455 with Howard roller 555/565 currently running a 750 vacuum Holley but it is running pig rich at idle I have checked everything I know running 14 degrees timing transfer slots square 6.5 over with 13 inch of vacuum no leaking a fuel level at bottom of site hole any suggestions would help plugs are black

 

What distributor are you using? If an HEI you need more timing.

 

How do you know how much total he has etc.? How much? Where in the rpm range?
To make a general statement like this is irresponsible and short sighted.
How about asking about the other parameters of his tune?
Op- you should be able to open the rear throttle plates a bit, depending on what model/year carb it is. I’d start there, as well as making sure you’re not pulling fuel from the boosters.

 

Maybe check the power valve? Long ago I read that a backfire could rupture the diaphragm and cause excessively rich condition.

 

Need more information. Exactly which Holley ? What is your ignition setup ?

 

Did you properly tune the carburetor? I don't know the cam specs but a likely cause of pig at idle is the power valve is open at idle. google search Holly Carb power valve sizes for more info.

AI Overview
Select a Holley power valve by measuring your engine's manifold vacuum at idle (in gear for automatics) and dividing by two. The goal is a valve that stays closed at idle but opens under load, with 4.5, 5.5, or 6.5 Hg being the most common sizes for street applications.

 

Pig-rich condition is not unique to Holleys, but I had trouble with that in the 80’s. Eventually I went to late 70’s 170-series 800 CFM quadrajets and stayed there.

Decades ago I used Holleys, they work just fine, but like any carb will need some tuning of the jets, power valve and vacuum secondary spring if you’re going to get them to work right.

You can bench test the power valve by putting vacuum to it with a hand vacuum pump or your mouth and a rubber hose. Apply suction and if you hear a “hiss”, the valve is no good. Holley made many spring rates of power valves which serve as enrichment mechanisms at part throttle. It may be that your spring is too strong and adding gas earlier in the part-throttle than it should. One experiment to run is a power valve with a weaker spring so that the extra gas only gets added when vacuum falls a lot lower in part-throttle operation.

Next up, the vacuum secondary system could be a culprit too. If the secondaries are cutting in too soon, you’re dumping in fuel that will blacken your plugs. Try a stiffer secondary spring to lean out that part of the mixture.

If your plugs are black, get a selection of leaner jets and test those 1 pair at a time so you know if you’re making progress or not.

Whatever order you might like to run these experiments in, I suggest you do one change at a time or you’ll chase your tail not knowing which change had a desirable or undesirable effect. You might also want to pick up a printed book on Holley Carb Tuning. The technology hasn’t changed in decades and there were good books on this back in the ‘80’s.

Carb tuning is in part a patience game. Test, learn, tune and enjoy.

Hope this helps.
Chris

 

Not enough info. I'm not sure what your cam specs are but from another Howards cam I saw with 560/565 lift it was ground at 109 LSA. This will make the idle a bit choppy even with the light duration. You said your timing is at 14. Is that at idle, if so your probably going to need to add some. To get it to idle your throttle is probably a bit more open than it should be and your pulling fuel from the T slots. Adding trimming at idle will allow you to back off and close up the T slots. Don't worry about your power valve unless it's leaking, it's does nothing at idle. Start with your timing curve then your idle adjustment.

 

It is possible that the engine is not producing enough vacuum at idle speed to Close the power valve at idle. You may want to consult the tuning instructions supplied by Holly. They are available on line if the paper instructions that were included with the carburetor are missing.

 

Perhaps I should have included the word "probably". I've never had any luck running 14* initial with any HEI distributor.

 

This good read from Holley.
https://www.holley.com/blog/post/how...ey_carburetor/

 

Hey OP!
We more info to help you
Carburetor model
Are you using a vacuum advance? Is it connected to port or manifold vacuum?

 

Agreed, I’ve never understood why guys don’t post more info. Do you go to the doctor and just say “I don’t feel good”? No, you tell them what’s wrong. Again I just don’t understand.

 

I'll chock that up to enthusiasts who may not know the basics of requesting help. If we were face to face they would the voice the concern and then we would ask the relevant questions. ie; year, make, model, engine size, modifications, parts replaced, attempted repairs, when dose the problem occur etc. Posting an issue is a one sided affair. "My car doesn't start, what do you think is wrong?"
All in a day.