Fine tuning quadrajet E4ME
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Instructor
Joined: Mar 2014
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From: Frankfort IL
Fine tuning quadrajet E4ME
Ok, so I've rebuilt the carb, new dizzy, new plugs, new wires, hooker super comp headers flowing through 2 1/2" exhaust to dual Flowmaster delta 40's. I've got the basic adjustments done in the carb. It starts right up, idles fine right around 700rpm.it seems to be fairly quick but I feel like I'm still lacking some "oomph" when I go WOT. Can someone please explain the process of fine tuning to get the most performance from the carb. I've rebuilt power the instructions in cliffs book. I'm looking for information on the following :
1. Fine tuning the air / fuel mixture screws
2. Adjusting the APT screw and lean and rich stop screws
3. Adjusting secondary pull off rate
4. Am I missing anything else here?
On the secondaries I'm not sure if I have to make an adjustment to the vacuum dashpot. How can I time how long it takes to release?
The car is an 81 c3. motor has been bored.. 30 over, healthy cam, flat top Pistons. The car sounds great and runs fine, no check engine light. To my knowledge everything is running good, I just feel like it should have a bit more power in there, my gut says it's the carb as I haven't made any "fine tuning" adjustments. I'd love to get this running right. Any help out there? Thanks as always!
1. Fine tuning the air / fuel mixture screws
2. Adjusting the APT screw and lean and rich stop screws
3. Adjusting secondary pull off rate
4. Am I missing anything else here?
On the secondaries I'm not sure if I have to make an adjustment to the vacuum dashpot. How can I time how long it takes to release?
The car is an 81 c3. motor has been bored.. 30 over, healthy cam, flat top Pistons. The car sounds great and runs fine, no check engine light. To my knowledge everything is running good, I just feel like it should have a bit more power in there, my gut says it's the carb as I haven't made any "fine tuning" adjustments. I'd love to get this running right. Any help out there? Thanks as always!
Le Mans Master
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From: charlotte north carolina
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Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
1. Fine tuning the air / fuel mixture screws
SR: With an E4ME, you set the idle mixture screws until you're in the center of the dwell gauge on a 6 cylinder readout. This allows for calibration in either direction.
2. Adjusting the APT screw and lean and rich stop screws
SR: There is no APT screw on an E4ME, just the lean and rich stops. There's a range you want them to travel in, and a baseline for rich stop. You should check around on thirdgen.org, tons of info on tuning E4MEs there.
3. Adjusting secondary pull off rate
SR: This is done by enlarging the restriction. Alternately, you can get ones pre-modified from Cliff Ruggles. I'm either completely inept or it's a difficult process.
These pulloffs require you to straighten the vacuum barb and then slowly drill out the restriction. I usually end up mangling the diaphragm by overheating. Oops. So have Cliff do it.
4. Am I missing anything else here?
On the secondaries I'm not sure if I have to make an adjustment to the vacuum dashpot. How can I time how long it takes to release?
SR: Retract the pulloff link completely with your finger, cover the vacuum source with your finger. Hit "START" on your stop watch and pull your finger off. Hit "STOP" on your stop watch when the link stops moving out.
SR: With an E4ME, you set the idle mixture screws until you're in the center of the dwell gauge on a 6 cylinder readout. This allows for calibration in either direction.
2. Adjusting the APT screw and lean and rich stop screws
SR: There is no APT screw on an E4ME, just the lean and rich stops. There's a range you want them to travel in, and a baseline for rich stop. You should check around on thirdgen.org, tons of info on tuning E4MEs there.
3. Adjusting secondary pull off rate
SR: This is done by enlarging the restriction. Alternately, you can get ones pre-modified from Cliff Ruggles. I'm either completely inept or it's a difficult process.
These pulloffs require you to straighten the vacuum barb and then slowly drill out the restriction. I usually end up mangling the diaphragm by overheating. Oops. So have Cliff do it. 4. Am I missing anything else here?
On the secondaries I'm not sure if I have to make an adjustment to the vacuum dashpot. How can I time how long it takes to release?
SR: Retract the pulloff link completely with your finger, cover the vacuum source with your finger. Hit "START" on your stop watch and pull your finger off. Hit "STOP" on your stop watch when the link stops moving out.
Hope that helps.
Melting Slicks
Joined: Aug 2003
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From: dayton oh
email lars at v8fastcars@msn.com for his excellent paper "Tuning Qjets".
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
Very little of Lars' paper is for E4MEs. The secondary circuit on an E4M may be dealt with the same as the secondary on an M4M. Primary side and idle mixture runs off the ECM and requires a different strategy.
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Instructor
Joined: Mar 2014
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From: Frankfort IL
Awesome response, thanks! I've been reading so much, search after search, etc etc that I completely forgot about setting the dwell! Last night I made a few adjustments to the secondary pull off spring, first two I had bog, the last one seems to have nailed it. I guess next I'll adjust the air fuel mixtures. So should I adjust the for max vacuum or for dwell? I've got both the dwell meter and vac tester so I could do either. I can't remember the name of it now but I know I measured the travel (?) through the top of the carb and I'm right at 2/32. If love to finally get this dialed in!
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Awesome response, thanks! I've been reading so much, search after search, etc etc that I completely forgot about setting the dwell! Last night I made a few adjustments to the secondary pull off spring, first two I had bog, the last one seems to have nailed it. I guess next I'll adjust the air fuel mixtures. So should I adjust the for max vacuum or for dwell? I've got both the dwell meter and vac tester so I could do either. I can't remember the name of it now but I know I measured the travel (?) through the top of the carb and I'm right at 2/32. If love to finally get this dialed in!
I think travel of the MCS (between rich and lean stop) is supposed to be more than 2/32, but can't remember. I'd have to do a crawl on thirdgen.org again to figure that one out.
