Holley Blue's

Slow speed's ('round town) seem's to foul plug's as of late. They stay clean w/ highway speed's. A new power valve, needle and seat, reajusted both idle circut's. Still, having fouling of the plug's. Some Holley pro's imput would be much-o helpful. Would a older (point's ign.) weak spark contribute to this fouling? Thank-you for any help.

 

what size holley, whats it on ,and is your points ign. functioning properly?

 

600 vac. sec., 350 cu. Yes, it's fire's off cold and idle's fine. It's after extended slow cruise/speed's it foul's the plug's black sooty.

 

is yer secondary diaphram holding them shut, ive had a simular prob. with vac. spring/diaphrams, also is rear metering block tight? i have seen them run rich when that gasket fails/ or plate comes loose.

 

Did you set the float levels?

 

Check this out.

look down into the carb from above. just along the inside of the choke horn, there will be a series of holes there. Those are the air bleeds.

Clean those out. be gentle, use a thin peice of wire.

if the top of the air bleed gets dirty, it will pull more fuel than neccecary through the various idle circuts. sounds to me like Yours are getting there, as You are fouling in what would be a "transition" period.

check the cap, rotor and points, too. if the spark is starting to get weak, it will develop similar issues.

 

have you ever rejetted the carb?? they come from holley jetted for sea level. we always rejet them 2 to 3 numbers leaner for our location.

 

Im with a few others,check your needle and seats for debris,and check the float levels again. You may have a slight overflow problem which will spill over into the carb on the light driving but wouldnt notice it under a decent load. The air bleeds being clogged or shut is another good point. The pump itself I wouldnt think is causing your issues as its a low pressure pump that doesnt even require a regulator. A standard points distributor isnt the best anymore so i suggest an upgrade on it at some point.

 

I also had plug fouling on my 12:1 caddy with points dist. until i installed a Jacob's Ignition system similar to MSD now I run the coldest plug available with no fouling.

 

All of the above and one other thing, maybe somebody got a bit 'trick' with the secondary throttle linkage and have added a screw to pull open the secondaries instead of the vacuum, like a double pumper. Sometimes the screw location is a bit too aggressive and the secondaries will open enough to start 'pulling' fuel. It don't 'pull' fuel, but that is another subject. Good luck, oj

 

Thank-you so far. Yes I've re-set the float level to just under the hole. Lux, I have to try that tip. The gaset's are good to the metering plate. All fastener's are tighten down. The Pentronix II upgrade (coil too) is just around the bend. slammed1, I have replaced the needle and seat last month. It was worn down around the O-ring something fierce.

 

if it was a good runner that randomly started fouling, I am betting it is where the problem is. the idea of the secondaries staying a touch open is a good one, except it wouldn't idle por kaka. same with power valve.

another obvious thing to look at is the air filter. if it is dirty, the amount of vaccum "over" the throttle blades increases, having much the same effect as a dirty or clogged air bleed.

air bleeds are a simple theory that is often misunderstood. I will give it my best shot at explaining them if You would like.

 

I have also had a few bad experiences with brand new needle and seats.........cheap brands anyway.

 

Yeah, but with an electric pump, it would foul at Idle. heck, Your average mechanical pump can blow a dirty needle and seat open.

I'm still leaning towards an air bleed problem.

 

Yes indeed the air bleeds need checked and blew out at least if they havent been done.
Generally I found that if you try adjusting your mixture screws and dont get valid changes in the rpms like you should,the air bleeds are usually the culprit too.

Its tough to diagnose driveability problems over the internet.

 

One more thing make sure the idle mixture is not too rich...there's usually a range where it will idle good and not stumble, and you want it at the leanest setting where it will run right, not the richest.

 

Stock motor ? Tell us all the parts and timing and idle speed .

 

Yup. as the saying goes, "A Lean car is a Mean car".

I have just realized that the title has nothing to do with Holley Blue fuel pumps.

What pump and (if any) Regulator are You using?

 

Another thing to check, easy to do. Take off the air cleaner so you can see down in there right away. Run the motor a minute, then shut it off. If the float valves are sticking or set too high there will be gas dribbling down the throat of the carb for a bit after it's shut down.

 

Back from a cold. Update: Checking the rear float, was high. After no response, pulled bowl and bingo ther rear needle/seat oring was coming undone. Replaced it. My idle screw's are 1/2 turn from all the way shut. It's a stock 350 w/ a 268 Comp cam. Mech. fuel pump, no regulator. No vac. leak's. May pull ft. bowl off and blow out idle circut's. Thank's again to all who chip in to solve this problem-Nick.