Air:Fuel Help. Cannot Get it Rich

Small Block Mopar Engine

  1. pishta

    pishta I know I'm right....

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    you can spray water too and find the leak, just set it at a low idle for max vacuum and spray water in a stream onto the check points and listen for a drop in RPM's. Hey, itll clean the motor too. The power valve is supposed to richen 8 jets on activation. Is it working? Low vacuum is supposed to open it up as the high vacuum sucks it shut against a light spring.
     
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    • Sterling

      Sterling Well-Known Member

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      Had a lean problem with a 318 I built years ago, took me a long time to find out the intake manifold wasn't sealing underneath, in the valley. Got a smoke machine now to help find vacuum leaks
       
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      • dilweed

        dilweed Well-Known Member

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        You'll have to pardon my ignorance, but I've never heard of alcoholized fuel, or if I have, i don't know anything about it.
        I've been fighting this for a few track events, and have gone through a couple different jugs of fuel. I believe a couple different jug fillings maybe from the same station, but perhaps not spread out long enough that it would be a different load from the station.
         
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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        Up here we call it gasohol. They mix ethyl alcohol into the gas to increase the octane rating of supposedly chitgas so the oil companies can sell more gallons of gas from the same amount of crude; and the dollars keep rolling in for them while the MPGs of the newer cars go up; those greedy bums.
        So anyway you gotta watch the pumps; if there is alcohol in the gas, the sticker will be on the pump, saying something like "may contain up to (x) percent alcohol", x being 10 or 15. You may know it as oxygenated fuel, cuz they like to hide stuff.
        E85 requires almost twice as much fuel to make the same power, and when you jam it thru too-small jets it ain't but half big enough. E10 and E15 are not that critical but you still need to upjet. That happened to me one time on a roadtrip; I couldn't even cruise on the primary jets, I had to stop on the shoulder of the interstate and upjet. And the first guess wasn't enough,nor the second.
         
        Last edited: Oct 9, 2018
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        • dilweed

          dilweed Well-Known Member

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          I..assume.. the power valve is working since it started running lean with the old one in, and the new one in. It was remained lean with new pv in, and jetted up 8 on primary and secondary.
          I'm a bit particular on spraying all over the engine bay, so thanks for the water reminder!
           
        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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          It helps if you flip the fanbelt off during the diagnostics.
           
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          • dilweed

            dilweed Well-Known Member

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            oh yes. we have those stickers! Oxygenated.
            Hmm, I learn something everyday. thanks for this info. perhaps I need another trip for a fresh gas.
             
          • pishta

            pishta I know I'm right....

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            They should put those stickers on nitromethane too......

            Have you taken a vacuum reading yet; Are you low? bolt a lift plate up on top a carb gasket (or a piece of sheet metal to seal carb pad) and pull the rocker shafts to close all the valves. plug all but one vacuum locations and chuck it to some compressed air. give it a shot and listen with a stethescope for any hissing or bubbles from a light soapy mix in a squirt bottle. A sprayed leak will cause bubbles. We 'flash test' airtight splice cases with same procedure and can find any pressure leak on the seams down to 2 psi. should find any vacuum leak with this method too, but ones under the intake will be audible only.
             
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            • 70aarcuda

              70aarcuda Master Hoader of SBM FABO Gold Member

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              E85 only requires about 25 to 30 percent more fuel to make the same power as gasoline....on the track it makes more power then gasoline....Our getting in our carbs are about 10 jets sizes larger. The supply line is a AN8 with a Chinese black holley pump. Our here in the desert with temps over 100 degrees....the intake manifold on the engine while it is running is very very cool.....
               
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              • dilweed

                dilweed Well-Known Member

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                Hmm, now that's a good idea.
                I did a leak down a while back and all was good. I did a vacuum reading even further back, and embarrassingly, I cannot remember the reading, but there were three of us standing there, and we all said "good there". Another reading is in order.
                 
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                • mbaird

                  mbaird mbaird FABO Gold Member

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                  I may have missed this but how do you know its running lean ? A/F gauge ? Checking plugs ? Is it popping ?

                  Could be bad sensor or gauge...

                  I once chased a lean issue and found it to be a kinked line at the tank. Must have done it while changing gears.
                   
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                  • dilweed

                    dilweed Well-Known Member

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                    1/4 mile ET and MPH fell off about 3 tenths and 3-4mph, checked plugs and all of them went from rich to white lean. It's open headers at the track and I do believe I've heard popping once (while doing burnout at higher RPM). It hasn't just "layed-over" while making a pass, but you can feel a difference.
                    I do have an o2 gauge and new sending unit, but I do not trust the reading. It's telling me 10.5:1 at the top end of the track, and that's just not possible with how the plugs look. It's a new sending unit as my first one stopped sending a signal (because I think i was running rich for so long), so i'm not sure why it's giving me such a rich reading.
                     
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                    • j par

                      j par Well-hung Member

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                      Another dumb question but at this point we can't cross anything out. Did you recalibrate after you put the new sensor in?
                       
                    • dilweed

                      dilweed Well-Known Member

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                      I did not recalibrate anything. I believe the o2 sensor is just a plug and play. It's an Autometer wideband.
                      I haven't had to really do much calibration for the carb over the years. Small increments from out of the box. Actually been working a bit over the years to try and lean this up a bit. It's always been on the rich side.
                       
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                      • j par

                        j par Well-hung Member

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                        I have an Innovative wideband O2 sensor and you definitely have to recalibrate it if you're going to put a new sensor on it? There should be instructions online or something?
                         
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                        • Tooljunkie

                          Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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                          I quit using flammables to find vacuum leaks a long time ago. Vapours found an exhaust manifold leak and lit up the engine bay. Water works just as well.
                          Nothing serious happened,but not something i would want to push my luck with.
                           
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                          • fishy68

                            fishy68 Tyr Fryr's Inc. FABO Gold Member

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                            Unless I missed it I don't see anything about the fuel pump. Sounds like a weak fuel pump not keeping up to me
                             
                          • j par

                            j par Well-hung Member

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                            Yes I think you missed it LOL he did talk about checking fuel pressure and such.
                             
                          • fishy68

                            fishy68 Tyr Fryr's Inc. FABO Gold Member

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                            Ok, thanks. I wonder if he verified volume? You can have pressure but low volume
                             
                          • dilweed

                            dilweed Well-Known Member

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                            Hi, yes, new pump, and also verified flow with a stopwatch and a fuel jug. I believe I was right on the money. Regulated at 6psi, I think it flowed 5 gallons in 1:36.
                             
                          • j par

                            j par Well-hung Member

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                            could you do me a favor and go ahead and actually read his post because I believe he went through that too?
                            That way you don't need to keep kind of shooting from the hip.
                             
                          • nm9stheham

                            nm9stheham Well-Known Member

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                            Good point... the OP has changed pumps, and checked pressure, but that pressure check is likely at idle and that does not say anything whatsover about that pressure being maintained at the top end under max flow conditions.. And, the OP checked open pump flow into a container, BUT, that says nothing about flow into back pressure; pumps with poorly functioning check valves with have their flow drop radically or to nothing when back pressure is applied.

                            So, while those are good checks to do, they are not 100% conclusive checks that the pump & fuel system are delivering fuel properly at max flow conditions.

                            The easiest way to know is the rig up a fuel pressure gauge that can be observed when running hard. Just be safe when doing this.

                            OP, I see you put in a new pump of adequate specifications. Did you change the regulator? And while the free flow test says the pickup is good, any way the cell pickup, or any foam blocks, are moving around and getting masked under acceleration?
                             
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                            • j par

                              j par Well-hung Member

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                              Let's be careful here because it seems the carriage in the horse are both running neck-and-neck? We still haven't verified that the O2 sensor has been calibrated? We haven't put everything back together and drove a little bit to see if the plugs are doing anything different from any changes that are made or have been made? I guess what I'm getting at is let's make sure we're not making too many changes before we don't know what's going on.
                               
                            • dilweed

                              dilweed Well-Known Member

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                              I looked at the product info on mine (Autometer 3379) and it says no "free air calibration necessary", so perhaps I'm good on this. I've got it located at the collector of the header as well. Weird.
                               
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                              • j par

                                j par Well-hung Member

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                                You know I'd like to say I have something to bang mine off to test it? I mean all I can do is really calibrate it and hope that it's working? And of course you drag race so you know watching the plugs is the biggest thing. The two should go hand-in-hand.
                                I don't like changing a part before I verified that it's the problem. I find this costly.
                                 
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