Help, I am ready to give up!

I have a 1969 Camaro I just built a BBC 468, I am struggling with a new carb, and its about to get the best of me. The motor is a 454 with forged flat-top pistons, and closed chamber 69 heads, 10.0/1 compression with a solid flat tappet cam, I have a 4150hp 600 holley on an edelbrock rpm air gap intake. According to my math I should be under carbed, but I am fighting a hopelessly over rich problem that has me at my ropes end! Anybody have any suggestions I would greatly appreciate it, Thanks Kelly:CRY:

Just how "hopelessly overrich" are we talking here? Clouds of black smoke, or just really lousy gas mileage? Jetting too fat, or float not sealing?

fouling plugs, and clouds of black smoke, I have blocked off the secondary power valve, and almost bottomed the mixture screws to the lean side, and it has had no effect at all. I am really lost on this one, but hoping somebody can give me some ideas, thanks, K

What is the fuel pressure at the carb inlet?

A Little Over 10 Psi, It Bounces Between 10-15 Psi Eratically, Thats On My Line Guage At The Carb

i ALSO HAVE THE CARB JETTED DOWN TO FACTORY SPECS, F-70, R-70, WITH A 6.5 POWER VALVE IN THE PRIMARY METERING BLOCK AND A PLUG IN THE SECONDARY BLOCK. tHE FACTORY SPECS ON THIS CARB LIST NO P. VALVE IN THE SECONDARY BLOCK, DOES ANYBODY KNOW IF THE 600 HP HOLLEY CAME WITH A POWER VALVE IN THE SECONDARY BLOCK?

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Originally Posted by colesscamaro

A Little Over 10 Psi, It Bounces Between 10-15 Psi Eratically, Thats On My Line Guage At The Carb

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If you'll adjust that down to 5 lbs, your problems will go away.

tHE MOTOR HAS BEEN DOWN FOR A COUPLE OF YEARS, I JUST RECENTLY PUT NEW CYLINDER HEADS ON IT AND GOT IT BACK IN THE CAR, IT ONLY HAD 1000 MILES ON IT WHEN I HAD A PROBLEM WITH ONE OF THE HEADS. THE BOTTOM END WAS STORED ASSEMBLED, AND I MADE SURE TO LUBE THE CAM BEFORE WE REFIRED IT JUST A COUPLE OF WEEKS AGO. I HAVE HEARD THE STORIES OF HOW SUCCEPTIBLE BBC'S ARE TO WIPING OUT CAMS, AND I ALMOST WONDER IF THE CAM WENT FLAT ON ME, I AM REALLY HOPING THIS IS NOT THE CASE!

Forgive My Ignorance But How Would I Do That? I Am Running A High Volume Holley Mechanical Fuel Pump, Would My Only Option Be To Add An Inline Press. Reg. ?

Scroll down to page 118 here and see the 4304M fuel log. Mount it on the Holley and run a return line to the tank. Pressure adjusts right on the log.
http://www.malloryperformance.com/pd...m_Products.pdf

tHANKS FOR THE TIP! IF IT WORKS YOUR A LIFESAVER, I APPRECIATE YOUR HELP, K

Agree fuel pressure is too high... you want somewhere between 6-8psi max. Which holley pump are you running? Electric or mechanical? You'll want a pressure regulator... that said, I've had my holley run with over 11psi at times without overpowering the seats and going over rich.

Another possibility is a blown out power valve... they will dump gas like crazy

Agree you are under carbed so your motor can't breath over about 4500-5000rpm... you should have at least 750cfm for street application and probably 950cfm minimum for a race car.

-Chris

definitely check the power valve, and install the pressure regulator with return line. I have heard of some people using the vapor canister return line as a fuel return.

if the line pressure were too high and was in turn overpowering the seats wouldnt that be eveident when trying to set the float level? I have set the float level with the engine running and had no signs the seats were letting fuel by, ie, fuel coming out of the sight hole. I have never had trouble with pressure before, with a different holley carb, I just cant seem to get the thing to lean out it loads up at idle ferociously almost as soon as the engine is running

most likely blown power valve... sounds like needle is sealing despite your high pressure although this could turn into an intermittent problem when moving a lot of fuel and having the needle stick open... it can happen... best to run about 7 psi... replace your power valve and see if it gets any better.

BTW: very nice looking Camaro!

-Chris

fuel 5-8 lbs should be fixed

Put a stock pump on and try it.

power valve was the first thing i replaced, even tried running a plug in the secondary metering block, it had no effect whatsoever

Keep us posted on what the problem was, thanks Kurt

R Pope has given you the cheapest, easiest and quickest fix.
"Put a stock pump on and try it."

Even cheaper---just disconnect the line to the carb and plug---if it clears up you have found the problem--

I have used this numerous times to prove that domeone had too much fuel pressure

if your runing that big cam 588/588. 274 @050 and 107 lca that 6.5 PV is to big should be a 2.5 or a plug if a plug jump up about 10 jet sizes up and the carb is small for your engine so i would bet with that cam you have your idle turn up past you idle circuit so you will have to crack the back barrels so you can get the idle circuit to work

The motor is producing 10-12in. of manifold vacum at idle, I tried a 4.5 power valve without any change at all. I have the factory specs on the carb, and they show no pwt valve in the secondary block w/ 70 jets front and rear. It did clean up the mid range throttle response when I eliminated the secondary pwr valve. I am still having no success getting the motor to idle without severely loading up. I am trying to locate another carb to compare results, and eliminate the possibilty of an ignition problem, The msd components have all checked out ok, but I am not ruling anything out.

try another carb

Did you get the fuel pressure adjusted???? That small of a carb, maybe some bleed holes in the throttle blades????? Think the fuel pressure has to be correct before the carb will work right.....

a few questions

Exactly what number holley carb do you have?
Is it new or has it been rebuilt or altered?
are you running an aircleaner?

What is you timing set at and is you timing marks/cam/tdc all checked and proven????

Does your throttle blades have holes drilled in them?

How far open are the throttle blades front and secondary???

Why are you trying to run so much fuel pressure?

What type float bowls and floats are on your carb???

pull the front float bowl and jet plate put a straight edge on carb body from from screw hole to screw hole in an x pattern many times people over tighten the float bowl screws this causes the carb body to bend, and the gasket to not clamp in the center where the power valve is causing an internal vacuum leak it takes vacuum to overcome the spring in the power valve. if this is the case cut a peice of heavy glass about 1 1/2 in x 8in long wrap some fine wet and dry sand paper around it with solvent or wd 40 surface the carb body until you have full contact I keep apeice of glass in my tool box and do this to every holly carb i work on you will be amased at how many you find with that problem it saves alot of problems then dont overtighten the screws. also check the jet plate and make sure the vacuum passage to the power valve well is not blocked some times sombody used the wrong gasket blocking the vacuum holes holly carbs are very simple contraptions its amasing the work as good as thy do there is no magic here its not rocket science dont let it intimidate you well thats my 3 cents worth ......ted

I like that i didnt even have to read 1/3 of the page before I saw it has already been answered. Fuel Pressure Fuel Pressure Fuel Pressure. Edelbrock carbs take a MAX of 6.5PSI. I run mine at 7psi and end up with a rich idle with everything leaned out all the way.. if your running 10 on anything thats just.. wow.

Call Holley or look in the instructions for your carb and find out what they say to run for max pressure and run THAT. NOT HIGHER OR LOWER. DO NOT BE LIKE ME AND RUN .5 PSI HIGHER. BAD IDEA. IM TOO COOL FOR RULES, YOUR NOT.

HOLLEYs will take abit more fuel psi then the old afb or edelbrock they do not like hi fuel psi they will FLOOD

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Originally Posted by jerry clayton

a few questions

Exactly what number holley carb do you have?
Is it new or has it been rebuilt or altered?
are you running an aircleaner?

What is you timing set at and is you timing marks/cam/tdc all checked and proven????

Does your throttle blades have holes drilled in them?

How far open are the throttle blades front and secondary???

Why are you trying to run so much fuel pressure?

What type float bowls and floats are on your carb???

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list#0-80540-1 Model#4150hp, I bought the carb with a broken baseplate on e-bay, I have been thru the carb, replaced the baseplate with the factory part# baseplate, and all new parts throughout. I am running a 14"x4" K&N filter, initial timing is set at 12 degrees with total timing at 32 degrees I am running a fluidamper, and have personally degreed the camshaft myself. The throttle blades are all four drilled and the curb idle set primary, and secondary together, I am just running the pump pressure from a holley high volume mechanical fuel pump, which has never before been a problem with other holley carbs. I will get a regulator to get the pressure down, but have not as of yet.

OK So heres my status, I have repiaced plugs, wires, cap, and rotor, the motor runs strong, pulls like a frieght train, then after any time spent at city speeds, or just cruising below 3,000 rpm, it starts to develop what I can only describe as a sparatic miss. When I jump on it at low rpm it starts to pull hard thru 2nd,(4spd) bottom of 3rd is a little flat, and as the rpm gets to about 4,000 it starts "shootin ducks" and noses over into 4th gear. After a cool down period, it will run strong, crisp throttle response, and then repeat the same behavior again. I'm stumped! Oh yeah, I put in an in-line regulator and got the fuel pressure down to 5psi @ idle, I only have a guage in line at the carb, so I cant see what it is doing at speed:confused:

look at the coil or ignition box ? if you have one also sounds like the fuel is getting hot ?if yor running a hei ignition check for 12 volts .were is your plug gap at

I made some sweeping changes to the motor, the MSD turned out to be down on power due to a faulty ground connection, as well as the + connection was made with insuffecient wire size for the distance to the battery(battery is in the trunk) new plug wires, an adjustment to retard the timing for total timing of 34 degrees. The fuel pressure turned out to be a non issue due to a faulty gauge, installed new plugs, Most significantly, was a carb change from the holley 600hp, to an Edelbrock performer 750cfm vaccum secondaries, manual choke. All those changes only improved the rich mixture problem, but did little or nothing to improve the driveability, surging, and popping at high rpm were still relatively unaffected. That was until I replaced the cap and rotor on the distributor. After careful examination, the rotor button in the cap showed signs of pitting, but even under a bright light and magnifying glass, there were no obvious signs of trouble. But once the new cap and rotor was installed, and one final check of the timing, and carb adjustments, in 4 consecutive full throttle, no mercy passes and a tank of fuel around town, the problem is gone without a trace. My bargain ebay Holley, didnt turn out to be such a sweet deal after=all. Thanks all for your advice and ideas to get me headed in the right direction, HOTROD.COM ROCKS!!!!!!!!!!!!

I have a 468 also with a 1050 dominator fuel pressure 5 lbs with engine
running...never a problem// r dobbs