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I've got a stock out of the box Holley #80457S 600 CFM with VS on my 351C. Timing is set at 14 with 20 more coming in at around 3000 rpm. With the engine warmed up and the choke open, if I hit the gas in drive it'll bog down a bit and then recover. If I don't back off when it bogs, the carb will backfire. I'm assuming I need to tune the carb, but I'd like some suggestions as to where to start, etc. Additional info on the engine is a Crane cam with [email protected] (single pattern), LS of 112 and 508 lift. Pertronix, full length headers into 2.5" exhaust. Stock C4 and 3.00 open rear.
 

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I think your carb problem is not tuning but the carb is too small. My 351C is very much the same setup as yours and I run a 750. I had a 650 but it runs much better with the extra cfm.
 

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Is it a -1 model or what? If its a -1 you probably need to go up some on the primary jets and it also probably needs a different power valve.
 

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the first thing I would check the float levels. if they are right then look for a vacume leak. It sounds like its loading up with gas. make sure every thing is tight and set to the right torgue (intake and carb). is the car hard to start after it dies? is it a brand new carb? are you running high test gas?
 

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Thanks for the timing specs, Shep. I have used both a Holley 600 VS and an Edelbrock 600 with no bogging problems. You might try changing jets, but since I am running the same basic set-up, I wouldn't think that is the problem. Once you set the floats in the Holley, it should work fine (unless the floats are stuck open). Are you getting good fire from the distributor?
Is your trans kickdown working? If you jam the pedal without the trans down-shifting, the C feels dog-lazy.
 
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