Edelbrock QJet 1901 Rebuild/Tuning Questions
07-09-2006, 09:41 PM
#1
Melting Slicks
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St. Jude Donor '11-'12-'13,'19-'20
Edelbrock QJet 1901 Rebuild/Tuning Questions
Greetings,
So my QJet rebuild project is underway. Got the thing disassembled and cleaned up, and have begun re-assembly. I am using the Ebrock rebuild kit and also have the tuning kit.
Motor is a 350-250 crate, factory stock with a Ebrock 2101 intake, 2 1/2 pipes w/ Flowmaster delta 50's.
The 1901 came with 69/36 primary jet/rod combination which was way lean. This is the primary reason I am doing this. The carb otherwise was working great, but starving the engine at mid-high rpm.
I am beginning with a 73/41 set.
Q: Any opinions on this? The other option is 75/43.
On the secondaries, the rod's that were removed are marked DR. No DR in the new kit. The options are:
CC, CE, CK,AY,CL. For the hanger, the otions are:
"B" (.520) "G" (.545), "K" (.565), "P" (.590) and "V" (.165)
Q: What would be a good starting combo for these? I was planning to start in the middle with CK/K
Power piston springs range from 4-8in-hg. I plan to start with orange which is the 5.
Any guidance that would help me get it close the first time would be appreciated.
I also hope I can get the choke back together. (Yikes)
So my QJet rebuild project is underway. Got the thing disassembled and cleaned up, and have begun re-assembly. I am using the Ebrock rebuild kit and also have the tuning kit.
Motor is a 350-250 crate, factory stock with a Ebrock 2101 intake, 2 1/2 pipes w/ Flowmaster delta 50's.
The 1901 came with 69/36 primary jet/rod combination which was way lean. This is the primary reason I am doing this. The carb otherwise was working great, but starving the engine at mid-high rpm.
I am beginning with a 73/41 set.
Q: Any opinions on this? The other option is 75/43.
On the secondaries, the rod's that were removed are marked DR. No DR in the new kit. The options are:
CC, CE, CK,AY,CL. For the hanger, the otions are:
"B" (.520) "G" (.545), "K" (.565), "P" (.590) and "V" (.165)
Q: What would be a good starting combo for these? I was planning to start in the middle with CK/K
Power piston springs range from 4-8in-hg. I plan to start with orange which is the 5.
Any guidance that would help me get it close the first time would be appreciated.
I also hope I can get the choke back together. (Yikes)
07-10-2006, 01:01 AM
#2
Drifting
First of all, don't worry about the secondaries just now. You're going to tie them closed anyway. This is so you can work on only one side of the carburetor at a time.
As long as the engine will idle and run at low speeds acceptably the base tune on the primary side should be a 73/43 combo. This will allow the engine to behave well enough for you to make some timed runs. As long as you can roll into the throttle without the engine protesting too much this will be good enough.
The first thing you will tune will be the primary jet size. This is WOT tuning so you will need to find a strait, level section of road where you can safely accelerate between 35 and 60 MPH. Time the car between 40 and 60 MPH in second gear with the throttle on the floor. When you have this data, make a change in main jet size. As long as the times keep getting shorter (accelerating quicker from 40 to 60) you're going in the right direction. When you get to a point where the time gets longer, back up to the previous best jet. This is the main jet that your engine prefers.
NOTE. You may need to adjust the primary rod size during this phase of your tuning to keep the part throttle/cruise clean. The 73/43 combo will give you a cruise metering area of 2.7332 according to Lars' data sheet. If this runs well enough for you to do the rest of your testing you may want to maintain it (or as close as you can get) by changing rods as you search for the correct main jet.
Once you have the main jet size set you will not need to mess with it any more. The next phase of your tuning will be part throttle/cruise metering. This is controlled by the primary metering rods.
Now, while main jet tuning is measured by time, part throttle/cruise is judged more by feel. This is where you need a calibrated butt because that is how your going to feel the engine surging as you get to the lean limits of the PT/C circuit. The general idea is to lean the PT/C out (go larger and larger on the main metering rods) until the engine begins to surge at normal cruising speeds (like 35, 45, 55, and 65 MPH). You keep going larger on the rods until you detect surging at any one of these speeds. Then, if it is not too objectionable, you may be able to adjust the adjustable part throttle (APT) screw to lift the rods out of the jets just enough to cure the surging. Cruise metering has two (2) adjustments, rod size and the APT screw. Surging will be more noticeable at 50 to 60 MPH on the highway when going up a slight incline.
This should give you enough to keep you busy for a while. When you're done with this report back and we'll then work on the accelerator pump. When we're done with that you'll be able to unlock the secondaries and the fun really begins.
BigBlockk
Later.....
As long as the engine will idle and run at low speeds acceptably the base tune on the primary side should be a 73/43 combo. This will allow the engine to behave well enough for you to make some timed runs. As long as you can roll into the throttle without the engine protesting too much this will be good enough.
The first thing you will tune will be the primary jet size. This is WOT tuning so you will need to find a strait, level section of road where you can safely accelerate between 35 and 60 MPH. Time the car between 40 and 60 MPH in second gear with the throttle on the floor. When you have this data, make a change in main jet size. As long as the times keep getting shorter (accelerating quicker from 40 to 60) you're going in the right direction. When you get to a point where the time gets longer, back up to the previous best jet. This is the main jet that your engine prefers.
NOTE. You may need to adjust the primary rod size during this phase of your tuning to keep the part throttle/cruise clean. The 73/43 combo will give you a cruise metering area of 2.7332 according to Lars' data sheet. If this runs well enough for you to do the rest of your testing you may want to maintain it (or as close as you can get) by changing rods as you search for the correct main jet.
Once you have the main jet size set you will not need to mess with it any more. The next phase of your tuning will be part throttle/cruise metering. This is controlled by the primary metering rods.
Now, while main jet tuning is measured by time, part throttle/cruise is judged more by feel. This is where you need a calibrated butt because that is how your going to feel the engine surging as you get to the lean limits of the PT/C circuit. The general idea is to lean the PT/C out (go larger and larger on the main metering rods) until the engine begins to surge at normal cruising speeds (like 35, 45, 55, and 65 MPH). You keep going larger on the rods until you detect surging at any one of these speeds. Then, if it is not too objectionable, you may be able to adjust the adjustable part throttle (APT) screw to lift the rods out of the jets just enough to cure the surging. Cruise metering has two (2) adjustments, rod size and the APT screw. Surging will be more noticeable at 50 to 60 MPH on the highway when going up a slight incline.
This should give you enough to keep you busy for a while. When you're done with this report back and we'll then work on the accelerator pump. When we're done with that you'll be able to unlock the secondaries and the fun really begins.
BigBlockk
Later.....
07-10-2006, 08:21 AM
#3
Melting Slicks
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Member Since: Mar 2006
Location: Piedmont Va
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St. Jude Donor '11-'12-'13,'19-'20
Thanks Big Blockk...I have to work for the man today 
...but will finish assembly this evening and try the first primary run out on the bypass...I'll let you know on progress.
Thanks again...-patrick
...but will finish assembly this evening and try the first primary run out on the bypass...I'll let you know on progress. Thanks again...-patrick
