CLASS RACER FORUM - View Single Post - Current GM Q-jet Rules

Travis Miller · 03-01-2017, 12:54 PM

Time for a history lesson.

A long time ago in teardown the Q-Jets had the top removed to see if all the plastic pieces were still there. Later we were told not to remove the top, only look at appearance and then measure the venturi and throttle bore. Research showed there was a change in shape of the Q-Jet in 1975. It was ruled that 1965 -1974 looked similar except for fuel line inlet and were called early design. Side inlet could not be swapped with straight inlet and visa-versa. 1975 and newer style had to remain that way including fuel inlet location.

Then came the polished secondary controversy. After a famous carb builder started selling Q-Jets with completely polished secondaries, we were instructed to look for any sign of casting flash removal or even the slightest scratch. Because of that ruling, a lot of Q-Jets failed teardown leading up to the famous "carburetor toss" at the Gatornationals. When a well known S/S racer's Q-Jet failed teardown, he walked over to the ditch behind the tech trailer and threw his high dollar carburetor in the creek. It was soon retrieved by another S/S racer's crewman who wadded into the green slime and picked it up.

Eventually the early vs late ruling was lifted and any year Q-Jet was allowed. So was the fuel inlet location lifted. Only correct venturi and throttle bore sizes for engine/year remain in effect. As with all make carburetors, no flash removal or polishing is allowed anywhere. The 2017 NHRA rulebook in Stock spells out what is allowed and what is not allowed.

03-01-2017, 12:54 PM	#1
Travis Miller Member Join Date: Jun 2007 Posts: 478 Likes: 1 Liked 276 Times in 27 Posts	Re: Current GM Q-jet Rules Time for a history lesson. A long time ago in teardown the Q-Jets had the top removed to see if all the plastic pieces were still there. Later we were told not to remove the top, only look at appearance and then measure the venturi and throttle bore. Research showed there was a change in shape of the Q-Jet in 1975. It was ruled that 1965 -1974 looked similar except for fuel line inlet and were called early design. Side inlet could not be swapped with straight inlet and visa-versa. 1975 and newer style had to remain that way including fuel inlet location. Then came the polished secondary controversy. After a famous carb builder started selling Q-Jets with completely polished secondaries, we were instructed to look for any sign of casting flash removal or even the slightest scratch. Because of that ruling, a lot of Q-Jets failed teardown leading up to the famous "carburetor toss" at the Gatornationals. When a well known S/S racer's Q-Jet failed teardown, he walked over to the ditch behind the tech trailer and threw his high dollar carburetor in the creek. It was soon retrieved by another S/S racer's crewman who wadded into the green slime and picked it up. Eventually the early vs late ruling was lifted and any year Q-Jet was allowed. So was the fuel inlet location lifted. Only correct venturi and throttle bore sizes for engine/year remain in effect. As with all make carburetors, no flash removal or polishing is allowed anywhere. The 2017 NHRA rulebook in Stock spells out what is allowed and what is not allowed.