Q jet primary jetting?

Dean Oliver · 10-14-2008, 08:19 AM

Lyn,

The math tells you to go between .004 and .005 smaller. I go .004 smaller, so if you were running .072 jets with rods you would run .068 jets without. (That assumes you have .026 tip primary metering rods.)

Dean

Alan Roehrich · 10-14-2008, 08:21 AM

The question is, SHOULD you remove the metering rods?

Dean Oliver · 10-14-2008, 08:34 AM

Alan,

There is no performance advantage to removing the rods, unless the power system has not been properly set up for a racing application. Removing the primary rods basically just makes the Q-jet easier for the average tuner to disassemble and, particularly, re-assemble. On my car and many others, we have seen no improvement in ET anywhere down the track when converting to the "no rod" set up in the primary. But ask most racers what they don't like dealing with the most on Q-jets and usually they will tell you the power piston installation. Some racers never change their primary jetting because of it.

Dean

Mike Pearson · 10-14-2008, 11:30 AM

Dean,

What do you do with the hole where the plunger used to be? Or do you just leave the plunger and remove the rods?

Dean Oliver · 10-14-2008, 01:58 PM

Mike,

The piston can be left in the carb with the rods removed, but that still leaves you with the potential to tear the top gasket when working on the carb. I would recommend either plugging the piston bore with a "freeze plug" type plug or with a shallow 3/8" setscrew. That way you don't have to worry about damaging the top gasket when you are removing or installing it around the power piston which no longer serves any function with the rods removed.

Dean

Alan Roehrich · 10-14-2008, 02:09 PM

Dean,
Thank you VERY much for taking the time and effort to reply. The only thing that bothers me about fooling with a Q-Jet these days is not being able to find good genuine Rochester parts. I have a very finite supply of jets, metering rods, hangars, and power piston springs. I try to pick up GM Delco stuff when I can, I've got a Delco 76150 kit in the trailer, and I keep a tackle box of parts handy.

Mike Pearson · 10-14-2008, 02:15 PM

Dean,Thanks For the info. What is your contact info. I have a couple of 207's that need some work. You can e-mail it to me if you like ssia2485@yahoo.com

10-14-2008, 08:19 AM	#1
Dean Oliver Junior Member Join Date: May 2002 Location: Stuttgart, AR Posts: 53 Likes: 1 Liked 0 Times in 0 Posts	Re: Q jet primary jetting? Lyn, The math tells you to go between .004 and .005 smaller. I go .004 smaller, so if you were running .072 jets with rods you would run .068 jets without. (That assumes you have .026 tip primary metering rods.) Dean Last edited by Dean Oliver; 10-14-2008 at 08:22 AM.

10-14-2008, 08:21 AM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,132 Likes: 1,600 Liked 1,912 Times in 429 Posts	Re: Q jet primary jetting? The question is, SHOULD you remove the metering rods? __________________ Alan Roehrich 212A G/S

10-14-2008, 08:34 AM	#3
Dean Oliver Junior Member Join Date: May 2002 Location: Stuttgart, AR Posts: 53 Likes: 1 Liked 0 Times in 0 Posts	Re: Q jet primary jetting? Alan, There is no performance advantage to removing the rods, unless the power system has not been properly set up for a racing application. Removing the primary rods basically just makes the Q-jet easier for the average tuner to disassemble and, particularly, re-assemble. On my car and many others, we have seen no improvement in ET anywhere down the track when converting to the "no rod" set up in the primary. But ask most racers what they don't like dealing with the most on Q-jets and usually they will tell you the power piston installation. Some racers never change their primary jetting because of it. Dean

10-14-2008, 11:30 AM	#4
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,464 Likes: 622 Liked 1,956 Times in 591 Posts	Re: Q jet primary jetting? Dean, What do you do with the hole where the plunger used to be? Or do you just leave the plunger and remove the rods? __________________ Mike Pearson 2485 SS

10-14-2008, 01:58 PM	#5
Dean Oliver Junior Member Join Date: May 2002 Location: Stuttgart, AR Posts: 53 Likes: 1 Liked 0 Times in 0 Posts	Re: Q jet primary jetting? Mike, The piston can be left in the carb with the rods removed, but that still leaves you with the potential to tear the top gasket when working on the carb. I would recommend either plugging the piston bore with a "freeze plug" type plug or with a shallow 3/8" setscrew. That way you don't have to worry about damaging the top gasket when you are removing or installing it around the power piston which no longer serves any function with the rods removed. Dean

10-14-2008, 02:09 PM	#6
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,132 Likes: 1,600 Liked 1,912 Times in 429 Posts	Re: Q jet primary jetting? Dean, Thank you VERY much for taking the time and effort to reply. The only thing that bothers me about fooling with a Q-Jet these days is not being able to find good genuine Rochester parts. I have a very finite supply of jets, metering rods, hangars, and power piston springs. I try to pick up GM Delco stuff when I can, I've got a Delco 76150 kit in the trailer, and I keep a tackle box of parts handy. __________________ Alan Roehrich 212A G/S

10-14-2008, 02:15 PM	#7
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,464 Likes: 622 Liked 1,956 Times in 591 Posts	Re: Q jet primary jetting? Dean,Thanks For the info. What is your contact info. I have a couple of 207's that need some work. You can e-mail it to me if you like ssia2485@yahoo.com __________________ Mike Pearson 2485 SS

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