ Tue Aug 02, 2011 4:55 pm ]
Post subject: 
No, I didn't rebuild it, since it was working okay on his car. I emailed him to get more info on his setup. I heard that brown cam is really what shoots more fuel than I need, and a pink cam will cut that down some.

And I forgot to mention the oversized valves in the head.
Author:  ceej [ Wed Aug 03, 2011 6:04 am ]
Post subject: 
You want a bunch of pump shot. Don't put a pink pump cam on it. It'll fall on it's face.
What shooter is in it?

CJ
Author:  63dartdude [ Wed Aug 03, 2011 7:51 am ]
Post subject: 
I don't know what shooter is in it. Still doing other testing today. I also forgot to mention the dizzy is recurved as well. As for the shooter, I don't know what size it is. I may have to tear it all apart later this week. If so, I will report what it is. Thanks.

And I haven't gotten the pink cam yet.
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