Ok, I took my car out for a blast today. I noticed it breaks up under WOT (3500 rpms or so) Holding back isn't pulling like it should.
it has a mild cam / edlebrock intake and carb / MSD Ignition...
I pulled the plugs and they were all black and burnt like it was running rich.
I changed out all the plugs and still no change. Anyone have any suggestion?

thanks

were the plugs pulled right after you ran it on the side of the road?

or after you got home.idled etc....?

the reason i'm asking is reading plugs will only be accurate if you run the car,shut it down. coast to the side of the road etc....

put a timing light on it. what is your total timing and when is it all in...

What model # carb? Is the carb dead stock with orig jets and rods?
Sounds as if it is stuttering (lean) in the power curve.

Black plugs could be a rich idle cond.

i changed the plugs after i noticed the car bogging down. I have a Edlebrock carb 1406 electric choke. It's more so taken off in first, (breaks up then seems to clear after a certain point)....
then on the highway... cruising at 60, its ok... as soon as i punch it, it starts bogging.... More or less if a drive ir normally its unnoticed.

thanks
paul.

Oh yeah i believe my timming is set @ 6 degrees BTDC on the timming.
i have to double check today with a timming light. What is the best way to time it?

Probably something very basic. Set timing at 8 to 10 degrees at idle, make sure vacuum advance is disconnected. Slowly rev engine up (using your hand on carb throttle) to about 3,000 rpm and you should see timing advance quite a bit. If you have a degreed balancer, you should see max timing of about 34 to 36 degrees, all in by about 3,000 rpm. If timing not advancing, check dizzy, looking especially at weights under rotor. After you confirm it's working, re-connect vacuum advance (assuming u had one to begin with).

Also, I would replace the fuel filter and look carefully at your fuel lines. There are typically some rubber pieces and they get brittle and crack. Once that happens, the fuel pump will suck air instead of fuel, producing a lean condition with symptoms as you describe.

Check all other basic tune-up items too, like PCV, cap, wires, etc. Look carefully for any vacuum leaks.

-

Paul, I have some bad news for you just as it was given to me. The Edelbrock 1406 carb is jetted for fuel economy, not performance, especially on a big block. The 1405 may be better, but the 1406 is only rated for small blocks and economy. I learned that the hard way. I bought one thinking it was just the electric choke version of the 1405(performance carb), but it's not. Mine did the same thing. At top end it had no power AT ALL. I have since switched to the Thunder Series 650 and it's like a night and day difference. I tried to rejet the 1406 with their calibration kit, but I could only get so much out of it since it just wasn't made for performance. I thought that if you just jetted the carb to the same settings as the 1405 it would run like a 1405, but come to find out the internal construction is different.

Here is the description Edelbrock has on their website for the 1406:

1406: Electric Choke
CALIBRATED FOR FUEL ECONOMY
Designed for small-block and small displacement big-block engines, these carbs are recommended only for stock to Performer level applications. They are not recommended for use on RPM or Torker II intake manifolds. Match with an Edelbrock Performer or Performer EPS manifold and other brands of similar design. Calibrated 2% leaner than #1405. Includes both timed and full vacuum ports for ignition advance.

That same carb was on my '68 396 when I bought it. It was old and tired, so I attributed my problems to that, but it did the same thing you're describing. I knew it was old and tired, and I prefer Holley's anyway, so I swapped it for a Street Avenger 770, upgraded to a Performer intake and put some new plugs in it (and did nothing else... no messing with timing or destributor). Now that thing absolutely screams with no signs breaking up. Not sure if this helps you... but that's been my experience, anyway.

~Bob

thanks guys, i messed up.... I have a 1407 Edlebrock 750. I dont know if this makes a difference. If its not the carb, could it be the MSD Setup?

thanks guys, i messed up.... I have a 1407 Edlebrock 750. I dont know if this makes a difference. If its not the carb, could it be the MSD Setup?

as mentioned before.

check total timing......you want to be around 36 total around 2500 rpm or so...

timing at idle 8 or so

with a mild perf cam then around 12-17 or so...

and 36 total!!!!!!!!!

then go to carburation...........

Faulty rev limiter?

faulty Rev limiter...On the MSD? I checked it, it has a 6000 RPM limiter.
How do i determine if its faulty?


thanks
paul

Pull the rev limiter out of the box. I am assuming you can put different rpm chips in your box. With the chip removed go drive your car and see if it changes.