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Holley Carb Question

1K views 6 replies 4 participants last post by  lluciano77 
#1 ·
Hey guys, I put a 750 vacuum secondary holley on a 454bbc. I,m trying to get the throttle blades closed down on the primary to get full use of the transition slots. The throttle blades are still open about 1 1/2 turns on the stop screw and I have already drilled 1/8 air bypass holes in the front blades. Does anyone know if its ok to drill the holes bigger or will it mess up the signal at the transition slots.

Thanks, Kevin
 
#3 ·
DoubleVision, its a 460ci bbc, dont know compression exactly but its got 225# on a compression gauge. The cam is a extreme energy XE284H, 240-246@.050-.574-.578 and 110 overlap. I'm running straight mechanical advance which I want to modify to get more initial advance. I'm running 15 initial and 38 total. I bumped the initial up as far as 21 degrees and it didnt help idle it down any.
 
#4 ·
are you running a auto tranny? if so does it have a stall converter? what RPM does the engine idle at? raising the spark timing to 21 degree`s total will make it idle up, or help the idle to become more stable, then you should be able to lower the idle at the carb. the cam you have is sizeable, and I would think for that many cubes and that size cam you need at least a 850 carb or larger. it could be that your on the very edge of enough fuel flow at idle from that 750 for that many cubic inches and engine mods.
 
#5 ·
I guess I am not seeing the problem. Are you wanting to run the primary blades totally closed? If so, you could open the secondaries a bit, but that does not make sense to me. 1 1/2 turns from closed is not much, and I cant imagine that it the primaries need to be completely closed.

Just not understanding....

Chris
 
#6 ·
TurboS10, you were right. The throttle blades are where their suppose to be. I pulled the carb off and looked at the transition slots and they were showing about .020 looking from the bottom. I drilled the idle air bleeds .002 yesterday which improved the idle, cruise and some of the exhaust fumes. I still have a small stumble when the throttle is nailed. I havent bumped the timing back up yet to see if the stumble is gone. I have to take some of the 23 degrees of mechanical advance out of the distributor to get the timing I want which is 18-21 initial to 35 total. I looked at a mr gasket HEI curve kit yesterday but it doesnt tell what the mechanical advance is.
 
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