Racing Fuel Systems

If I remember correctly, I believe that jmarkaudio once posted here or somewhere else that he had done a 2-circuit conversion to a Holley 1425 Dominator (0-80911) and that it worked very well for him. I'm running that same carburetor on a naturally aspirated 548 BBC that will be running at Drag Week on Monday. I leave from California very early Thursday morning. So, time is getting very short and I'm getting a bit desperate. It was my understanding that the out-of-the-box calibration for the 1425 is pretty bad so I went straight to the 2-circuit conversion while trying to make a sort of educated guess at the calibration. Unfortunately, I think my guestimated calibration is out in left field. So, I was hoping that jmarkaudio would take pity on me and suggest a good starting point for a calibration on the 2-circuit 1425. If anyone else has experience with that carburetor, feel free to chime in if you want. Any help would be greatly appreciated.

I have also run the car with a 1050 Dominator (8896) that has also undergone a 2-circuit conversion. Although that carburetor still needs a little tuning, its calibration is much closer than the 1425 and it runs much better at the moment. I may end up using the 1050 instead.

Just wondering which 2 circuit blocks you used to feed that monster lol.

That's a big carb for a single 4 barrel 548" engine. Maybe the calibration is not the issue?

The metering blocks I'm using are BLP 51251-5 with the angle channels drilled to 0.169"

bigblockmark - You may be correct. The 1425 may be to big for my combination. The car is supposed to have a 6000 rpm stall speed converter (seems tighter) and I'm planning on eventually turning it 7800. Drag Week is going to wind up being a big test-n-tune for me. lol All that being said, I think it's too early to dismiss the carb as too big. However, if it can be sorted out it will take some time. That's why I'm hoping to get some insight on a baseline calibration.

Anything I do on that requires new metering blocks and I replace the boosters. You need metering blocks 2 or 3 circuit without idle tubes.

jmarkaudio - Thanks for the reply. I used my 1050 for Drag Week but I would still like to to sort out this 1425. For the 2-circuit conversion, I did use new 2-circuit metering blocks without idle tubes. The metering blocks I'm using are BLP 51251-5 with the angle channels drilled to 0.169". The main wells are as they came from BLP. Do I need to make them larger? As for the boosters, I did not change them but I am willing to do so. Are the boosters something that I can purchase from you? Thanks again. Any help that you or anyone else provides is really appreciated.

I sent my 1250 to Mark Whitener (jmarkaudio) to have his custom boosters installed. He also provided the BLP wide body metering blocks set up for 2 circuits. Best money I have spent on a carburetor. Been using it for 5 years now on a 582 BBC.

bigblockmark - Did Mark post some pics of that build? If so, I think I remember seeing them. Although I tend to be a do-it-yourselfer (I learn more that way), I'm certainly not opposed to sending him my 1425 to sort out. I'm discovering that I don't have the time to do everything myself.

I do not remember seeing a post on that carb. It is black/gray one coated from Holley. Has black anodized wide body metering blocks from BLP that Mark further modified. His boosters have special machining and more smaller holes than most you see. As far as being a hands on type guy, I am with you there. I do Holley carbs often for locals and build my own engines and a few for friends. I don't think you can do the boosters yourself and that is why I sent the carb to Mark. He has the tool to press out and in. Plus, his personal experience is golden as far as putting those details into a build. He helped me thru the 2 circuit conversion logic, the Av Gas deal and the lower idle restrictor conversion reasoning.