Eliminating power piston/primary rods?

[10132]

Anyone tried setting up a Quadrajet to run on the primary jets without the primary rods?

[77cruiser]

I did one for a guy that had a pure stock circle track car but he never told me if it worked out.
I did try it on my car before I gave it to him & it ran real good.

[GTO Geoff]

Would be rich in cruise mode. That may foul the plugs such that you get misfire when you go to WOT. Why would you eliminate a system that WORKS?

[rgalajda]

Are you thinking a street car?

The only factory car that did this was an Oldsmobile 1970 W30 455 and W31 350 , 4 speeds. They used smaller main jets. I believe..057 or .058 primary , AU (.0530) secondary rods.These were the small main bleed carbs. Camshafts produced low idle vacuum. In contrast the automatic W30 used a .069 or .070 main jet and 52C metering rod. Did not work out well for the street as GTO Geoff mentioned.

This would not be an advantage for circle track or road race. Think of a caution lap. Some drag race cars have used this with success, but it was more about simplicity for setup. A drag race car only has to deal with wide open throttle and drive back to the pits.

If you have ever had the chance to drive a car with a carter or quadrajet carb running an AFR gauge you would be able to witness what air/fuel ratio should look like. Some people would be amazed.
I dare not include the Edelbrock carb , because I have seen some out of the box that are stupid rich.

[GTO Geoff]

I came across a real odd-ball QJ that had very small pri jets. Mid 1970s carb from memory. Also going on memory, pri jet was 64. Cliff Ruggles gives it a brief mention in his book & says avoid them, they are hard to tune, get another QJ. Ok in a country where there are plenty to choose from....

This particular carb had what seemed like an additional chamber with a single jet, large piston & spring that added fuel to the primary main cct.
Standing in front of the car, the chamber was on the left front with a raised dome.

[rgalajda]

Like this?

[10132]

…thanks for the fast info/ replies…I was just curious as it’s been mentioned by Cliff but no info…I suppose the power piston could be left in its channel and just remove the primary rods?

[GTO Geoff]

Yep, like that. The QJ was replaced with a TQ.....& the owner has never been happier.