1968 Roadrunner needs something ????

[383MovingViolation]

My '68 Roadrunner has a 440HP engine (I believe around 375hp) that's running a little sour. It starts fine, idles fine, revs great from with good throttle response. But here's the problem, when I take off and hit the gas peddle down hard, it wants to bog and sputter before it takes off. It will do this every time and the engine is warmed up. It is an automatic, 750 Edlebrock carb and 3:73 rear gears. I had a good mechanic check timing, plugs, and he adjusted the carb. Also changed metering rods. It ran good for awhile but now it's doing the same thing again. I also run 93 octane fuel. 275/60-15 on the rear that I can break loose. That's shameful. Anyone have any ideas as to what might need adjusted or replaced. It's a Roadrunner with a 440HP engine and this thing should jump out and go. Thanks for any advise.

 

[1967coronet440]

What intake and cam are you running?

 

[droptop]

Bog is a lean condition. Check your accelerator pump and run as much initial timing as you can without making it ping.

 

[oldbee]

How old is carb? Rebuild needed?

 

[hashmaker]

Is your carb and AFB or an AVS? The AVS are more easily tuned with the screw adjustment. Look at a Summit catalogue and read the description. The AFB stages rich too soon and gas movement lags. Hence the lean out condition. The springs on the metering rods and the size of the rods has everything to do with a smooth transition from 2 bbl to 4bbl opening.

 

[67 coronet]

1st thing i would check would be the squirt out of the accelerator pump.look into the carb air horn while you move the throttle.does it squirt right away or slowly?should be instant squirt.

 

[383MovingViolation]

The accelerator pump function looks good. I was wondering if I need a carb with vacuum secondarys ? My car is an automatic and I read that mechanical secondary does not work so well with automatic ??? . The carb is fairly new but the metering rods were changed because my mechanic seemed to believe it was to lean. I'm not sure about what cam the engine has, I bought the car with this set-up. What carb and cam are you guys using? I believe it is a fuel problem but I just don't know where to start. I hate to just start throwing parts at it and hoping for the best but this engine should really launch this car. Thanks for any help

 

[Ranger16]

I have the same carb on my 383 with no such problems.
Maybe this will be of some help.
http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

 

[Billccm]

Like ranger I too have the same set up; 383 auto.

I used a vacuum gauge to set up at idle. Best I could get was 11.5 inches. It runs great, but slightly rich. Once I address other issues I might play around with jets.

 

[oldbee]

What are your timing specs also?

 

[oldbee]

You kinda have a vacuum secondary already a true double pumper/mechanical secondary would have another acc.pump on the rear side like a Holley. Probably just need some more tweaking on current setup.

 

[Richard Cranium]

I had an issue with my carb & it turned out to be the metering rod springs. The engine would surge at a steady speed & under a light load. The tuner said that vacuum was making the metering rods flutter & the next heavier spring solved my problem.

 

[67 coronet]

your carb is a 750 cfm,if you didnt know.might be a good idea to take the top off and see if there is a bunch of dirt in it.they pull apart pretty easy and does no gasket damage.try spraying it clean and retry it.could need a rebuild kit.lots of small pasages can get plugged if carb sat for a while.