holley question
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Senior User
Joined: Jul 2009
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From: Sainte Genevieve, Mo
holley question
Ok .. I have a mildly built 302 .040 over, 292 cam, air gap intake. holley carb 600
my problem/question is this. .. when I ease into the throttle and take it up to about 3200 rpm the 4bbl opens and studders for a second or two then picks up.. NOW up to that point it will run like a banshee if ya want it to until that point then it will pick back up again but with not as much ummmph..
any suggestions to get me started on fixing this or heck if you know the exact problem shout it out.. please.. thanks
C
my problem/question is this. .. when I ease into the throttle and take it up to about 3200 rpm the 4bbl opens and studders for a second or two then picks up.. NOW up to that point it will run like a banshee if ya want it to until that point then it will pick back up again but with not as much ummmph..
any suggestions to get me started on fixing this or heck if you know the exact problem shout it out.. please.. thanks
C
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Joined: Sep 2003
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From: SoCal
I'm interested in this thread too, as I have a similar situation, except that my car is just sluggish right now. I have a Holley 1850 600 cfm vacuum secondary, straight out of the box with no modifications, but just rebuilt. The cam is a Comp Cams FE268H-10, 268/268 @ .006 or 219/219 @ .05, .456/.456 gross lift. The thing is slow to pick up from stand still, and slow to pick up from a roll. It may still stumble occasionally from flooring the gas pedal. So, the carb needs some kind of tuning, but I don't know how to start.
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I will say this is way easier with a vac guage and a air/fuel meter.... a vac gauge is cheap... but a good air/fuel meter like a fast is a 300 dollar deal.... start with lean to best idle.... holley says set the idle circuit needles 2.5 turns out.... well mine are1.5 turns out... take the vac guage and connect to a manifold vac port and turn for highest idle vacuum.... try this and then drive around the block and read a plug... then onto primary jet sizing.... holley usually puts in 64 jets..... which depending on your timing and cam could be to big or too small.... then look at the vac seconday spring..... it could be too heavy or too light.....
to answer the question of the first poster.... if this is the only time you experience this start by going up a jet size.... first check you initial jets and then buy the net two larger sizes..... also a quick change for the vac secondary spring can help and a set of springs ... you might want a lighter spring to open the secondaries faster.....
to answer the question of the first poster.... if this is the only time you experience this start by going up a jet size.... first check you initial jets and then buy the net two larger sizes..... also a quick change for the vac secondary spring can help and a set of springs ... you might want a lighter spring to open the secondaries faster.....
Thread Starter
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Senior User
Joined: Jul 2009
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From: Sainte Genevieve, Mo
Ive got mine idleing at 650 rpm. pulling 23 on the vacuum gauge.. everything is working like it should as per the gauge.. Ohh my carb is a vacuum secondary carb. I have noticed one thing.. I adjusted my timing down to 8.5 adv. the stumble / miss moved with it. I am inclined to think that its in relation to spark. SO im changin out my brain box tomorrow morn.. let yall know if this works..
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Joined: Jan 2010
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From: Great Falls Mt
I only get 14 to 15 on the vacuum gauge...351w, WAS a 93 efi, now has a cast iron intake and holley/motorcraft 4bbl, still has serp belt so im pretty positive the cam is still stock...think I have a vacuum issue?
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Elder User
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cOpE!...... as long as the truck runs fine..... you do not have a vac issue.... what you can do is the lean to best idle thing where you lean out the idle mixture screws until the engine stumbles a little and then back them out 1/4 to 1/8 turn and drive the thing and check the plugs, and see if they read okay..... vacuum is dependent on cam timing etc... so i woudnt tell you to tune for vacuum alone....
