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Thread: How Fast Will A Quincy 6 Go ?

  1. #51
    Team Member Jeff Lytle's Avatar
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    Sweeeeeeet!

  2. #52
    Allen J. Lang
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    Will be looking forward to the videos. Nothing like the sound of a 6 banger looper at top end.

  3. #53
    Team Member Frank Volker's Avatar
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    I don't see any problem with 130+ with the right setup. If I were going for the last 4 or 5 mph, I'd run the old style elbows, move the water injection point about 1" from the flange, and run Gen II pipes with about 1" off. I'd also wrap the engine in some sort of aero-friendly cowl. If I got that far, I'd pull the inlet air from a common plenum fed by an air duct for at least some ram effect--which is a valid move at those higher speeds. But then, that's just me.

    Best of luck and enjoy the ride.

    Frank V.

  4. #54
    J-Dub J-Dub's Avatar
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    Default Elbows

    Why the early style elbows? We have plenty of the early style. What the difference between the two?

    J-Dub

  5. #55
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    perhaps the older elbow because of the shorter radius, places the reflection point in the megaphone closer to the exhaust port, narrowing the power band, but raising the RPM?

    I would like to know the thinking behind this myself, as I paid a lot of money to "update" a Quincy "C" to the later pipe elbow as is shown on the 6 in the picture, in either the late 60's or early 70's, probably the former, as the latest mod at that time for more HP/speed as touted by Christner.

  6. #56
    Team Member Frank Volker's Avatar
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    If I recall, there was a problem with some of the short radius elbows breaking in competition. Also, the Gen 3 flares were the best overall for the race course. The subject of this thread is "How Fast Will A Quincy 6 Go?" and is not about competition if I have interpreted the meaning properly. Moreover, I assume that J-Dub's addition to this discussion is about top-end speed and not a competition setup. So, with that in mind, my suggestions for J-Dub are based on the following:

    1. The short radius elbows and Gen 2 megaphones present a smaller projected (drag) area than the wide radius setup. This is particularly important with the top 2 cylinders, since drag at this point could result in sufficient torque at the transom to raise the bow. This is a surprise you don't need. A cowling around the engine would help, but a smaller projected area would help even more.

    2. Injecting water nearer the flange cools more straight section than injecting water at a location near the megaphone entrance--as is the case with the newer elbows/flares. This pseudo-lengthening of the straight inlet section would most likely pull more low-end HP and pull a bigger prop through the mid-RPM range faster.

    This is only my take on setting up a Quincy 6 and a somewhat loose answer to the "How Fast" question.

    Frank V.

  7. #57
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    Frank:

    Was I correct in my thinking regards shorter radius versus longer radius elbows putting the reflection point in the megaphones closer to the exhaust port?

    It makes sense that you would want a set up that would broaden out the power band for most of the motors that would be used primarily on closed course competition versus straight-a-way trials which were few and far between back then, and only at a few locations like Kaukauna, Alex, and a few locations in Florida.

  8. #58
    Team Member MN1's Avatar
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    Here's a photo of the Airmarine F Hydro at the Kakauna, WI Kilo runs.

    Mark N


  9. #59
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    That's an interesting idea Frank.

    I know that Dad and Larry tried the wide elbows with chambers for a while since Larry had success with the 2 cyl motors. However, on the 6 they couldn't resolve a lean condtion at sustained high rpm.

    As I remember, having a really good/strong ignition is mandatory and skidding rod bearings becomes a problem as your near the 10k rpm level

  10. #60
    Team Member Frank Volker's Avatar
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    Bill,
    I wasn't at QW during the change to the newer elbows. When I did my thesis exhaust work in '71, they were the std system. I'm guessing that the intent was to maintain centerline distance from exhaust port to megaphone with the newer elbows, since this is a most critical distance. I don't think anything but a very sophisticated CFD program could provide an answer to how the bend radius of the older vs newer elbow affects wave action, although I'm sure the boundary detachment at the inner radius was more severe with the older elbows.

    I'm sure that the older elbows would have an even higher failure rate with the big (Gen 3) flares, which were heavier than the older megaphones, but showed a definite HP improvement at upper mid-range to peak and over-peak HP. My biggest concern--tuning wise--with the newer elbows was that the water injection boss was near the megaphone end of the inlet pipe and the cast-in boss aimed the water directly downstream into the megaphone, seemingly bypassing a significant part of inlet pipe section altogether.

    Dean,
    A later exp chamber had a much fatter midsection. A mod'd version of this ended up on the Z engine. This probably pulled more mixture through the cylinders, possibly helping with the leaning condition. There were indications in some of the dyno tests that a constant injection of very small amount of water helped over the entire RPM range. It was very difficult to control, however. A sophisticated microprocessor-based control strategy could handle this, but that technology was about 10 years away. And there were not enough hours in the day.

    Frank V.

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