Hesitation on acceleration
Thread Starter
Intermediate
Joined: Apr 2004
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From: Hixson Tn
Hesitation on acceleration
I recently reinstalled my stock intake and an Edelbrock 1901, 750cfm carburetor in my 1970 454. I set the timing to 6 degrees btdc and am using a pertronix system instead of points. I also replaced the lifters and pushrods while the intake was off. My problem now is a severe hesitation when I hit second gear after WOT in first. I'd say my power is cut in half at this time. If I back off the throttle a little and then slowly get to WOT in second, it picks up again to full power. Before I start replacing random parts I'd like to get a few opinions on the situation. Initially I'm guessing that the engine is being overwhelmed by fuel considering I pulled the carb out of the box and bolted it on without any adjustments. Then I wonder if my pertronix unit is improperly adjusted and should I go back to points? Could I have a bad coil? As you can see I'm pretty lost and am sure that somebody out there may be able to help or at least make a suggestion on where to start. Any help is appreciated.
Chad
Chad
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Re: Hesitation on acceleration (ATCGuy)
How did it run with whatever combo you had before the change? You did not say.
This almost sounds like fuel starvation on the bb with the Q-Jet. I would first pull the paper filter in the inlet and remove the "button spring" they put in there to keep gas from being syphioned backwards. Remeber a 1901 is supposedly calibrated for 350's - 454's and are kind of lean. If I remember they use 69's for the mains with 43 rods. A q-jet on a bb really needs about 74-76 main jets and likes the 43/44 rods. Don't start messing until you make sure the fuel flow is good. Another area to look at for fuel flow is what is the pump putting out. If it is the orgional one - it is probably weak. Check the flow rate into a bottle. Haynes or Chiltons manuals tell how to run a test.
Two other fuel flow areas are: kinked "S" hoses feeding the fuel pump and the fuel "sock" on the pickup in the tank being partially plugged.
As far as the distributor goes, a bb can use a little more initial timing around 10-12, but before you change - get an adjustable timing light and see what your total timing is and whether the centrifigual and vacuum advances are working ok. Total timing for a bb should be 36 degrees and all in by 3000 rpms. Check it out.
This almost sounds like fuel starvation on the bb with the Q-Jet. I would first pull the paper filter in the inlet and remove the "button spring" they put in there to keep gas from being syphioned backwards. Remeber a 1901 is supposedly calibrated for 350's - 454's and are kind of lean. If I remember they use 69's for the mains with 43 rods. A q-jet on a bb really needs about 74-76 main jets and likes the 43/44 rods. Don't start messing until you make sure the fuel flow is good. Another area to look at for fuel flow is what is the pump putting out. If it is the orgional one - it is probably weak. Check the flow rate into a bottle. Haynes or Chiltons manuals tell how to run a test.
Two other fuel flow areas are: kinked "S" hoses feeding the fuel pump and the fuel "sock" on the pickup in the tank being partially plugged.
As far as the distributor goes, a bb can use a little more initial timing around 10-12, but before you change - get an adjustable timing light and see what your total timing is and whether the centrifigual and vacuum advances are working ok. Total timing for a bb should be 36 degrees and all in by 3000 rpms. Check it out.
