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  • Fuel System: fuel to air ratio for r-2

    I am trying to do things right this time.
    My 59ht with an r-I (#1984) is punched out .040 ,I put it together with erb 9.8 to 1 dished pistons and thin head gaskets ,then I added a r-2 set up from Lionel ,Mallory dist. and carb from tbo,ported the heads, and used the high output pulley combo from erb.Making about 5.5 lbs. of boost.
    It ran great for about two years and then I notice a small drop in wheel spin shifting to second ,
    Couldn't figure out why!
    A friend suggested a leakdown test, I said fine once he explained what it was ,so we did it.
    cylinder number one 98% Great
    cylinder two thur eight Make the radiator erupt ,Ok bad head gaskets, pulled it apart, luckily no glazed cylinders. Now I want to make sure this doesn't happen again. So I put the engine back to-gether with thick head gaskets and low compression heads with r-3 valves.
    My friend who is very knowledgeable about boosted engines ,Gave me a crash coarse in FUEL TO AIR RATIO Numbers and explained I needed A wide band oxygen sensor to check my AFR under boost .Well this we did and sure enough I was running 13.5 to 14.1 under boost which is very lean and dangerous for the engine. He told me I needed to find out what the ideal number should be or close to ideal. Phil Harris is the only one I could find so far, that had a idea .He says and my friend agrees it should be about 12.0 to12.5 approx. . great I now have a number to shoot for .
    So I bought jets and metering rods from edelbrock.
    I have 401 primary jets with 7547 metering rods and 389 secondary jets. I am going to try 398 for secondary jets and see what the numbers are .
    Anybody else familiar with this situation.
    1959 HARDTOP R2 4speed
    1960 conv R2 auto
    SDC member since 1972
    http://i237.photobucket.com/albums/ff21/59r2/DSC01514-3.jpg

  • #2
    What "situation" ?

    All internal combustion engines run best at "about" 14.7 .
    BUT crusing vs light power, vs heavy power, vs full throttle (and off throttle !) all require different values for the "best" stoichiometric ratios.
    Just crusing, around 14.5 will get you around just fine, no danger. But from there on, just like the extra squirt you get from the accelerator pump, you need more fuel for a controlled period of time...then it can disapate back down some.

    Just do some reading on on air-fuel ratio, you'll find it in the internet. There's a TON of information out there on how to tune your engine with an oxygen sensor.
    And remember, NO engine requires the exact same amount of fuel at the same time...otherwise, all race vehicles would run the same speeds..and have the same power !
    You need to experiment on where you need fuel and where it needs to be a little lighter. I'm talking small percentages here, not huge amounts different. Also depends on the car weight, gear ratios, transmission, etc., etc.
    Nuthin new, the same informations been around for many a year. It's just easier to get it right now-a days.

    Mike

    P.s. - Your best bet is to find a shop with a chassis dyno, and go there to more quickly and accuratly find the "best" tuneup for the current condition of the engine.

    Comment


    • #3
      I run the .098 primarys, .095 secondarys, The 70-47 rods, and Orange springs. No problems. Perhaps you just need to stiffen up the springs, and richen up the secondarys (for sure).
      All this is close to sea level .
      Last edited by bezhawk; 10-14-2014, 07:25 PM.
      Bez Auto Alchemy
      573-318-8948
      http://bezautoalchemy.com


      "Don't believe every internet quote" Abe Lincoln

      Comment


      • #4
        I am running .101 in the mains with 70-47 rods. I use .095 jets in the secondaries. At cruise speeds I get readings of 13.3 but at full boost I drop to 11.9 or 12.0

        Remember leaded fuel ruins an oxygen sensor in short order so be careful when using "track" fuel

        Peter Sant

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        • #5
          The other component interacting here is the distributor initial advance, centrifugal advance, total and rate. The A/F which produces the best power and least chance of detonation is affected directly by the timing.

          As previously suggested, the way to know what your engine wants for both timing and A/F is a session on a chassis dyno. Otherwise, verify your distributor has the R2 curve.

          jack vines
          PackardV8

          Comment


          • #6
            Bez,Peter I will try the .095 secondary jets .If no good , then the 70-47 rods Then the 98 secondary
            Jack I set the timing to r2 specs at full advance , static seems okay ,starts easy and f/a ratio is excellent till boost which is at about 4300 rpm
            Chassis dyno would be the way to go but I'll have to locate one
            Thank you I will let you know
            Joe
            1959 HARDTOP R2 4speed
            1960 conv R2 auto
            SDC member since 1972
            http://i237.photobucket.com/albums/ff21/59r2/DSC01514-3.jpg

            Comment


            • #7
              Go nowhere near stoiciometric with a carbuerated, blown engine. Carbs cannot respond like EFI to keep you out of detonation. That's why you see guys like Peter, KoolR2 successfully running fast with A/F in the 11's and 12's with the secondaries open and cruising in the low 13's.

              Adjustment to A/F ratio on AFB's is done via the jets, metering rods and the springs on the metering rods on the primaries and by the jets on the secondaries. How the primary interacts with the secondaries is adjusted by the linkage between the primary and secondary throttle shafts and the air door on the secondaries. It's easy to work on the primaries by themselves by locking out the secondaries with the latch where the choke engagement stops the secondaries from tipping in on the driver's side of the carb. Get the primaries working right then go on to the secondaries. You'll probably note that the A/F starts to get sketchy as the RPM's start to get higher so limit primary only tuning to under 2000rpm. This gives you a chance to get the primary jets, metering rods and springs right without the secondaries giving you false enrichment data.

              Since you normally don't make boost holding the throttle to just the primaries, you can jet them leaner. Adjust your secondaries to start coming in when your boost starts to come up. The richer secondaries blend in more and more fuel as they open. The air valves only drop in as much air through the secondaries as the engine is pulling. It's not as precise as EFI, but you can adjust the AFB's much better than some other carbs as the primaries only change the primary, the idle only changes the idle and the secondaries only adjust the secondary fuel inputs.

              Set your secondary engagement by bending the linkage to tip in the secondaries as needed. Lighten the counterbalances on the secondary air valve if you don't get the A/F to drop as quickly as needed when the boost comes in. Driveability when on the primaries and throttle response is usually the springs on the metering rods and stiffening them brings in more fuel sooner as you open the throttle. This is a somewhat simplified explaination. Hopefully Ted can provide a better explanation.

              One final note. The Mallory distributors are not set up with the R2 advance curve. You'll have to get an advance curve kit for it. Do a search, it's here somewhere. If not, try the racing site. It makes a big difference and setting the R1 curve to R2 specs is not the same.
              Last edited by jlmccuan; 10-14-2014, 08:07 AM.
              Jim
              Often in error, never in doubt
              http://rabidsnailracing.blogspot.com/

              ____1966 Avanti II RQA 0088_______________1963 Avanti R2 63R3152____________http://rabidsnailracing.blogspot.com/

              Comment


              • #8
                Thank you Jim very good info, I have the kit for the distributor and will search for the posting on how to do it
                1959 HARDTOP R2 4speed
                1960 conv R2 auto
                SDC member since 1972
                http://i237.photobucket.com/albums/ff21/59r2/DSC01514-3.jpg

                Comment


                • #9
                  I'd use an advance timing light and a tach to map out the centrifugal curve I have.
                  When you had the heads off did you take some nice close up pix of all 8 pistons?

                  I'd be concerned about any indication of erosion of the edge of the piston, expecting to find it in the regions furthest from the sparkplug.
                  This picture shows a pretty severe case, but provides an idea what detonation damage looks like.

                  Comment


                  • #10
                    It's ok to run close to 14:1 @ cruise. During high RPM and full boost, closer to mid 12 to low 13's is very good. It's also better to keep the engine intake temps on the cool side that helps keep detonation at bay too. (oil temp needs to be at least 160 before you romp on it.) Running rich makes the charge density higher because of the cooling effect of a rich mixture. That's why running a rich mixture makes a little more power, even though you are not able to burn it. Stoichiometric is the ideal chemical air to fuel mixture that uses all the oxygen in the combustion process. It is not a fixed number as it varies with air density (altitude, humidity and temperature) They all affect how well the fuel burns, and how completly.
                    Bez Auto Alchemy
                    573-318-8948
                    http://bezautoalchemy.com


                    "Don't believe every internet quote" Abe Lincoln

                    Comment


                    • #11
                      59r2 you didnt mention the fuel pump type and wether or not you have a boost reference line from carb to fuel pump. at 5.5 lbs boost you are running close to the fuel pumps pressure limit. once you pass that point lean out occurs and bad things happen quick, and you cant hear diddly squat! my turbocharged '62 lark hardtop w/4spd once hit 18+ lbs momentatily one day. managed to "squeeze" out head gaskets in same place on all 8 holes. i had overdriven an r/2 pump and carter street strip "booster pump". after the fact i realized my fuel filter with"vent line" had bled off to much precious fuel pressure. I'm installing a pressure guage so i can watch fuel pressure and "boost". Aint it fun! Doofus

                      Comment


                      • #12
                        Dan --the pistons were inn perfect shape no sign on the edges or any loss of metal they are still clean showing all machined lines
                        Bez-- I have the manifold cross-over blocked off with Jeff's stainless plates
                        Doofus- I have the line from the s/c to the fuel pump and no bleed off
                        Joe
                        1959 HARDTOP R2 4speed
                        1960 conv R2 auto
                        SDC member since 1972
                        http://i237.photobucket.com/albums/ff21/59r2/DSC01514-3.jpg

                        Comment


                        • #13
                          Joe, At the strip I set the timing at 33.5 degrees advance at 2000rpm with the vacuum line disconnected. I am running a Pertronix Ignitor Two in a Delco window distributor. At the track I use 112 octane fuel.
                          Peter Sant

                          Comment


                          • #14
                            I'm not advocating for anyone to shoot for this but on the Tomato I have one of the FAST air/fuel meters and under full power with 110 racing gas, it shows about 10.6. I thought this was way to rich but when I lean it down the times and speed suffer. ?? So I leave it at the 10.6 ratio.

                            I don't know if my meter is off, if the sensor is in the wrong place (about eight inches down from the exhaust manifold in the exhaust pipe) or what. The primary side of the carb is stock jets and rods but the secondary side is .098", up .009" form the stock .089".

                            The exhaust temps read about 1400 degrees at the end of a quarter mile run. It runs with 34 degrees total timing (without any vacuum advance) which is hotter than I think it should be, especially as rich as it is. But again, maybe the meter is off or the sensor not placed where it should be? Tail pipes are black and sooty.

                            One thing for sure, you want to be too rich rather than too lean.

                            Ted

                            Comment


                            • #15
                              That's another reason in favor of running a Rochester Quadrajet. They have secondary metering rods and are infinitely adjustable. Even the rate in which they come in, and also the secondary air valve is adjustable.
                              If one was running fuel injection, and a blower you would have to do some fancy programming to get the computer to run rich enough.
                              Bez Auto Alchemy
                              573-318-8948
                              http://bezautoalchemy.com


                              "Don't believe every internet quote" Abe Lincoln

                              Comment

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