Runs good at idle but it runs like crap at WOT

[TheSwede]

Hi, I have a Holley 850 dp on my 383 as a tryout and it was running great until yesterday, car runs good at idle and part throttle but when I press the pedel more than 50 % it is loosing all power and runs on 5 cylinders, releasing the pedal and in runs good again.
This problem came over night and the battery was disconnected, fuellines are new and filter too. Plugs wires etc are all new.

The only thing I have done is that I mounted a smaller air filter and got a carb poff, otherwise it is all as yesterday.
Could a blown power valve cause this?
I will try it with the old larger air filter to see if it helps.

Suggestions?
Carb?
Coil?
Distributor?

Car runs good revving in neutral, responding is nice, it is only in drive it will running like crap.

 

[62MAX]

Hi, I have a Holley 850 dp on my 383 as a tryout and it was running great until yesterday, car runs good at idle and part throttle but when I press the pedel more than 50 % it is loosing all power and runs on 5 cylinders, releasing the pedal and in runs good again.
This problem came over night and the battery was disconnected, fuellines are new and filter too. Plugs wires etc are all new.

The only thing I have done is that I mounted a smaller air filter and got a carb poff, otherwise it is all as yesterday.
Could a blown power valve cause this?
I will try it with the old larger air filter to see if it helps.

Suggestions?
Carb?
Coil?
Distributor?

Car runs good revving in neutral, responding is nice, it is only in drive it will running like crap.

This is something you and most others need to read from Holley Tech literature before jumping to conclusions about power valve !!

 

[daredevil]

How did it run before the little filter. It may be too restrictive. Also check all rubber fuel line hose for kinks cutting off fuel delivery. Next I would check float level. Too low and engine starves at higher rpm.

 

[67 coronet]

how is the timming advance?make sure it is not sticking.

 

[Garys1969RR]

Sounds like an over rich condition due to the restrictive air filter. These motors need LARGE free flowing air filters to perform well. Only other problem ( if it persists after installing a larger filter) is a lean condition in the secondary of the carb. What is a carb poff?

 

[Michael789]

Has anyone stop to think that this might be too much carb for a stock 383? Sounds like a lot of carb if that's the case.Is the motor stock? Just asking ,you didn't specify if the motor had been built for street racing etc. Good luck .

 

[66Satellite_in_NC]

It's not uncommon for a car to free rev great but die when a load is placed on it. Good luck on finding the problem quickly.

 

[bandit]

"battery was disconnected..." Make sure battery cables are tight and the ground to the engine is good. Is your ammeter gauge showing a good charge?

 

[TheSwede]

Thanks for all the input, I have solved the problem, it was the hose from the crank case vent that was in contact with the acc pump making it stuck, an easy problem once you start looking...:head_smack:

BTW, the car runs great now, getting better and better, laying the neighbourhood in smoke in no time. Revs nice too, will post a video if the weather stay good!

The 850 is a little big but it make a lot more power than the Eddy 750.
Had a shot on new Holly 750 dp on ebay but seller won´t ship...

 

[Meep-Meep]

First, I'd get that 850 DP off that 383. But if it was driving OK before and now suddenly you have issues, then check the float levels and fuel pressure. Also a restricted fuel filter will cause you lots of grief.