Thread: Building A looper Beast

  1. #461
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    Turn the fuel divider rail upside down so the initial fuel feed from tank will come in from the top down to the pumps, instead of bottom up. That might help guarantee equal distribution to pumps. Also, take a good look at the carbs. If you are using the diaphragm style carbs, check the pop off pressure. They might need to be about 9 or more psi before they pop off releasing pressure, but check the Tillotson recommendations for those models to be sure if not known. If the pumps are exceeding the pop off pressure, then put stronger fuel "needle/seat closing springs" in to get them right.

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    Have you considered a test prop?
    can use in the shop in a tank but also at the race site

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    Wouldn't fixed jets make more sense (or are adjustable jets more common on race engines)? Another (maybe worthless) suggestion when having fuel problems would be an electric fuel pump with a pressure regulator. This set up supplies reliable, consist fuel flow and pressure. I went this way after having 'weird' fuel flow problems and it cured them completely.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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    Quote Originally Posted by Fastjeff57 View Post
    Wouldn't fixed jets make more sense (or are adjustable jets more common on race engines)? Another (maybe worthless) suggestion when having fuel problems would be an electric fuel pump with a pressure regulator. This set up supplies reliable, consist fuel flow and pressure. I went this way after having 'weird' fuel flow problems and it cured them completely.

    Jeff
    adjustable makes for quick adjustment as its development engine
    more engines blown up by electric fuel pumps than 100% reliable pulse pumps IMHO ( saying that they dont work as well at big revs so you might need electric)

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    Don't agree with that statement at all.

    An electric pump PUSHES gas to the motor instead of SUCKING it there, as do vacuum pumps on outboards (and pressure is far more effective; it works with 5 to 7 psi pressure verses only a half pound of suction). A small air leak before the pump, or an unexpected restriction, and fuel flow is reduced, causing a lean out. In fact, many an OB has been damaged when the owner installed a water separator/ filter before the fuel pump, which didn't have enough suction to pull gas through when it was contaminated.

    Jeff

    PS: Virtually every serious race car uses an electric fuel pump, with the smallest automotive unit large enough for most outboards.
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  6. #466
    J-Dub J-Dub's Avatar
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    I had a very similar problem with my 60" Flathead. I was running a RAPAIR ignition box on my 66" deflector on gasoline, worked fine. So I took that entire ignition system off when I built my Looper. It wouldn't evn start! It would "Pop" & "Fart" and wear out starter ropes and guys pulling the rope, but nothing... I had a few "Old School" racers (Chuck Walters for example) telling me that I didn't have enough voltage to sustain enough spark with that amount of compression and fuel.
    I thought to myself "These guys just don't understand these newer RAPAIR box's, they work great! Me being nearly as stubborn as Steve Litzell, I was't giving up. After screwing with it for a while, I thought I would "Confirm" it wasn't the RAPAIR box. So I put a Mercury "Green" box on it with 24 volts like we used to do with the deflector six's on methanol.
    DAMNIT!!!! First pull! I have been running it that way ever since.
    This is a bit of a long way to go to question if the ADI ignition has the "Nuts" to ignite that much compression and fuel, combined with the duel plugs per cylinder on this Bad-A$$ engine...

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    J-Dub

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    You might be right. I have given that a lot of thought. The ADI system is a dual 3 cylinder system with a stator that has both high and low speed windings for each box. It could be dropping a box or a high speed winding. As you could see in the second time out of the pits it started to wind hard and then just dropped.

    We have run the six looper with the CDI distributor since the beginning with 24 volt as advised by Mercury engineering. We were told up to 30 volts possible. Just for sake of weight, we removed 1 battery and tried on 12 volt and it would not run clean. Had to reinstall the second battery.

    If I had had the time I expected at Hillsdale, I was prepared to change to single plug heads, diaphragm carbs and due some tuning. However!

    Dyno will be done in a couple of weeks and we will run as was at Hillsdale and resolve for the next attempt.

    As an additional note, the first 6 looper build was in the spring of 1966, pre CDI, and they tried all season to make run with the battery distributor that was the system used on the deflectors at the time. It would start but would not keep all 6 firing. The system did not have the secondary voltage to fire the fuel volume and pressure of the looper. The difference between the fuel flow for a deflector and the looper was an additional .060 fixed jet in the bowl tower.

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    J-Dub J-Dub's Avatar
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    Also, you may consider an MSD system. Rich Fuchslin runs two, 3-Channel boxes on his Stevens engine. And I think we ALL know how THAT runs! Also with the MSD you can run all 12 plugs by using two boxes. For example, on the MSD setups most people are using on their Konigs using two of the three channels. Therefore each of the two channels are split to run two cynders each as the top cyliders fire at the same time as well as the bottoms.
    So one magnet on the flywheel, six triggers on the stater delivering to two 6 channels (Two, three-channel boxes) that are split to run two plugs, then add a curve to the program for starting and such... Can anyone tell me what would be cooler than that???
    Besides you have CLEARLY demonstrated the fact you have 10X the talent necessary to accomplish the task... AND YOU ALREADY HAVE 12 COILS!
    B-Da Boom! B-Da Bing! Right?

    Add another $0.02
    J-Dub

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    you need a plug reading peak voltmeter to see what happens to the plug voltage as the load comes on
    Run it open circuit to see what reserve you have
    Great troubleshooting tool
    We had them in Australia in the late 70's but guy passed the business to these guys
    http://www.imrie.com.au/model_info/details_630.aspx

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    If the ignition was weak under compression, it wouldn't start as easily as it does and/or idle so good...but jumping fire, and shorting at higher RPMs has been my experience though, until I sealed the coil to plug wire connections with liquid tape or silicon. It could be ignition shorting under high RPM or acceleration somewhere within.

    As far as electric pumps, they are very good. What you need is a simple adjustable pressure regulator between the pump and carburetors. It would be just fine, and being just a concept engine and not a legal racer, this would be a go. It may solve your problems.

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