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'60 FI not producing enough horse power???

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  • George W.
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    • May 31, 2000
    • 544

    '60 FI not producing enough horse power???




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    05-28-2013, 12:30 PM #1
    1960fi
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    Testing FI unit air/fuel delivery

    Rebuilt 1960 Corvette 283 4 speed with FI not producing proper horsepower.
    (82HP on chassis dyno---would expect somewhere in the 220 range)

    Engine specs.:
    283, .060 over, complete rebuild, using flat top pistons.
    Duntov 097 solid cam--.012/.018 valve lash
    Initial timing 16 degrees/38 total
    14HG vacuum
    320 FI unit re-built/refurbished by known/respected Re-builder (not Jack Podell)

    Engine starts, runs, sounds terrific on both cold and hot starts.
    No hesitation, no surging at idle or during WOT.
    No pinging or detonation.
    No back-firing or any other obvious sounds/symptoms.

    Have inspected all fuel lines and there are no kinks or restrictions.

    Also have an additional fuel filter mounted below tank (will include photo).



    New exhaust system, no restricted flow.
    No heater valve at exhaust for this engine.
    Mechanical advance (not vacuum).

    A/F ratios 15.25:1 economy and 12.25:1 WOT

    My thoughts are that one or more of the following is occurring:

    1) High pressure pump not keeping up with demand at higher RPM (drive cable and dist gear are good)

    2) Restricted air flow during WOT (using K and N filter)

    3) Distributor/ignition system failure at WOT

    I have installed a glass bowl fuel filter housing in front of the fuel inlet of the FI unit and have observed this while under WOT (on dyno), and it stays full---I assume this eliminates any problem with fuel delivery restriction to the FI unit that could have been caused bt restricted fuel lines or faulty engine fuel pump.


    Questions:

    1)Is there a way to test the FI unit high pressure fuel pump?

    2) is there a way to test air flow through the unit?

    3) What can I do to test distributor/ignition system?

    Only other "malady" I have with this FI unit is with the fast idle screw--it is basically "non-responsive".

    The idle mixture screw is responsive, but not as "touchy" as I expect.

    Will add some photos when I can.

    Thanks for input,
    George
    geopar@gvtc.com
    210 748 4693

    Last edited by 1960fi; 05-28-2013 at 01:07 PM.
    05-28-2013, 12:47 PM #2
    65tripleblack
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    Quote:
    Originally Posted by 1960fi
    Rebuilt 1960 Corvette 283 4 speed with FI not producing proper horsepower.
    (82HP on chassis dyno---would expect somewhere in the 220 range)

    Engine specs.:
    283, .060 over, complete rebuild, using flat top pistons.
    Duntov 097 solid cam--.012/.018 valve lash
    Initial timing 16 degrees/38 total
    14HG vacuum
    320 FI unit re-built/refurbished by known/respected Re-builder (not Jack Podell)

    Engine starts, runs, sounds terrific on both cold and hot starts.
    No hesitation, no surging at idle or during WOT.
    No pinging or detonation.
    No back-firing or any other obvious sounds/symptoms.

    Have inspected all fuel lines and there are no kinks or restrictions. Also have an additional fuel filter mounted below tank (will include photo).

    New exhaust system, no restricted flow.
    No heater valve at exhaust for this engine.
    Mechanical advance (not vacuum).

    A/F ratios 15.5:1 economy and 12:1 WOT

    My thoughts are that one or more of the following is occurring:

    1) High pressure pump not keeping up with demand at higher RPM (drive cable and dist gear are good)

    2) Restricted air flow during WOT (using K and N filter)

    3) Distributor/ignition system failure at WOT

    I have installed a glass bowl fuel filter housing in front of the fuel inlet of the FI unit and have observed this while under WOT (on dyno), and it stays full---I assume this eliminates any problem with fuel delivery restriction to the FI unit that could have been caused bt restricted fuel lines or faulty engine fuel pump.


    Questions:

    1)Is there a way to test the FI unit high pressure fuel pump?

    2) is there a way to test air flow through the unit?

    3) What can I do to test distributor/ignition system?

    Only other "malady" I have with this FI unit is with the fast idle screw--it is basically "non-responsive".

    The idle mixture screw is responsive, but not as "touchy" as I expect.

    Will add some photos when I can.

    Thanks for input,
    George
    geopar@gvtc.com
    210 748 4693
    I'm very interested in hearing the responses that you get here, as I'd like to learn something about the Rochester system and its limitations.

    Based on your previous query, I'd first suggest that you might consider putting the car on another dyno for a single pull. If you can get that done for e reasonable price, it might point out an error with the first dynorun that you posted and establish a valid baseline for your tuning efforts.

    "A/F ratios 15.5:1 economy and 12:1 WOT"
    Unless the proper adjustment is supposed to lie outside of normal range, I can tell you that the leanest a/f ratio should be closer to 14.5-15:1 during cruise speed, and the richest should be around 12.5-13:1 at the engine's maximum torque speed which is at 4400 RPM. Ratio at maximum power speed should be slightly leaner than the ratio at maximum torque.

    Last edited by 65tripleblack; 05-28-2013 at 12:50 PM.
    05-28-2013, 12:56 PM #3
    1960fi
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    Edited A/F ratios in above post.
    Note: These numbers are apx. as the dyno reading was somewhat erratic.
    G

    Last edited by 1960fi; 05-28-2013 at 01:01 PM.
    05-28-2013, 01:18 PM #4
    Matt Gruber
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    why not a 0-60 mph test?
    or 5 or 10-60 street start, no burnout?

    Last edited by Matt Gruber; 05-28-2013 at 01:39 PM.
    05-28-2013, 01:58 PM #5
    1960fi
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    Quote:
    Originally Posted by Matt Gruber
    why not a 0-60 mph test?
    or 5 or 10-60 street start, no burnout?
    I could do that, (in a way I have).

    I have another '60 that has the same engine (running a carb at this time), same specs, and it "hauls". Pulls 6,500 RPM all day.

    So I can tell a big difference without using a stop watch.
    G.
    05-28-2013, 02:21 PM #6
    ZR WON
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    It's easy for me to type this, but I rarely follow this advice :

    Try for the simplest thing first. When reading through your combination, the first thing that stuck out is the K&N Filter... I had a VERY similar problem to what you described with my ZR-1 (newer car, I understand, but the motor is still an air pump). The only difference is I was actually running the quarter mile vs. checking power with a dyno.

    Best ET when the car was stock was 12.89 at just under 112. I ported the plenum/injector housings (may not mean much to you, but it should have added around 50-60 rear wheel horsepower, this has been documented). After going back to the track (similar conditions), the best time was 12.84@113; I was absolutely disgusted. All that work and the car was .05 quicker and 1mph faster.

    I started to go through my mind the various things that could potentially be causing this issue. It of course went to the 'worse case scenario.' Did I reinstall something incorrectly, was something else wrong with the motor? It then dawned on me that in addition to all the port work, I changed to a K&N filter. I also remembered reading if you over oil the filter, it severely restricts the amount of air allowed into the engine, creating exactly the symptom I was (and you are currently) experiencing. Long story short, I removed the air filter for the next run and ran 12.3@117 (and subsequent runs were in the 118 and change). There was the 50-60rwhp I was missing.

    I would never expect anyone to necessarily believe this, but I can tell you that I will never use a K&N Filter again based on this experience. To be clear, the decision is NOT because I feel K&N is an inferior filter, it's solely because I so rarely drive the car these days, I can change the conventional filters every year without worry or high expense.

    Brian A.
    90 ZR-1
    12.09@118
    01 Z06
    not quite stock

    Last edited by ZR WON; 05-28-2013 at 05:25 PM.
    05-28-2013, 02:21 PM #7
    MikeM
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    Quote:
    Originally Posted by 1960fi

    A/F ratios 15.25:1 economy and 12.25:1 WOT

    My thoughts are that one or more of the following is occurring:

    1) High pressure pump not keeping up with demand at higher RPM (drive cable and dist gear are good)

    2) Restricted air flow during WOT (using K and N filter)




    Questions:

    1)Is there a way to test the FI unit high pressure fuel pump?

    2) is there a way to test air flow through the unit?

    The idle mixture screw is responsive, but not as "touchy" as I expect.

    Thanks for input,
    George
    geopar@gvtc.com
    210 748 4693
    IF:

    You verified the A/F @ 15+ @ WOT at 6000 or so rpm, It would seem your high perssure pump is okay. It would also seem that you have no air inlet restriction (but see the post above).

    The mixture screw should be very responsive. That would bother me but I don't know what to tell you.

    Your engine won't start to make a lot of power until approaching 3000 so if you're still stuck at 4000 or less, I just don't know what to tell you.

    Last edited by MikeM; 05-28-2013 at 02:32 PM.
    05-28-2013, 02:27 PM #8
    Matt Gruber
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    it sure helps to put a # on it.
    i had a fiero 92hp 0-60 11 sec.

    then u may find several causes and can see improvements.
    #1 - throttle not opening all the way, but i'm sure u checked that.
    #2. check WOT vacuum 5k+. should be under 2".
    #3. look at plugs; all nice tan? nothing black?

    Last edited by Matt Gruber; 05-28-2013 at 03:02 PM.
    05-28-2013, 02:45 PM #9
    jim lockwood
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    George,

    To keep you from wasting time exploring things which are not problems, let me offer some info about air/fuel ratios.

    If you are running straight gasoline, an economy ratio of 15.5:1 and a power ratio of 12.5:1 are what you want. These are the design points for Rochester FI.

    On the other hand, if you are running E10, you want an economy ratio of about 14.9:1 and a power ratio of about 12.0:1

    Now having written that, let me point out that some equipment, notably that from Innovate Motorsports, measure a property called Lambda, not air/fuel ratio. Internal to the equipment, Lambda is multiplied by a conversion factor (default is 14.7) to produce the displayed air/fuel ratio.

    What does this mean?

    It means that regardless of what kind of fuel you use, if you run 5% lean (15.5:1 on gasoline, 14.9:1 on E10), the indicated AFR will be 15.5:1.


    One other point.... if your engine sees 12:1 (or 12.5:1) at all engine speeds during a WOT run, the high pressure pump is flowing as it should. That's not to say it doesn't have worn bushings or pitted gears or excessive clearances. It might. But it's flowing enough fuel.


    I don't know why your engine doesn't make enough power so I don't have anything else to add.

    Jim
    05-28-2013, 03:14 PM #10
    1960fi
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    Quote:
    Originally Posted by ZR WON
    It's easy for me to type this, but I rarely follow this advice :

    Try for the simplest thing first. When reading through your combination, the first thing that stuck out is the K&N Filter... I had a VERY similar problem to what you described with my ZR-1 (newer car, I understand, but the motor is still an air pump). The only difference is I was actually running the quarter mile vs. checking power with a dyno.

    Best ET when the car was stock was 12.89 at just under 112. I ported the plenum/injector housings (may not mean much to you, but it should have added around 50-60 rear wheel horsepower, this has been documented). After going back to the track (similar conditions), the best time was 12.84@113; I was absolutely disgusted; all that work at the car was .05 quicker and 1mph faster.

    I started to go through my mind the various things that could potentially be causing this issue. It of course went to the 'worse case scenario.' Did I reinstall something incorrectly, was something else wrong with the motor? It then dawned on me that in addition to all the port work, I changed to a K&N filter. I also remembered reading if you over oil the filter, it severely restricts the amount of air allowed into the engine, creating exactly the symptom I was (and you are currently) experiencing. Long story short, I removed the air filter for the next run and ran 12.3@117 (and subsequent runs were in the 118 and change). There was the 50-60rwhp I was missing.

    I would never expect anyone to necessarily believe this, but I can tell you that I will never use a K&N Filter again based on this experience. To be clear, the decision is NOT because I feel K&N is an inferior filter, it's solely because I so rarely drive the car these days, I can change the conventional filters every year without worry or high expense.

    Brian A.
    90 ZR-1
    12.09@118
    01 Z06
    not quite stock
    Won't hurt to try with another filter.
    Thanks,
    G
    05-28-2013, 03:19 PM #11
    1960fi
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    Quote:
    Originally Posted by jim lockwood
    George,

    To keep you from wasting time exploring things which are not problems, let me offer some info about air/fuel ratios.

    If you are running straight gasoline, an economy ratio of 15.5:1 and a power ratio of 12.5:1 are what you want. These are the design points for Rochester FI.

    On the other hand, if you are running E10, you want an economy ratio of about 14.9:1 and a power ratio of about 12.0:1

    Now having written that, let me point out that some equipment, notably that from Innovate Motorsports, measure a property called Lambda, not air/fuel ratio. Internal to the equipment, Lambda is multiplied by a conversion factor (default is 14.7) to produce the displayed air/fuel ratio.

    What does this mean?

    It means that regardless of what kind of fuel you use, if you run 5% lean (15.5:1 on gasoline, 14.9:1 on E10), the indicated AFR will be 15.5:1.


    One other point.... if your engine sees 12:1 (or 12.5:1) at all engine speeds during a WOT run, the high pressure pump is flowing as it should. That's not to say it doesn't have worn bushings or pitted gears or excessive clearances. It might. But it's flowing enough fuel.


    I don't know why your engine doesn't make enough power so I don't have anything else to add.

    Jim
    Hi Jim,
    I was hoping you would reply.
    You've answered my question concerning the FI high pressure pump---thank you.

    I'm running 100 aviation fuel.

    Any comment on the K and N air filter?

    Any comment on the non-responsive idle adjustment?

    Thanks again,
    George
    05-28-2013, 07:00 PM #12
    jim lockwood
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    Quote:
    Originally Posted by 1960fi
    Any comment on the K and N air filter?
    No. I've never used one.

    Quote:
    Any comment on the non-responsive idle adjustment?

    In your first post you said the fast idle screw was non-responsive. If you mean the screw which contacts the fast idle cam, then as long as it contacts the cam, there has to be some effect. There has to be.

    The response you are getting to turning the Idle Fuel screw sounds about right.


    Based on what I've read so far, I don't think there is anything wrong with your FI unit.

    Jim
    05-28-2013, 07:31 PM #13
    Chuck Gongloff
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    Quote:
    Originally Posted by 1960fi

    Rebuilt 1960 Corvette 283 4 speed with FI not producing proper horsepower.
    (82HP on chassis dyno---would expect somewhere in the 220 range)

    Engine specs.:
    283, .060 over, complete rebuild, using flat top pistons.
    What was the theoretical the compression ratio?

    Have you checked each cylinder?

    Sounds like the FI unit is performing well. I'd do a compression test on each cylinder....

    Chuck
    05-28-2013, 08:08 PM #14
    1960fi
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    Cranking compression (plugs removed, starter speed only, and without throttle open) is150 in all cylinders (sorry that I did not provide this info in original post).
    G
    05-28-2013, 08:13 PM #15
    1960fi
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    Quote:
    Originally Posted by jim lockwood
    No. I've never used one.




    In your first post you said the fast idle screw was non-responsive. If you mean the screw which contacts the fast idle cam, then as long as it contacts the cam, there has to be some effect. There has to be.

    The response you are getting to turning the Idle Fuel screw sounds about right.


    Based on what I've read so far, I don't think there is anything wrong with your FI unit.

    Jim
    My error,
    Fast idle screw (on choke cam) working.

    Idle speed screw is non responsive.
    05-28-2013, 08:45 PM #16
    MikeM
    CF Senior Member

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    Quote:
    Originally Posted by 1960fi
    Hi Jim,
    I was hoping you would reply.

    George



  • Jerry G.
    Extremely Frequent Poster
    • April 1, 1985
    • 1022

    #2
    Re: '60 FI not producing enough horse power???

    If I were going to hazard a guess, to loose that much power would take more that one cylinder not contributing. I'd check plugs and wires. Jerry

    Comment

    • Don H.
      Extremely Frequent Poster
      • December 1, 1981
      • 1487

      #3
      Re: '60 FI not producing enough horse power???

      I have been drag racing a high HP '60 for over 30 years. I gave up trying to read this thread with all the "copy & paste" from another site. Sorry, probably just me. Don H.

      Comment

      • Robert S.
        Frequent User
        • May 31, 1988
        • 81

        #4
        Re: '60 FI not producing enough horse power???

        Have someone else operate the gas pedal and see how far the throttle really opens. It is possible for carpet to limit "full" throttle to about 60 percent of full throttle. This is really hard to diagnose with only one person. Don't ask me how I know.

        Comment

        • John D.
          Extremely Frequent Poster
          • December 1, 1979
          • 5507

          #5
          Re: '60 FI not producing enough horse power???

          Actually George it's not just Don. I can't follow it either. John

          Comment

          • George W.
            Very Frequent User
            • May 31, 2000
            • 544

            #6
            Re: '60 FI not producing enough horse power???

            Tried to "clean-up this thread---Did not work---working on it.
            In the mean time--please read first post on post #1 describing problem, engine specs, and questions.

            Additional information:
            1) plugs good, wiring correct
            2) full WOT achieved with pedal (no interference)
            3) running 100 aviation fuel
            Thanks,
            G
            Last edited by George W.; May 31, 2013, 08:18 AM.

            Comment

            • Dick W.
              Former NCRS Director Region IV
              • June 30, 1985
              • 10483

              #7
              Re: '60 FI not producing enough horse power???

              Cleaned the thread per George's request
              Dick Whittington

              Comment

              • Mike F.
                Expired
                • April 25, 2011
                • 668

                #8
                Re: '60 FI not producing enough horse power???

                Are you sure the problem isn't with the dyno or dyno operator? Which type of dyno was it? What gear did you do the dyno runs in (4th gear/1.1)? How many runs did you make?

                82hp at the rear wheels equates to approx. 94hp net/104hp gross. Hard to believe that if your engine sounds somewhat "normal" when running that it could only put out 82hp/104hp. Your car would feel like an 84 Plymouth Horizon if it only had 84hp.

                FYI - My recent L46 rebuild made 341hp/387tq on an engine dyno and 244hp/305tq on a chassis dyno (Dynojet).
                Last edited by Mike F.; May 31, 2013, 01:56 PM.

                Comment

                • William C.
                  NCRS Past President
                  • May 31, 1975
                  • 6037

                  #9
                  Re: '60 FI not producing enough horse power???

                  OK, two questions:

                  #1-Have you verified the timing mark on the harmonic balancer is actually in sync with the "O" hash on the timing tab? Outer ring on the balancer can slip.

                  #2-Have you verified that the distriburor centrifugal advance is working properly to provide the proper spec at the factory specified RPM (or before...)
                  Bill Clupper #618

                  Comment

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