Q-jet secondary metering rod question

Rusty Davenport · 05-11-2017, 08:18 AM

When an engine is at idle and there is no movement of the secondary metering rods or likewise the hanger, is the secondary metering rods having any effect on the fuel mixture as far as how rich or lean the engine is idling ??? Another way of asking--- are the secondary rods doing anything at idle ???

Greg Reimer 7376 · 05-11-2017, 10:07 AM

No. All fuel that goes past the secondary metering rods goes out the discharge nozzles under the secondary air valve blades. For any air velocity to occur there, the secondary throttle butterflies in the carb base plate have to be open. If air is passing through the secondary side of the carburetor, the butterflies have to be open, so if your engine is idling and a small air flow can be detected at the secondaries, they must not be seated.Check and see if they are hanging open.

Daran Summerton · 05-11-2017, 10:39 AM

Yes it will affect idle usually when float is high or pressure high. So does needle and seat size. Why I don't know.

Rusty Davenport · 05-11-2017, 12:00 PM

Thanks to all who provide input.......I am still experimenting with making the 2 step work with a quadrajet without sacrificing ET. I am trying some low rpm stuff instead of WOT......thanks again.

Kevin Panzino · 05-11-2017, 06:02 PM

Check your PM's Rusty....

Kevin

Everett Vassar · 05-12-2017, 12:35 AM

We are still struggling with the transition from Holley to QJ. At dallas the EGT logger recorded 1544 deg which I thought was lean. I pulled the rods and went to see Mr Braswell. He handed us a pair about 4 sizes smaller and said go try these. Did not improve E.T. did not drop EGT either. But Dustin said the car was acting a little stubborn starting and cruising to the lanes. I noticed he was struggling with staging.apparently some fuel was getting past the rods.. so the old rods went back in. I should have our other Qjet back from Deano this week

Hacksaw · 05-12-2017, 12:00 PM

Rusty: Take the top off a QJ and half fill the fuel bowl and no fuel will run out. It needs passing air to pull the fuel up and out. The secondary rods should have no effect on idle, unless the back blades are not fitting the base plate. Everett: Don't know your combo and yes 1544 degrees sounds lean, but if you have a low compression pkg. it may not be. My EGT probes are close to the flange and mid 1500's are common for me.

Greg Reimer 7376 · 05-13-2017, 08:02 PM

Seems to me that if anything going on in the secondary side of the carb at idle is affected by metering rods or any associated parts, there's fuel entering the engine from somewhere. All the good carb builders use a large needle and seat, the small ones are OEM or equivalent. If a float is too high, and there's excessive gas entering the engine at idle,the engine would go richer and richer until it noticeably blubbers and stalls. In order for a secondary rod to affect that, there would have to be a condition where secondary throttle butterflies in the carb base must not be seated,and they are leaking air,adversely affecting idle quality. Secondary metering rods would not come into play until the secondary air valves opened and lifted the rods out of their seats. Reset the float height,confirm that the needle and seat are not leaking, keep fuel pressure around 5-6 pounds, confirm that the secondary throttle butterflies are shut nice and correctly, this thing should work if all the basics are right.

05-11-2017, 08:18 AM	#1
Rusty Davenport Senior Member Join Date: Jun 2005 Location: Nashville N.C. Posts: 505 Likes: 4 Liked 100 Times in 26 Posts	Q-jet secondary metering rod question When an engine is at idle and there is no movement of the secondary metering rods or likewise the hanger, is the secondary metering rods having any effect on the fuel mixture as far as how rich or lean the engine is idling ??? Another way of asking--- are the secondary rods doing anything at idle ??? __________________ NHRA AND IHRA STOCK ELIMINATOR 2772

05-11-2017, 10:07 AM	#2
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,130 Likes: 172 Liked 698 Times in 216 Posts	Re: Q-jet secondary metering rod question No. All fuel that goes past the secondary metering rods goes out the discharge nozzles under the secondary air valve blades. For any air velocity to occur there, the secondary throttle butterflies in the carb base plate have to be open. If air is passing through the secondary side of the carburetor, the butterflies have to be open, so if your engine is idling and a small air flow can be detected at the secondaries, they must not be seated.Check and see if they are hanging open.

05-11-2017, 10:39 AM	#3
Daran Summerton Senior Member Join Date: Jun 2003 Location: Las Vegas nv Posts: 600 Likes: 18 Liked 66 Times in 37 Posts	Re: Q-jet secondary metering rod question Yes it will affect idle usually when float is high or pressure high. So does needle and seat size. Why I don't know. __________________ 72 cutlass Last edited by Daran Summerton; 05-11-2017 at 10:49 AM.

05-11-2017, 12:00 PM	#4
Rusty Davenport Senior Member Join Date: Jun 2005 Location: Nashville N.C. Posts: 505 Likes: 4 Liked 100 Times in 26 Posts	Re: Q-jet secondary metering rod question Thanks to all who provide input.......I am still experimenting with making the 2 step work with a quadrajet without sacrificing ET. I am trying some low rpm stuff instead of WOT......thanks again. __________________ NHRA AND IHRA STOCK ELIMINATOR 2772

05-11-2017, 06:02 PM	#5
Kevin Panzino Senior Member Join Date: Oct 2002 Location: Pittsburgh Posts: 571 Likes: 288 Liked 738 Times in 134 Posts	Re: Q-jet secondary metering rod question Check your PM's Rusty.... Kevin

05-12-2017, 12:35 AM	#6
Everett Vassar Member Join Date: Jun 2004 Location: Kennedale,Tx Posts: 227 Likes: 0 Liked 2 Times in 2 Posts	Re: Q-jet secondary metering rod question We are still struggling with the transition from Holley to QJ. At dallas the EGT logger recorded 1544 deg which I thought was lean. I pulled the rods and went to see Mr Braswell. He handed us a pair about 4 sizes smaller and said go try these. Did not improve E.T. did not drop EGT either. But Dustin said the car was acting a little stubborn starting and cruising to the lanes. I noticed he was struggling with staging.apparently some fuel was getting past the rods.. so the old rods went back in. I should have our other Qjet back from Deano this week

05-12-2017, 12:00 PM	#7
Hacksaw Senior Member Join Date: Sep 2016 Posts: 875 Likes: 192 Liked 300 Times in 168 Posts	Re: Q-jet secondary metering rod question Rusty: Take the top off a QJ and half fill the fuel bowl and no fuel will run out. It needs passing air to pull the fuel up and out. The secondary rods should have no effect on idle, unless the back blades are not fitting the base plate. Everett: Don't know your combo and yes 1544 degrees sounds lean, but if you have a low compression pkg. it may not be. My EGT probes are close to the flange and mid 1500's are common for me.

05-13-2017, 08:02 PM	#8
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,130 Likes: 172 Liked 698 Times in 216 Posts	Re: Q-jet secondary metering rod question Seems to me that if anything going on in the secondary side of the carb at idle is affected by metering rods or any associated parts, there's fuel entering the engine from somewhere. All the good carb builders use a large needle and seat, the small ones are OEM or equivalent. If a float is too high, and there's excessive gas entering the engine at idle,the engine would go richer and richer until it noticeably blubbers and stalls. In order for a secondary rod to affect that, there would have to be a condition where secondary throttle butterflies in the carb base must not be seated,and they are leaking air,adversely affecting idle quality. Secondary metering rods would not come into play until the secondary air valves opened and lifted the rods out of their seats. Reset the float height,confirm that the needle and seat are not leaking, keep fuel pressure around 5-6 pounds, confirm that the secondary throttle butterflies are shut nice and correctly, this thing should work if all the basics are right.