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attacking a monojet

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  • main jet #2

    current jet: .079 = 2.0066
    gm used a #80 on a 1.6 liter. Rethinking main jet on chevette needle. the slob is gone now..the delay that puffed black smoke is a trick to think it was plenty of fuel. just the opposite..

    next: .081 = 2.0574 mm

    I am guesing this might be .082 for an ea82...not sure. They never explained their engine designations. I will try two jet sizes bigger.

    another hint was no bellow, until needle removed from jet. Even rich, the #79 is in the low 20s mpg (no needle in the middle).

    that was my only hint..the bellow of demaning air like I know rochesters do...it is hardly existent right now. I must be hypermiling.

    full CAI has a hellacious sound on the all steel can (I am giggling) when this is correct.
    with bypass in place, dynamics of a bigger top end can be thought of.
    Last edited by Barry Donovan; April 20, 2012, 11:49 AM.
    Previously boxer3main
    the death rate and fairy tales cannot kill the nature left behind.

    Comment


    • Originally posted by boxer3main View Post
      current jet: .079 = 2.0066
      the delay that puffed black smoke is a trick to think it was plenty of fuel. just the opposite..
      I've seen this too! lean misfire but thought it was overly rich because of a puff of black smoke. Kept taking out fuel, misfire gets worse. WHAT THE HELL!

      I think the smoke is the residual fuel, unburnt due to "not enough fuel" that then burns when the engine relights. Not sure but, your description sounds like what I am talking about.

      Still following this thread,
      -Scott
      www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

      Comment


      • Originally posted by dieselgeek View Post
        I've seen this too! lean misfire but thought it was overly rich because of a puff of black smoke. Kept taking out fuel, misfire gets worse. WHAT THE HELL!

        I think the smoke is the residual fuel, unburnt due to "not enough fuel" that then burns when the engine relights. Not sure but, your description sounds like what I am talking about.

        Still following this thread,
        -Scott
        I did get tricked no doubt. easy to do.

        I was looking up solex for beetles...
        1600cc to 1776cc with the same carb has 7% increase in jetting.

        this applied to the current setup would put me at a #85 (2.15mm) holley. I guess I am way off...well, if a smidgen tenth a millimeter is way off.

        another measurement was using millimeters instead of inches, finding 7%.
        this puts me at a 2.17mm
        ..odd.
        another trick was the air bleed. the chevette had a little one..but venturi must have been crammed, hence it must have worked. I need to stay with what gm gave the 250cfm to be sure I get a bleed at all...the barrell is huge in comparison.

        oem plays safe ..so maybe compromise, old gurus numbers, and my own..

        #82
        2.0828
        in the guys article..he did mention the hazard of air cool. as liquid cool, 3 jets smaller is plenty in boundaries. air cooled needs rich. it is surviving a #79 now.

        it could be more than a conicidence. "ea82" is engine label. hard telling.
        Last edited by Barry Donovan; April 20, 2012, 02:52 PM.
        Previously boxer3main
        the death rate and fairy tales cannot kill the nature left behind.

        Comment


        • more plating

          I will be using the original needle (custom ground) with the next jet...I gave it a cathode/anode clean, now using the eagle to get some plating across. makng an acid is easy. simple as slat water and lysol 4n1 lime stain remover (mineral agitator)

          The main jet needle with a brass eagle.
          I am opting for my custom needle to go with the next main jet #82. The needle in use now seems rather custom by rochester to go with a long #80, a raised jet. The needle getting plated is the original..but seems to be foolishly copper. I grinded this down to what I feel the curve is. without braggin.. I now I am right before even using it. the number87 is on this needle.. I seriously believe that is the main jets max stamped right on the needle. Close enough for me.The water turns green, plating of some kind is happening. (brass has either yellow or green when it becomes a solution).
          So this makes everything custom. my own idle jet, float and seat from a chevette, and my favorite is the return line. I may be adding a brass liner to that, found also in the chevette carb..seems an exact fit for inside the throttle cable return as a reducer. this way, any old fuel line can be hooked up.
          Last edited by Barry Donovan; April 20, 2012, 06:05 PM.
          Previously boxer3main
          the death rate and fairy tales cannot kill the nature left behind.

          Comment


          • custom main jet

            the number 80 chrome jet is so close to what my goal is.. I just let it have some ingenuity. I liked the thought of engineers intentions on a four cyl with a monojet. I just simply went bigger. Worth some effort.

            the remains of a steel rivet had some divets on the back end.. I thought to check it against the number 80 jet. sure enough..a slight bit bigger. I stuck it in the drill gun and it won the jet. I then polished the reaming with the awl, much harder than the jet, by hand. Verifying a gain was easy. the awls point sticking out distance from the hole compared to before and after, and of course against the #79 jet next to it. if the chrome jet is now not a #82, close enough.
            I may be a be able to use original needle..but each rochester gets its own angle on the needle. the 250cfm in the car has an angle not perpendicular to tall jet like the chevtte carb this came from. it will still give rochesters purpose to use the old needle I custom ground. stabilizer, antikick. it will simply have more elbow room.
            will try this install soon.

            plus a quarter of 1mm is a #81, half a mm is an 82..very precise stuff they got there.
            I am certain to be closer to 82.
            Last edited by Barry Donovan; April 20, 2012, 08:03 PM.
            Previously boxer3main
            the death rate and fairy tales cannot kill the nature left behind.

            Comment


            • long 82 and needle

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              I am getting quicker at this..all the screws on the float bowl cover, pluck the float out of the way without losing needle for float on the little clip. The custom needle is much smoother than photo.. I gave it some plating and thorough cleaning to verify plating even worked. I noticed some perfect ridges, very slight..as if to be someones nominal throttle settings in th past on longer trips.
              dropped this in, did not like the power valve and how many adjustments it has had..but is staying put. I may get another rochester just for power valve. The chevette one does not fit.
              Started easier dead cold. off idle to partial throttle was improving before even purging into final seat. this is going to the best run of custom so far.

              back to the feel of a real throttle curve, I let the tinging valves work their way to quiet, this means bothering neighbors revving..getting the purge of fresh air bubble out. I am playing with 30mpg after all.

              this is the best answer yet. The other needle had a fat end, hardly any taper at all. I think I found the lean problem at speed or long hills. the other needle could not let it have anymore. This needle in photo, as throttle is given, fattens the mix. the reutrn line helps, as fuel gets colder using it..but that is more for purging and let float have an easier life. It also helps getting changes to take place.Now back to a hard set dynamical feed, I love it.




              so stepping away from oem build..
              • the four cyl proves to need the raised jet,
              • a real taper on the needle,
              • the small float bowl seat, and float..
              • return line was the scariest chore. could wreck a bowl, and that means bad carb.
              And as for the jet numbering.. I found per barrel of rochester, 78 to 80, no matter where it is at, seems to be the most common number ever. I bet each barrel revolves around a given engineering limit, and then they just add more barrels to go bigger engine.

              If I had known it was that simple...
              Last edited by Barry Donovan; April 21, 2012, 08:45 AM.
              Previously boxer3main
              the death rate and fairy tales cannot kill the nature left behind.

              Comment


              • float bowl vent baffle


                found this for a holley float bowl vent baffle. I found the monojet is sitting flush, wide open..anything with gravity can fall in..so I found some piping, a bit reduced in size..but so is the fuel I am using, and doubted it until the lockdown for the plenum bar screwed tightly against, and also gave it a little bit of silicone that ignores gas. I have it taking a right turn, peeking over in the airstream of barrel. this also adds an object above air bleed openings..a protector of sorts.

                oddly enough, this is the only carb I have seen with no extra pipe taking vent into airstream of barrel..and sitting flush open like that. this is a correct thing to do.

                this chore here should end a long list of not so little things..even though they are little.
                I looked over the hitachi close..as tiny as everything was, it stayed robust enough for a 25 year run. I voluntarily took it off the engine as I outran the fuel air with big cams. I can admit I went guru with basic knowledge to keep things happening..not exactly rocket science to be a maintainer.
                I never even primed it changing a fuel pump..that was an indicator that the pump is a volume based more than pressure, ignoring 3 psi was a good idea. Return line is very clever.

                in this post with the barrel side of bowl vent..the hitachi had a complete shutoff, electrically controlled. I looked over the spare monojet wondering how I could machine something like it in to work...
                I still may come up with something.

                being as this is a true needle and seat carb now..the hitachi was not.. the extras are proving to be unnecessary..except for the electrical connection on a resistor.
                the vent shut seems to be the cold start keeper. Could sit for weeks..and bam..right to life in a high idle. the monojet is not so happy about that. it might be now..It is too soon to say yet.

                I did learn the prime trick..turn key on, starter..no start..wait for pump and don't keep on starter or pump fuel. that is where this one might have to stay. alright by me.

                for the first time in what seems to be a year..
                looking at 4 inches total rain in a couple of days.

                all it takes is a barometric pressure change to drain a carb to looking like a dead oxide log.
                a reason for painting, a reason for alot of things. the fuel on the return will move on its own..car on or not.
                Last edited by Barry Donovan; April 21, 2012, 04:32 PM.
                Previously boxer3main
                the death rate and fairy tales cannot kill the nature left behind.

                Comment


                • gas light on

                  I wanted to see if an infection was in the tank..a down low heavy one. gas light on, started up well, went to gas station and put in one gallon.
                  no strange odors..so the valve going tinny was a lean or strange crud..could be silicone gas. it did quiet down to silent.

                  the void all the boxers I have driven is right up to 2000 rpm...idle air good.
                  A promising sound today, a bark an ea81 with one cam would make during casual take off..no cough. with all the timing work I put into it (gates hard belts on an ea82 was not possible as oem), I was glad to hear that void filled in. I have heard it fake this before..the fake is no power to go with the bark. today was different. I am happy about that. The engine is funny in that as power and air fuel speed up in the curve, the engine gets strangely quiet .. that is self balanced in action. the only noise is air fuel if I let it.

                  will attempt to get a different camera. No fan club for this one.. this one is for truth.

                  the monojet is only little on a big engine.

                  a daydream for this setup once correct was a 2 speed powerglide...and take this n/a pipsqueak to a drag strip.
                  I did spot the chevette front suspension. .. that is a long distance away, these outrageous extras.
                  Last edited by Barry Donovan; April 21, 2012, 08:06 PM.
                  Previously boxer3main
                  the death rate and fairy tales cannot kill the nature left behind.

                  Comment


                  • summary (final)
                    • #80 long jet, gently reamed (close to a #82)
                    • custom needle, full taper (I may have simply taken out an oem retarder- hard telling)
                    • chevette nitrophyl float (made for this type of monojet)
                    • chevette float needle and seat, modified
                    • float bowl and cover painted carbon black pigment (purified carbon is pigment- simply rustoleum bumper paint)
                    • 2.2 ohm choke, also chevette (ohms to match 1.8 liter per engineers thinking)
                    • 56ohm connection on back bolt (resemble modern gadget connection, keep carb as cathode, anti-pig)
                    • bimetal relief filled in (this was used on 250 cubic inch as a relief)
                    • full CAI, custom 16ga steel boot ring
                    • full return line, .035 inch restricted
                    • fuel filter removed at carb
                    • custom thin base gasket to intake (ensures vacuum ports on the base)
                    • choke spring (helps it close partially upon shutdown)
                    • idle solenoid removed (crazy function- 1970s monojet)
                    • bowl vent for inside barrel is now a pipe with a right angle, reduced slightly and into airstream (idea from other carburetors)
                    • custom throttle hookup
                    • maximized adjustment on power valve (flush to bowl)
                    • the capped screw for stoich adjustment , drilled and turned until 1.5 turns out from closed
                    • custom brass idle air mix screw (looks like chevettes 4cyl, but made with proper thread to work in big monojet)
                    • threaded external fuel bowl vent connection (reduced slightly)
                    • new choke pull off, restricted to open much slower
                    • progressive vaccum port in perfect use with ignition.
                    • lastly..custom gasket out of my favorite plastic folgers coffee jug (next post)
                    I think this is all I did..

                    will add to it if I forgot.
                    open to suggestions too.
                    as there is no shutoff for venting, I check valved with a pcv valve, and it worked. I found some 1970s emission stuff for fords, I could put that on a vacuum control valve, or they really make an "air check valve". does not seem to be necessary at this time.

                    old monojet is modern. The main jet is fancier than even the most modern...among other things on the list.
                    Last edited by Barry Donovan; April 22, 2012, 11:18 AM.
                    Previously boxer3main
                    the death rate and fairy tales cannot kill the nature left behind.

                    Comment


                    • custom gasket

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                      I caught onto my coffee jugs strangely tough materials, being under the sink, toluene, my car paints, bolts with stuff on them,batteries..the plastic junk never died.

                      I then went onto trying one as a thermostat gasket, just the lid, as it is softer. sure enough, held right up. I stuck some in toluene and let it sit to see what would happen. Nothing. did not even get soft.
                      the monojets materials are as prehistoric as cork rubber. I don't get mad..all my engines have been in this torture.


                      I'll make my own. if this ever proves to be silly, the coolant jugs or oil jugs are also sure wins.

                      note the barrel cutout is oversized to keep the dreaded cfm thief from squishing into it...dangling, robbing the air of the extra 1/100th of a horsepower.

                      Click image for larger version

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                      here is old gasket.
                      since installed the new one..there is one trimming I did too much of (yellow circle), in a useless spot anyway, the hole does nothing..in fact it is a lip that sticks out. I did have to have the progressive spot (green circle), I left extra. the monojet in top photo is the chevette, not like the 250ci one exactly, but enough to make a gasket. I also trimmed back (blue square) some of the gasket hanging over float. this may promote more vent..
                      this did nothing to notice. although idle seems a thumpier. I did cure a leak after all..it was at the air bleeders (two tiny holes in the middle of gasket in top photo)
                      cold start still stubborn.

                      when I first got this, the gasket stunk real bad. the new gasket is smelling neutral.
                      I can only see one potential problem fixed..and that was around needle power valve. it drops out the bottom of carb..potential vacuum leak on float bowl side. the new gasket gets that a little better.

                      valves still smacking around..have been through this, although rarely. change oil, hot day..pounce on the throttle once and awhile.

                      I also found the engine hates ATF. Rather than put in its third power steering track, I found some sealer called at205...one could laugh, but I think its the cold start problem, and valve noise. it hits the pipes, vapors of atf flying..and it stinks like I have never smelled before. shut down, gets cooled..and there is the slop needing a full warm engine to get over it..
                      Last edited by Barry Donovan; April 22, 2012, 04:32 PM.
                      Previously boxer3main
                      the death rate and fairy tales cannot kill the nature left behind.

                      Comment


                      • new problem

                        I forgot to take this thing highway to see if the bellow is back .this tells me it is rich enough.

                        it is indeed there. the let down is instant off..the long jet can't play games.

                        a new problem is in the cold. it did the opposite of warm up faster..the draft is even colder. I can pop thru carb if laying it on too fast.

                        I refuse to go all plenum under the hood like the old days..

                        a heat riser needed...
                        even the I-6 had a warm up time for this carb. all plenum under the hood to roast it in minutes.

                        the new gasket seems to be a cold one as well, no odors after shudown. As if the old gasket was some weird catalyzer.

                        valve noise is a lean condition coming back around to richer and colder. springs will take some time. this boxer has done this more times than nothing I know survives.


                        anyone play with CAI and carb..the heat riser subject? I need a simply clever idea.

                        I have a resistor on the fuel, and a partial draft under hood...not enough.

                        Click image for larger version

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                        I was thinking of how the plenums worked. large area above carb, electrocutable, sloppy chamber of deadness. it is to keep the venturi happy..slow feed.
                        Above is a wheel bearing race on top of the float bowl cover upside down. it is nearly the same size as the barrel. I will put this in the intake tube, wedged ..this may fake a chamber like a plenum has, by sizing up the demand before it gets to carb...and leaving a slower space of the larger air duct that follows the race...I ponder it is over a foot after this race is wedged in to be the slow down.

                        I am avoiding heat riser as that sucks on city sewage, hondas an evos...and whatever else.
                        Last edited by Barry Donovan; April 22, 2012, 08:34 PM.
                        Previously boxer3main
                        the death rate and fairy tales cannot kill the nature left behind.

                        Comment


                        • tuning the plenum

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                          no vacuum valves, no thermal vacuum switch, nothing that will break to useless after finding it never worked. I want nature.
                          this is wheel bearing race with pc fan grate over it to screw it to plenum end. another freak fit..it is the exact same size. the race is heavy and the final size for barrel..larger by a small amount. the grate is to stop free flow. all stainless.

                          will it work? don't know yet.


                          overthunk? no.

                          a test ride. car will be sitting for a couple of weeks. would love to just pounce a 1000 miles into it. still stubborn cold starts. the cold cough did subside a bit. A good rain storm..could drive all day in it.
                          seems a world of crap in the oil side now..pcv may be releasing the monster that hung onto the carb. taking plenum apart to put in my gadget was no brain robbing odors.

                          stainless in the presence of air duct scare away many things. enzyme related. the little four banger is flowing too much to care about that anymore..but I still think of it.
                          Last edited by Barry Donovan; April 23, 2012, 07:35 AM.
                          Previously boxer3main
                          the death rate and fairy tales cannot kill the nature left behind.

                          Comment


                          • summary in video

                            there is not much else to conquer. stuff not mentioned was not important.

                            I may tinker with an engine oilpan heater, stick it on the air box. little stuff. The custom plenum stainless piece is to promote pcv inlet with carb gasses..else it won't get anything but arctica...10% humidity.
                            been there with more than this car. engineers know hawaii more than america. that is coincidental to..
                            oh nevermind.


                            first vid:
                            february 8 2012, the intake stuff. first looks.
                            I have to use music that does not get me into trouble. making my own loops is usually a safe bet.



                            last vid Apr 22, 2012



                            the driving clips or cold starts etc..showing errors along the way, as if to be immortally forever stuck there. those vids are deleted. people are stupid.


                            I was reading my local paper..internet is doubled for everyone in my locale. Here I thought the registry cleaner was giving me a faster net. thanks to "docsis 3.0"

                            anyway..my vids are actually wide screen 10mbit, panasonic ( good stuff), for several years I have been squashing them into a blur due to an insanely slow upload.
                            finding old settings.. I was even uploading sound at 256kbit in the past. I'll be back to that shortly.


                            this air/fuel stuff, seeming to be way overthunk to you?

                            changing plugs to hot the other day I noticed the intake valve open at the plug hole...between rocker ratio, solid lift, and an injection cam that has lobes looking like an egg..
                            the lift is over half inch. in the v8 world, well we know what this is don't we. to have a smooth idle..I must have done something right with a monojet and mismatched subaru parts.

                            manufacture ships easiest for themselves and a warranty. This is just another car going to a real runtime..who cares what power numbers are.

                            the fuel air subject gets much nerdier than me and this boxer.
                            Last edited by Barry Donovan; April 23, 2012, 01:58 PM.
                            Previously boxer3main
                            the death rate and fairy tales cannot kill the nature left behind.

                            Comment


                            • for other monojets


                              the red is where it is not the same as mine, all else is good enough for explaining.
                              the accelerator pump shares main well (the last real revision of common sense), those are the monojets to go for. I know 1976 onward is a sure bet. else..adjustments don’t even matter. it will be a single digit low teens mpg hog. There is an obsolete versions to everything.


                              adjustable part throttle metering orifice. Yet another description of the extra hole near main jet. A real desire to leave that far open gets a performer..but yet again makes it a hog after vacuums are happy, engine warm. I found keeping it tight and make the carb earn the path will get a real stoich like modern (ie: 1.8 liters should be 30 something mpg). My own is 1.5 turns out..and may tighten it by end of summer. No monojet has clean paths. Make it earn them to be real. (example: The 4.1 L should be middle twenties mpg – do not stop letting it cough until it is there.)

                              a last trick for that hole, is sticking a pipe in the same size (press in some copper or whatever) and raising it up if you know the carb is clean. on my own, the jet is raised.. so I may use the little pipe that came with the chevtte and raise to .25 off the float bowl floor, and trim from there. I need the summers long day ride to finalize these little things. I treat a carb like welding chores...as long as it is 56F at a low temp at night. that needs middle of summer here.


                              all else is simply clever. for real tight stoichs, little engine..raising the jet, return line, and little float (old brass for monojet if you can’t find a chevette version) is a real runtime.

                              for the sharing main well accelerator pump..I had a friend who analyzed my 1974 chevelle, and he got excited about that...funny, at the time, I called him a nerd. that one move double and triples mileage..makes the main well gain pressure to seat a jets path to running tight. That is where I learned about the part throttle adjustement getting uncapped, and screwed right in to 1.5 turns and letting it have no more. (my chevelle was middle twenties mpg)


                              I'd really scrap the other monojets unless preservation of exact oem build for your classics year is the goal.
                              on multi carb gurus, they can take those pumps right out, even the metering needle. there is ways to hack old to new. the real line drawn is seeing if it has a stainless barrel..no stainless? its a scrapper.
                              Last edited by Barry Donovan; April 24, 2012, 07:47 AM.
                              Previously boxer3main
                              the death rate and fairy tales cannot kill the nature left behind.

                              Comment


                              • gasket check (coffee lid)

                                the coffee jug and lid is made of HDPE. High-density polyethylene.
                                I guess I used the highest grade gasket available at big big cost.


                                they make gas tanks for cars out of the same stuff. any hardening is hydrogen leaving. wherever it is squashed between bowl cover and float bowl is where gasket stays soft. it digs into the little ridges monojet uses. never moves. kept a memory as I poked and peeled. no stickiness.

                                also..it proved the old gasket, a tar like covering..that one was very very bad, it may have even been toxic. almost holding my breath taking bowl cover off, expecting that horrifying brain stabbing odor..there was none. the new gasket also kept it worlds cooler. An inert you just know is there content.
                                if this gasket proves to be too thin , or not strong enough, other plastics include any oil jug, or even coolant. all reusable. pluck the top off and play with jets all I want.

                                I wanted to see how the coffee lid gasket did, and if idle air hole got filled in by squish.. i am going for very tight, as the gasket is a plastic trait.

                                the gasket swelled up (I don't mean the material, I mean it moved the gasket upward like a balloon) and hardened around float bowl needle, fuel pressure/moving is much bigger than I thought. wow. return line reason infinite..

                                all else is perfection. I trimmed a little more at idle hole.

                                an odd thng to take note of (they all do this, guaranteed)

                                I installed main jet and needle, they weren't exactly aligned. today it is perfection. did it all on its own overnight...the jet moved to the needle. not the needle to the jet. I bet its a power valve electrode gain and loss.

                                ready to go. engine sounds bad.. but I got fuel air...

                                ..and engine may not be done of course, big changes can rumble any engine.

                                I am so very curious about the 115mph marker and beyond. the spongy four cyl feel has a climb. the boxer is like that.
                                Last edited by Barry Donovan; April 24, 2012, 08:26 PM.
                                Previously boxer3main
                                the death rate and fairy tales cannot kill the nature left behind.

                                Comment

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