Re: Jetting& Altitude
[Re: pjc360]
#1644665
07/10/14 12:31 AM
07/10/14 12:31 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I'd not stray from the basic "one change at a time" rule. I'd get the vent taken care of & check if the float level should be at the bottom of the hole or where you have it halfway up. Wallace racing has excellent pics of plugs for jetting/heat range or an innovate LM1 is the best/pro way to get it spot on
live every 24 hour block of time like it's your last day on earth
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Re: Jetting& Altitude
[Re: pjc360]
#1644669
07/10/14 07:13 AM
07/10/14 07:13 AM
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Joined: Oct 2003
Posts: 21,345 Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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I've heard guys on here say that RPM with no load will cause the carb to go lean, thus red headers. That said, before I knew anything about AFRs, rich/lean, etc. When I took my car out to Colorado, I followed the chart that Edelbrock provided with the carb, on what jets/rods to use at various elevations. The car ran and drove fine the 2 years I had it out there. ALthough, it didn't have any power, but what NA motor does at 7,000 feet ACTUAL elevation? I'd bet the DA on most days was up near 10-12k
**Photobucket sucks**
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Re: Jetting& Altitude
[Re: 70Cuda383]
#1644670
07/10/14 07:58 AM
07/10/14 07:58 AM
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Joined: Aug 2007
Posts: 1,531 AZ
Mike P
pro stock
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pro stock
Joined: Aug 2007
Posts: 1,531
AZ
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One jet size per 2000 Feet has been my experience. I live at 4500 feet and usually make an annual trip to see family that live at 200 Feet. To tune the car back to "normal" would take 2 jet sizes and taking about 2 degrees out of the timing.
1957 Plymouth (Hemi, Dual Quads, A833 4 Speed 9 1/4 w 4.10) Sold 1937 Dodge Pickup (Hemi, 6X2 intake, 46RH, Dana 60 w 4.56) Sold 1968 Plymouth Valiant 2dr sedan (354 HEMI, 46RH w/4.30 gears) under construction
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Re: Jetting& Altitude
[Re: Mike P]
#1644671
07/10/14 08:38 AM
07/10/14 08:38 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Yes too lean will make em glow red as will way too rich & it's burning in the ex but for it to go away when you pumped it tells you which one you are dealing with. I'm assuming there is no vac leak that is skewing this and the float levels are correct. I'd k.i.s.s. richen those jets ASAP before something fries.
live every 24 hour block of time like it's your last day on earth
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Re: Jetting& Altitude
[Re: pjc360]
#1644672
07/10/14 09:03 AM
07/10/14 09:03 AM
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Joined: Jan 2003
Posts: 5,446 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,446
Indiana
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It appears from what you have written that you are lean from idle to 2500rpms which would point to the idle/transfer circuit, not the main jetting. The idle and transfer consist of the Idle Feed Resisters, Idle Air Bleeds, and the metering screws. You noted that your metering screws are 1-1/4 turns out which sounds like a lot for a QF carb. If you richened up your IFR's, you might be able to get the metering screws back down under 1 turn (Z at QF suggests under one turn out each.)
My guess is that your .025 IFR's are too lean and you are making up for that by turning your metering screws outward to 1-1/4 turns. Once you are off idle, the metering screw setting still affect the A/F during the transition into the main circtuit. But, above idle, the IFR's and the IAB's are also contributing to your A/F ratio. Since you richened it up by adding 3-4 pump shots, that is telling you that you are lean and could be the real reason for the red headers. I would suggest going back up to the .031 IFR's to richen up your transition circuit.
(REF NOTES ONLY: On my Super Street QF carb, my mains start in around 2500-2700rpms. In four years, I have never had my metering screws in or out more or less than 1/2 to 7/8 turn outward each. I currently run .033IFR's and .050 front and .060 rear IAB's and I get 14.0-14.2 at 45mph which is 2400rpms but I am at a lower elevation than you. I looked back at my tuning notes and I found that when I first started tuning with an A/F meter, I was running with .028 IFR's and my 1700rpm cruise was WAY LEAN at 17.0 and my 2500rpm cruise was still lean at 15.6. [E10 fuel]. QF also suggests floats set at 1/2 up the glass. My SS also came with 68 main jets and I am now running 67's. I have tried 58-67 main jets with many other changes while testing A/F ratio's. The 67's give me mid 13 A/F readings at cruising speeds at 55-65mph [2700-3300rpms] which is my current goal) and they give me the most throttle response when my PV is open [along with .078 PVCR's])
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Jetting& Altitude
[Re: pjc360]
#1644675
07/10/14 09:17 PM
07/10/14 09:17 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I'm assuming your timing is in the ballpark at the particular fast idle RPM that makes em glow red. This might be too simple but I'd think it could be way too lean at (fast) idle (the idle circuit) but the transition/mains are in the normal range & it richens up enough to straighten out.
live every 24 hour block of time like it's your last day on earth
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Re: Jetting& Altitude
[Re: pjc360]
#1644677
07/10/14 09:53 PM
07/10/14 09:53 PM
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Joined: Jan 2003
Posts: 5,446 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,446
Indiana
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""When I was running .031 idle feed restrictors my plugs were fouling at idle it was so rich.""
Then you compensate with the metering screws. If I remember correctly, you have an auto. The next time you have the engine running and if you can take it for a short drive to get it up to temp, then put the car in D (with emergency brake or someone behind the wheel) and tune the metering screws evenly until you get the best vacuum reading at the idle rpm of your choosing. The goal is you have the highest vacuum reading at your chosen rpm and the metering screws are all outward even. This vacuum number becomes your goal after any future idle adjustments. Always meet this number or get higher at the same rpms. You will need to readjust the metering screws every time you change the IFR's or the IAB's. I would still suggest that you retry the 031's and then readjust your metering screws for the highest vacuum reading. Then if your metering screws are still outward more than 1 full turn, then drop down (richen up IAB's).005 sizes (or what ever size you have) and then readjust your metering screws once again. You are super lean at high idle (apx 1200-1500rpms or so?) and this is the IFR's/IAB's or the metering screws. Since your metering screws are out 1-1/4 turns, I think your IFR's are tooooooo small. You need to fix the glowing headers first and then lean out your idle in D. Fix the leaking baffle that you wrote about too. If you don't want to go larger on your existing .025 IFR's, then put some small wire down inside of your IAB's to test. This will make the IAB's smaller/richer but I am not sure it will be enough.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Jetting& Altitude
[Re: pjc360]
#1644679
07/10/14 10:13 PM
07/10/14 10:13 PM
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Joined: Jan 2003
Posts: 5,446 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,446
Indiana
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""there was no symptom of a lean condition while driving it. Only when it was sitting in park. Why is that?"" When you are sitting in P at high idle, you are idling on the transition circuit. When you are tooling around town, you have help from the front pump circuit to help on acceleration until your mains start in. The pump circuit is a designed-in "bandaid" to help cover up any lean spikes during the transition into the mains. It sounds like your current pump setup (squirters/pump cam) is doing its job along with the .028/64 main setup. Since you are using 64 jets and .028" MAB's (fairly rich which starts the main circuit sooner than a .033" for reference), this may be allowing the main circuit (jets and MAB's) to start fairly early and the main circuit may be tuned fine. This might be why you do not have any known issues while cruising. Please concentrate on richening the IFR's and the IAB's.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Jetting& Altitude
[Re: pjc360]
#1644681
07/10/14 11:33 PM
07/10/14 11:33 PM
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Joined: Jan 2003
Posts: 5,446 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,446
Indiana
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They are not only a tuning tool but a teaching tool as well! You can have a gauge/O2 sensor kit for apx $190.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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