Distributor/Carburator Woes

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Joined
Oct 9, 2019
Messages
71
Reaction score
53
Location
Melbourne, FL
My Car
73 Grande, 351C
I've finally got the Grande up and running after swapping out the FMX for a top loader. However, it's running crappy. It was modified in a speed shop before I got it and was rated at 350hp. My mistake in not getting the rebuild specs. That being said, I installed a new Holley 600 with vacuum secondaries and has a stock Motorcraft 12127 distributor with Pertronix upgrade and Flamethrower coil. Fires right up at 10degrees BTC. No hesitation in acceleration when easing on the pedal but hesitates when jumping on it in each gear. Acceleration rate is terrible. I have stock 2.79 gears, but with 350hp, should light up. I set the accelerator pump as per Holley directions and the float level is correct. Also increased the accelerator pump nozzles to a 35 from a 31. Vacuum at idle is just over 15. The carb power valve is stock at 6.5. Now for the interesting part - the timing is set at 10BTC for #1 cylinder, but the opposing cylinder shows 12BTC. The end play on the distributor shaft I measured at .04 (not positive on what the tolerance should be) with no wobble side to side but I noticed the rotor contact is scraping the top of the cap at each point. I thought the Pertronix magnet might be a tad too thick where the rotor sits but I put a caliper to it and the measurement is OK. Also of note, I have a small fuel pressure gauge screwed into the chrome fuel line to the Holley and it reads 9psi. Seems odd since I have a stock mechanical fuel pump. The plugs are black indicating too rich but all I've read says the hesitation is from being too lean. I'm trying to fit this puzzle together between issues with the distributor, carb and timing. Any ideas?
 
dawson357,
Start with the fuel pressure, 9 psi is too high for the Holley 600 vac.
it needs to be 6psi, then recheck and adjust float levels, idle speed and mixture.
then re-evaluate the accelerator pump.
have no clue what you mean by checking timing on the opposing cylinder.
Boilermaster
 
What boiler said, to add on. Make sure your throttle blades are squared off on the transfer slot, instead of having way too much curb idle or too little, can cause a hesitation. Holleys cannot take a lot of fuel pressure so that is #1 priority. Set initial timing to where the engine likes with the squared off throttle blades, make sure you check all in timing so you aren't too high or too low. Also stock fuel pumps are generally rated too high, at least in the world of 70s gm replacement parts, no experience on ford, 9-10 is pretty normal despite a quadrajet (or any other carb) struggling with anything more than 6. You could also peak your head over the venturies and make sure the fuel is atomizing instead of dripping. Also make sure the car is properly warmed up before messing with anything, your location is Florida so prob not as crucial but every little bit helps.
 

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