General Category > Quadrajet Carb Talk and Tips
1973 800 CFM Mods
Jim Rodgers:
First off, hi everyone.
New here but have found lots of interesting and beneficial information. Gonna see if I can post a pic of my qjet to see if I can get some feedback/ideas.
Jim Rodgers:
And the bottom.
Jim Rodgers:
I will start by saying I do not consider myself an expert when it comes to carbs, much less q-jets. The work I have done to this carb has progressed slowly over time (3-4 years), and I feel like it runs as good as it does in spite of the work I have done to it, not because of the work I have done to it.
Second, this is a factory stock appearing 455 Buick race engine, 540 ci, roller cam, factory iron manifolds in a factory stock appearing 70 GS Stage 1 at 3770 race weight. The car isnt driven on the street, it is a 1/4 mile car.
You can see I have removed the front part of the choke horn, but I left the rear portion for fear the secondaries would pull fuel from the primaries. I removed the outer ring from the primary squirter, and ported the primary venturi and installed the larger Holley butterflies. I also ported the rear venturi, and installed butterflies I made myself out of aluminum sheet. (They dont make a perfect seal with the base plate so care has to be taken to set idle speed or you start pulling open the secondary air flaps) I trimmed down the throttle shafts. It has 88 jets in the front with no metering rods, and the smallest rods in the rear that I could find.
I have the bigger needle and seat and I have opened up the factory carb inlet fitting to 1/2 inch.
Jim Rodgers:
Fuel cell in trunk, -12 to Magnaflo 500, -10 to Magnaflo 2 port regulator, (2) -6 to a Y block, then 1/2" line to the factory fuel pump that has been gutted and the 1/2" line loops out and connects to the factory 3/8" line and goes up to the carb. This setup will pump a gallon to the carb inlet in 15 seconds.
I have an O2 sensor on the car and it has always been lean, but the past couple times out we have been able to richen it up with the bigger jets and removing the primary metering rods.
The car idles pretty nice and never, ever stumbles. It always runs clean on every pass, no hesitation or miss.
The car has been a best of 10.23 at 127 and change, 1.37 60'.
I feel like it should run more MPH. In high gear it acts like it is just lopeing along. No converter troubles and the trans is good. I know I have iron exhaust manifolds and that certainly doesnt help MPH matters, but I cant help buit feel it is due better MPH.
Jim Rodgers:
Fuel system.
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