power dies at mid-range... please help!

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thejohnnyguy

thejohnnyguy

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From a stand-still if I stomp the gas the car wants to get up and go, tires start spinning and such, but only for a short while before what seems like it just gives up. any time between 1500 - 2200 rpm range it's great, but after that it's a grandma car... :p I'm wondering if it could be off timing and the vacuum advance is causing it to advance too much? I havent been able to get it up to reasonably high RPM's either... (may be due to 2.97 gearing...) but I think it should have much more power that i'm gettin out of it... Suggestions anyone? it's a beefy 318 (possibly stroked im not sure) with 340 X heads and 340 intake, running to a 904 (which was rebuilt with a shift improver kit(not by a professional, but by high school kids)) to 8 3/4 SG rear with 2.97 gears
 
what carb is on it????? could be running out of fuel my car was doing it about mid track last yr. and went to check things over and carb was running out of fuel.....i had a dp on it though....mike
 
earthmover said:
what carb is on it????? could be running out of fuel my car was doing it about mid track last yr. and went to check things over and carb was running out of fuel.....i had a dp on it though....mike
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Edelbrock 600cfm, I cut fuel pressure back to 5.5lbs because prior to that the carb was flowing gas into the intake after shut-off (even when cold) from too much pressure... is 5.5 lbs not enough maybe?
 
i use to run 7/8 psi on my duster im not to up to speed on the eld. carbs...but you could try and turn it up just a little at a time a see. what reg. and pump you running also does the gauge have the fluid init??? if so you may want to drill a samll hole in the back a drain that out it can cause problems sometime not saying thats it but it can....also may want to do a fill check if your running a elec. pump.. by fill test you take the line loose from carb and time how long it takes to fill 1 gal. and check the specs on your fuel pump to see if they are inline...i test mine without the reg. and then with the reg....hope that helps maybe some of the others will have more ideas but that what i ran in to with my car..mike
 
earthmover said:
i use to run 7/8 psi on my duster im not to up to speed on the eld. carbs...but you could try and turn it up just a little at a time a see. what reg. and pump you running also does the gauge have the fluid init??? if so you may want to drill a samll hole in the back a drain that out it can cause problems sometime not saying thats it but it can....also may want to do a fill check if your running a elec. pump.. by fill test you take the line loose from carb and time how long it takes to fill 1 gal. and check the specs on your fuel pump to see if they are inline...i test mine without the reg. and then with the reg....hope that helps maybe some of the others will have more ideas but that what i ran in to with my car..mike
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Mechanical fuel pump from advance auto (maybe AC Delco?) to a Mr.Gasket fuel pressure regulator with a dial that goes from 1 - 6 lbs. I may have to get a new FP reg to try upping the pressure
 
Longgone said:
Sounds like fuel starvation......is the pickup screen in the tank clean?
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all clean and new, perhaps i'll get a higher fuel pressure reg since mine only goes to 5.5lbs... i'll shoot for 7 -8 ish...


and no, no backfire
 
Are the secondaries opening fully? Are the primaries too?

How new is the fuel filter?
 
I'll check the throttle cable to make sure it's reaching WOT. carb was just rebuilt too... new fuel filter.. :p I have to also check the kickdown linkage and make sure it's pushing the arm all the way back.
 
in my experience you can hear and feel fuel starvation, kinda poofing sound with loss of power.

slight timing issue will sound fine but not have the power you want.

just sharing....maybe helpful... maybe not generalizable
 
You shouldn't run that carb with over 6.5 PSI. At 5.5 PSI you shouldn't be getting fuel starvation, at least not from the fuel pressure side of the equation.
With those 2.94 gears, and depending on your cam specs, it may be just waiting for the rpm to climb into the operating range of the cam / intake manifold before it can breath and pull properly again. Have you tried holding it in one gear to see if it will eventually get up and go, say around the 3000 - 3500 RPM area?
 
OldVart said:
You shouldn't run that carb with over 6.5 PSI. At 5.5 PSI you shouldn't be getting fuel starvation, at least not from the fuel pressure side of the equation.
With those 2.94 gears, and depending on your cam specs, it may be just waiting for the rpm to climb into the operating range of the cam / intake manifold before it can breath and pull properly again. Have you tried holding it in one gear to see if it will eventually get up and go, say around the 3000 - 3500 RPM area?
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Ok, so I think it was a combo of having 2.94 gears (which I would love to now get rid of, haha) and my secondaries weren't opening. It seems like I had to adjust the electric choke a good bit to get to where it would allow the secondaries to open... is this normal?
 
Well, if the choke is hugely out of adjustment, or the electric springy thingy is messed up, yeah, it could be normal..... Did your idle drop big time once the choke was spun?
 
Cool I called one right for once! Lol...I dont under stand the choke thing.It must have really been adjusted tight and not opening? Are you sure the choke opens on it's own? Electric chokes are super easy to adjust,just turn it until it just closes.Done. It should open fully from there.

Did you make sure the kickdown is adjusted right as well? If not it will destroy the tranny quickly..
 
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