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70 LT-1 Holley Carb List 4555 specs.

 
Old 04-09-2007, 01:32 PM
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Default 70 LT-1 Holley Carb List 4555 specs.

I recently purchased one of those new Holley List 4555 carburetors that Holley made a second manufacturing build not to long ago. It was supposed to be identical to the original with only a few minor differences. (bowl bolts, no date code, etc.). I took a leap of faith and made the assumption that it was already set up per factory specs, only to find that it had a pretty severe off idle stumble. The old List 3310 that I had on it ran fine and had #72 primary jets. This last weekend I finally got around to taking a closer look at the new carb only to find #68 jets in the primary. Can anyone point me to the correct configuration and specs for the new carb. I am beginning to wonder if the secondary throttle plates are adjusted correctly at idle allowing the idle transfer metering to take effect.???? I would like to start from a known correct baseline configuration before I start doinking with the shooters, accel pump, cam, power valve etc.

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Old 04-09-2007, 01:57 PM
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Your 4555 should have #70 primary jets and 76's on the sec side. Set it up with this jetting, check and set up your secondary idle speed (get it cracked open so that the primary side is not open more than .020" of t-slot exposure), set float levels, and I'll bet that stumble will go away.
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Old 04-09-2007, 02:08 PM
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Thanks, Lars I am surprised the jetting is off.......makes me wonder about any of the other components. I will check the secondaries as you say.

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Old 04-09-2007, 03:17 PM
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I'm not surprised at all. I've seen incorrect jetting out of the box on both Holley and BG carbs. I've also seen brand new carbs with primary and secondary jetting reversed. You need to disassemble that new carb and check everything. In addition to not being set up right, it likely has a bunch of crap inside it from the manufactruing process. Don't just slap it on and run it.
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Old 10-19-2007, 01:42 PM
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Was there ever a resolution to this problem? I have the same problem with my 4555. 72 primary jets, I've tried 28, 31, and 35 accelerator pump nozzles (I have a 40 to try today), 50cc pump. The engine just can't handle a quick snap of the throttle, which makes downshifting for a corner somewhat scary. The power valves are 6.5 and seem to be ok, but I put some 8.5's in to try anyway. LT-1 cam, installed 4* advanced.

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Old 10-19-2007, 01:52 PM
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Originally Posted by 69autoXr View Post
Was there ever a resolution to this problem? I have the same problem with my 4555. 72 primary jets, I've tried 28, 31, and 35 accelerator pump nozzles (I have a 40 to try today), 50cc pump. The engine just can't handle a quick snap of the throttle, which makes downshifting for a corner somewhat scary. The power valves are 6.5 and seem to be ok, but I put some 8.5's in to try anyway.

yes, turned out the brand new carb I purchased from Chicago Corvette had a bent (or an incorrect) accelerator pump lever. when throttle was accuated, it was not moving the pump arm anywhere near enough. I didn't notice it at first when I manually actuated the throttle, because there was some squirt, albeit not enough.

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Last edited by Bullshark; 10-19-2007 at 02:23 PM.
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Old 12-12-2014, 08:25 AM
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Originally Posted by lars View Post
..................set up your secondary idle speed (get it cracked open so that the primary side is not open more than .020" of t-slot exposure),
More detail please. I am getting too old to remember this stuff.
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Old 12-13-2014, 10:56 AM
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Originally Posted by Big2Bird View Post
More detail please. I am getting too old to remember this stuff.
Just drop me an e-mail request for my Holley carb setup papers - it has the process outlined in detail.

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Old 12-13-2014, 09:38 PM
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Originally Posted by lars View Post
Just drop me an e-mail request for my Holley carb setup papers - it has the process outlined in detail.

Lars
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Done. Thank you old friend. Two old friends in one thread. How cool is that? Even if it's an old thread, it is still pertinent. Happy Holidays guys Bird
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