Power Dies on WOT in lower rev range

[Brendanchambers]

69 RR, 383, starts and idles fine, drives fine until you give it all its got, especially in the lower rev range.....i'm not currently running additives, maybe i should add this....(just running 93 octane - 98ron in aus)

do you think it just needs a tune up? or?

it hasn't been running since july 2020.....its finally being registered in Australia now and i guess it probably needs a decent run in however i'd prefer to know everything is working correctly.

what do you all think, try additives and go from there? or send it somewhere for a tune up.

 

[Don Frelier]

Check your accelerator pump.

 

[Brendanchambers]

Check your accelerator pump.

How would you be able to tell if its operating okay or not ok? any ideas?

 

[Don Frelier]

Remove the air cleaner.
Look above the carbeurator near the front and manually twist the throttle arm a good full shot.
You should see two strong streams of fuel throughout the rotation of the throttle.
If it's weak (dribbles) or starts 1/3 - 1/2 way through the rotation then it needs a new pump or seal or perhaps a good cleaning.
Don't do this repeatedly you'll put too much fuel in and flood it.

 

[Brendanchambers]

Remove the air cleaner.
Look above the carbeurator near the front and manually twist the throttle arm a good full shot.
You should see two strong streams of fuel throughout the rotation of the throttle.
If it's weak (dribbles) or starts 1/3 - 1/2 way through the rotation then it needs a new pump or seal or perhaps a good cleaning.
Don't do this repeatedly you'll put too much fuel in and flood it.

thanks i will have a look

 

[Ron H]

Another check is the fuel filter that might have some clogging from sitting or some carbs have a filter screen that can be checked...if some clogging is the issue.

 

[Ranger16]

what do you all think, try additives and go from there?

NO! Leave the snake oil on the shelf.

 

[RJRENTON]

I agree with #4 & #7....
Also consider looking at the carb's step up pistons, which controls the primary metering rods. If the step up pistons are stuck in the down position, the carb will run lean at WOT. Also consider a tired fuel pump, that cannot supply the VOLUME needed at maximum load, causing a lean condition. Consider also, stuck advance weights in the distributor. This would cause a very sluggish acceleration profile.
The Carter AVS carb has s fuel inlet screen located in the carb body, accessible by removing the fuel inlet fitting nut, after disconnecting the fuel line. Just a few more points to ponder.
BOB RENTON

 

[Ron H]

I agree with #4 & #7....
Also consider looking at the carb's step up pistons, which controls the primary metering rods. If the step up pistons are stuck in the down position, the carb will run lean at WOT. Also consider a tired fuel pump, that cannot supply the VOLUME needed at maximum load, causing a lean condition. Consider also, stuck advance weights in the distributor. This would cause a very sluggish acceleration profile.
The Carter AVS carb has s fuel inlet screen located in the carb body, accessible by removing the fuel inlet fitting nut, after disconnecting the fuel line. Just a few more points to ponder.
BOB RENTON

ok lol, then checking the carb inlet (if so equipped) as mentioned in post #6 wasn't agreeable...just my pin of course BR.

 

[Brendanchambers]

thanks for all your help....will have a look at this after work and see how i go.....
i'm very very new to the old carby tech so hopefully i dont screw something up...

 

[hunt2elk]

If the carb checks out ok and you get to the fuel pump, check the length of the pushrod. There have been a lot of complaints of all the new ones wearing down quickly.

 

[wagonman]

If the carb checks out ok and you get to the fuel pump, check the length of the pushrod. There have been a lot of complaints of all the new ones wearing down quickly.

Had that on the 68 r/r new cam rod and pump. Was worried about the cam but OK with the Comp hardened tip rod.

 

[furious70]

Bad/old gas if it's been sitting?
Does it cut out, bog, or just feel lazy?

 

[Brendanchambers]

Bad/old gas if it's been sitting?
Does it cut out, bog, or just feel lazy?

filled the tank up this week and drove about 30km and it was bone dry so shouldnt be old gas, it just bogs....

 

[Brendanchambers]

i've literally never revved it out as i'm taking it pretty easy, so i cant comment on lazy power however its no rocket compared to my 6.4L hemi 300 SRT

 

[furious70]

spoiler alert - it's going to feel like a dog compared to a 392 car even when running correctly.
So it's never run 'right' since you've owned it? Back to basics, timing, tune up and go from there. Maybe you'll find a bad plug or wire.

 

[Brendanchambers]

haha, guessed as much....

nah i did run through the rev range in 3rd and it felt like it will actually pull quite well so i'm not worried, i've only got to about 4k , on that, how hard should you rev these engines.....presumably stock....6k? or

 

[Don Frelier]

If it's stock I would say 5,500 max. It won't be pulling hard after 5,000 anyway.

 

[Brendanchambers]

i will be able to take it for my first decent drive tonight......up until today i've only driven it on a permit (uninsured and unregistered)....so i was taking it extremely careful

 

[Don Frelier]

uninsured and unregistered

Uninsured is not a smart thing to do my friend at least here in the States.