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Discussion Starter · #1 ·
my holley 600 w/ electric choke is sputtering, hesitating, and finally takes off when i floor it. the back two valves on the throttle body wouldn't open when i pushed the acclerator, the little brass arm(don't know the name) that is supposed to open them doesn't seem to be working.i rigged the arm so it would open them and when it idles it revs fine. but in gear it hesitates a lot. is it getting to much air now?
 

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it could be a couple diff things... but first is it a double pumper (mec. secondarys) or vac. secondary carb? if its a vac secondary carb and you "rigged" it to open the secondarys, my guess would be that they are opening too early, even having them open when crusing witch is making it run too rich.
 

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Discussion Starter · #3 ·
at first i thought it was a double pumper, but there isn't any fuel mixture screws for the back, and there is no squirt. there is a place where the back gas squirter could mount identical to the front, but the back squirt hole isnt even threaded and squirts no gas when i open the ports. i removed the rig i had and now its fine. however, shouldn't the back ports open at full throttle?if not, what's the advantage of this carb over a 2 barrel?i've never owned a holley before so its kinda new to me.
 

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Discussion Starter · #4 ·
yeah i guess it is vacuum secondaries
 

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my holley 600 w/ electric choke is sputtering, hesitating, and finally takes off when i floor it. the back two valves on the throttle body wouldn't open when i pushed the acclerator, the little brass arm(don't know the name) that is supposed to open them doesn't seem to be working.i rigged the arm so it would open them and when it idles it revs fine. but in gear it hesitates a lot. is it getting to much air now?
get something other than a holley:thumbup
 

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Discussion Starter · #6 ·
nice pics and vids bearfoot. any suggestions on a new carb? the carb works okay, and its pretty new. the previous owner installed it just before i bought it. but the secondaries dont seem to be opening up, even at full throttle. also what cfm rating can my 351m handle? i don't wanna go bigger than my motor can handle.
 

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Discussion Starter · #7 ·
doh! did a little research and found out secondaries won't open in neutral, not enough load. so that answers that. but does anyone know what would cause it to stall out when i punch the gas and let off to fast in drive?
 

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to much gas not enough air.check for vac leaks tha air fuel mixture might be to high.allways been a problem with any carb i've ever had or messed with that was old
 

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If the timing set is stock, replace it with a straight up (zero degree) timing set and see if that helps. Stock cam timing is 8* retarded for smog and kills the performance on these motors.
 

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Is the accelerator pump working? Those symptoms sound like it's not. It should give an extra shot of gas as the throttle
is opened to compensate for the lag as you change from part to full throttle.

If you look down the carb (Key off) & open the throttle slowly, you should see a steady stream of fuel as the throttle opens.
If you don't, or it's erratic, check the accelerator pump or it's passageways. Sometimes it's just a bad diaphram.

It's the little square with 4 screws on the bottom of the bowl, in this pic the linkage with the red spring pushes on it's arm.
 

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Discussion Starter · #11 ·
thanks el kabong. i checked out the gas stream and its a nice steady stream when i open the throttle so i believe the acc. pump is working properly.i haven't messed with the stock timing yet so maybe it needs to be set to straight up timing. i'm not sure but maybe if the timing is retarded it's causing the engine to stop like that. as long as i stay into the throttle it's fine, it's when i push the pedal in and let off real quick from a stop the engine stalls out.
 

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I have the 650cfm version, but same carb just a little larger on my 400M. Mine did the same thing and I corrected it by using a more aggressive pump cam on the throttle shaft. I forget what color the stock one was, but I ended up using the brown pump cam and in the #1 position. I kept the same size squirter. I did try a bigger squirter from a #31 to #35, but it was too much fuel when pumped. You can buy the assortment of pump cams from summit, jegs, etc...

Kirk
 
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