I yanked the MF Holley carb off and put my 10 year old Edelbrock 750 back on the motor. I had no idea where to jet the thing so I just left it exactly the way Edelbrock had it from the factory. The challenge was to improve the driveability and mileage without sacrificing WOT power. The carb is a quick fuel Q750. It is stock other than an edelbrock intake a and a Holley 600 carb. Otherwise this will also cause the engine to bog. I figured since the stumble is pretty bad, swing big and find something out vs going 3 sizes at a time and wasting a bunch of money. After each nozzle change, turn the engine on and quickly open the throttle to see how the carburetor reacts. 1801 Tuning for WOT and carb direction 10-08-2017, 06:09 PM ... Edelbock's, Holley's, and Rochester carburetors are all designed to be forward facing. The Holley accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. I tried 1:1 on the secondary linkage, no bueno, ran terrible. As mentioned earlier, by selecting the correct spring for the vacuum chamber, you take care of 90 percent of the tuning of the secondaries. Going to do it and see what happens. Here's the motor details: 496 hydraulic roller; 245/250 cam w/ 110 LSA; Holley 4150 950CFM carb… Funny it only does this at wot, 3/4 or less, just goes. So, out of curiosity, I put the 750 edelbrock back on. Moderator: Team. But, let's try the cheap simple stuff first. This article leaves out a bunch of detail. Lv 4. The car has a very mild 351C 2V with and Edlebrock Performer, and a 700 Holley double pumper carb. If the stumble turns to bog it’s the idle jets. For a better experience, please enable JavaScript in your browser before proceeding. If you're not real quick on jerking the throttle it'll rev up fine. My history with Holleys tells me that the above replies are correct. The stumble is now greatly reduced, but not completely gone. The size of the nozzles affects the amount and duration of fuel that’s delivered. A lean condition at steady throttle will generally surge. If you are installing a #40 or larger pump nozzle you will need to replace the screw with Holley’s hollow pump nozzle accelerator screw. Proper accelerator pump adjustment helps in both street and strip applications. By: Quick Fuel Technology | 05/18/2010 < Back to Motor Life Home. I have not given up on the Holley. Not all Holley’s have the same ports, but you can tell by location and size what each one does. Here’s where gas mileage can really be improved! BLstangin Member Posts: 171 Joined: Wed May 05, 2010 2:02 am Location: Holley tip in stumble. See all 20 photos. I tried the 50cc pump on front, no improvement there. Critical factors are volume and timing, this has to be tuned to engine demand. It still stumbles, but it's better. Let me tell you what I have so far...388w with afr185 heads and a 238 degree cam and a 2500-2800 rpm stall. I changed one thing at a time and tried it out. I ask because my idle vacuum with the 850 is 14" steady, the 750 is 15.5" steady. If the car hadn't come with a Holley on it I would have bought an Edelbrock carb. World's #1 Racing & Performance Classifieds, May 13, 2014 When I let off the gas to yield or turn a corner it has a dead spot as soon as you step back on the pedal. The reaction that counts is torquing up against the converter, releasing the brake and stabbing the throttle. The WOT air/fuel ratio was only slightly rich at 12.2:1. Today, the iconic Holley four-barrel is both alive and thriving with continuing innovation. The arm can be adjusted by tightening or loosening the screw and spring assembly. Carb Number Carb Model Number CFM Renew Kit. Fuel pressure at 6.5psi. https://www.holley.com/products/fue...l/black_diamond_series/ss-series/parts/BD-850, http://centurylofts.axiscam.net/1970C10/img/HolleyPumpCam.jpg, https://www.tapatalk.com/groups/racingfuelsystems/, VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. I don't know what WOT is but I had a little stumble but it was only if I was to try and pull out slow and not really give it any gas, if I mash it to the floor it would burn tire and go. Q: I can’t get the “Bog” out of my mechanical secondary carburetor what’s wrong and how can I fix it? This tends to maximize the load the engine sees. They also left out the transition circuit. Tuning Your Holley Carb Made Easy. Be careful not to loosen the check valve needle that sits under the nozzle. The carb is a Holley street HP 650 DP (ms). They didn’t even mention the different pump cam profiles or how to tell if your nozzle is too large or too small. 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