1971 rocket 350 tuning problem, stumped !
 

I have a 1971 cutlass supreme Convert that My Father bought NEW. engine was "completely rebuilt" in about 1999. 350 4 barrel completely stock ,(Inc Stock Cam). Changes, "true dual exhaust", and added an "HEI Dist". Problem...Starts right up and "runs"(,but idles Very Rich). but almost immediately "fowles" the plugs ( DRY/BLACK). Already "Checked", Compression in all 8 cylinders 160 PSI, NEW plug wires, Coil in cap, (13 volts going to the coil in the HEI CAP. I've installed a NEW Edelbrock Carb. FUEL PRESSURE 6 PSI. Vacuum at "idle" is 16 inches. Timing. 12-14 BTC.* ( "True TDC", was checked with a "Piston Stop")*. Has 160 PSI in Every Cylinder. I've tried 2 different sets of spark plugs set at .045" (Delco 45 & Autolite 86), Both BRANDS get Fowled Almost Immediately ! Carb is Not flooding, I've tried both the Orig Q-Jet and a new Edelbrock carb. timing is correct, compression is like new, ****WHAT CAN I POSSIBLY BE "MISSING****??? Thank you for your help, running out of Ideas ! :-(

I would think that with a stock cam you have more then 16” at hot idle.

I would venture a guess that your vacuum is low due to a worn timing chain.

take all your plugs out.
remove the Dizzy cap and bar the crank back and forth about 3 inches.

does the movement of the rotor lag behind the crank movement?

IT ALREADY HAS A NEW DOUBLE ROLLER CHAIN WITH ONLY ABOUT 3000 MILES ON IT. IT IS INSTALLED CORRECTLY AND NOT STRETCHED. sorry bout the caps.

Just because it’s new and installed dot to dot does not mean it’s made right, as many folks have found out once they took the added time to degree in there cam with the new parts.

did you degree in your cam even though it’s stock?

Since you have 2 carbs acting the same way your issue is either that you have a vacuum leak at a intake gasket, or the cam timing thing I posted about here.

also your balancer ring may have slipped and your not setting the timing where you think you are.

after checking for vacuum leaks I would then confirm that the TDC mark on the balancer is truly taking place when number one is at TDC.

Sorry, I missed that you checked the cam degree .
well it is possible that both carbs have a issue .

When todays fuel sits too long it turns to a mess and such a condition could be effecting both carbs I guess.
gummed up passages can take place, in fact I have seen where a simple carb cleaner spray out of collected dirt in a carbs idle air bypass passages restored normal functioning in less then 5 minutes.

with the carb you have on there now once the choke is off does turning the idle mixture screws in make the motor want to stall?

is the firing order correct?

I have worked on motors where it was wrong and the fuel was getting pumped back up out of a intake port and then into other cylinders, yet the engine was not back firing thru the carb.

In general it always pays to go back and review the last thing you did before things turned to crap.

the golden rule of working on a good running motor is to not make more then one change at a time before you confirm that all is still well.

finally got it to Idle smooth and hold 19" of vacuum, BUT... go down the road about 1/8 mile and it feels like it's running out of gas ! (But it has fresh gas into a cleaned tank, and holding 5 psi fuel pressure ! back to the house. I can let it idle and it's fine, then slightly rev it to about 2000 then back to idle. it will do fine until the 4th or 5th try, then is starts breaking up again until I let it just idle. still holding 5 psi ( premium gas with a little "Sta Bil" in it. ( Car sits a lot for long periods. I've got 1 more New Edelbrock 600 on a perfect running car, going to try it next.

It sounds then that your issue may not be fuel pressure, but volume .

if any of your rubber fuel lines in the system that jump from steel line to steel line are dry rotted or not tight enough then any type of fuel pump will find it far easier to suck air instead of heavy fuel.

you may also have a kinked off steel section of fuel line in the system that is restricting flow.

I have had rotted rubber fuel line that on the suction side of the pump would not drip fuel, but the pump was sure as hell sucking air.

your fuel pump itself could be bad if it’s over 15 years old since many of the NOS ones today that you can purchase are made with diaphragms that are not made to handle todays Alky cut fuel for very long.

fuel pump is 2 weeks old. about the only thing I have NOT Done yet is disconnecting the Fuel Line from the tank to the pump, and "blowing it out". Line has a "CLEAR FILTER"(BETWEEN the FUEL PUMP to the Carb) and it is perfectly clean. starting to think, Maybe, the "sock" in the tank may be getting plugged. The Fuel Tank has never been down since the "ASSEMBLY LINE". LOL

Besides a clogged with dirt and bad fuel condition of the sock I have seen cases where they just collapse on themselves!