Author Topic: Velocity Stack Vs. Scoop  (Read 7194 times)

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Offline wolfie

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Re: Velocity Stack Vs. Scoop
« Reply #10 on: October 14, 2011, 09:01:19 PM »
I think we need to get Steve to start building Scoops! We can have David's nephew put logos on it! I'd pay some good money for one of those!!!

Offline 78_Tahiti

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Re: Velocity Stack Vs. Scoop
« Reply #11 on: October 14, 2011, 10:34:19 PM »
I think we need to get Steve to start building Scoops! We can have David's nephew put logos on it! I'd pay some good money for one of those!!!
I do make my own scoops!  :sign0068: I don't make enough money to own one otherwise.  :redface: I make mine out of stainless though. I can weld that. If I was to find a nice newer inverter TIG Welder (like a miller or Lincoln) for really cheap, and I mean really cheap! I could start building stuff with aluminum too! I've been working on a build recipe for a stroked 460 engine. If it comes together, I'll prolly have Rich (Santana Upholstry) Laser Etch something creative on the scoop!  :zdrool:
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Offline wolfie

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Re: Velocity Stack Vs. Scoop
« Reply #12 on: October 14, 2011, 11:51:01 PM »
If you start building and selling, I'm first in line with the for a stainless!!!  :biggrin:
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Offline TIMINATOR

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Re: Velocity Stack Vs. Scoop
« Reply #13 on: November 11, 2011, 12:31:08 AM »
A velocity stack actually hurts the airflow. Many scoops do too. Carbs actually draw air from slightly below their flange area, so a scoop with a flat bottom at least 2" around the flange, or better yet one that drops about 15 degrees from horizontal is best. When I wrote for Hotboat, I did an article on making your jetboat faster, and I covered all of that and more. I had info on Dominator carbs too. The 1050 on my Daytona now flows 1310 on my Superflow bench, all without altering the boosters or venturis. There is more there, but I've been busy, I'll get to it before the summer. The new motor has been in the boat since March and I still don't even know how fast it is yet! I'm looking to get about 1400 cfm without touching the venturis or boosters, that way it still takes the stock jets and the economy is great! LOTS of tricks to this! The cheapest and best "scoop" is a 10" stainless dog bowl mounted upsidedown on a 1/4" all thread rod. Then for even better flow, make a 1 1/2" ring around the carb flange that drops down at a 15 degree angle. I set these up on the carb on the flowbench, and have found that you can vary the gap between the bowl and ring to set the best airflow for your size carb. P.S. removing the choke horn only works for 800 or 850 carbs, the smaller ones never see any gains at all. I could write an entire article on this, but I don't know who publishes a Jetboat magazine anymore. We sell the Chineese Holley HP 920 series carbs for $459.95, hand assembled and blueprinted. The only issues are the quality control, I.E. burrs on reamed holes, etc. These work great on anything from a stock 455 Olds to a 700 HP BBChevy, and best of all, the jetting seem to stay very close to stock for these extremes. That shows that the airbleeds and emulsion tube sizes are spot-on. You are better off assembling them and inspecting them yourself if you know what you are doing. DON'T buy one assembled, you'll only end up checking them after they don't perform perfectly out of the box. The standard jetboat scoop drops the cfm of an 850 or 920 by about 70 cfm! and for dual carbs, it is even worse! TIMINATOR
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Offline David

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Re: Velocity Stack Vs. Scoop
« Reply #14 on: November 11, 2011, 06:35:20 AM »
Great info!!! Would love to see pics of these as well...
What does a piece like this do to my 850dp?
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Offline 77GT

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Re: Velocity Stack Vs. Scoop
« Reply #15 on: November 11, 2011, 06:43:28 AM »
A velocity stack actually hurts the airflow. Many scoops do too. Carbs actually draw air from slightly below their flange area, so a scoop with a flat bottom at least 2" around the flange, or better yet one that drops about 15 degrees from horizontal is best. When I wrote for Hotboat, I did an article on making your jetboat faster, and I covered all of that and more. I had info on Dominator carbs too. The 1050 on my Daytona now flows 1310 on my Superflow bench, all without altering the boosters or venturis. There is more there, but I've been busy, I'll get to it before the summer. The new motor has been in the boat since March and I still don't even know how fast it is yet! I'm looking to get about 1400 cfm without touching the venturis or boosters, that way it still takes the stock jets and the economy is great! LOTS of tricks to this! The cheapest and best "scoop" is a 10" stainless dog bowl mounted upsidedown on a 1/4" all thread rod. Then for even better flow, make a 1 1/2" ring around the carb flange that drops down at a 15 degree angle. I set these up on the carb on the flowbench, and have found that you can vary the gap between the bowl and ring to set the best airflow for your size carb. P.S. removing the choke horn only works for 800 or 850 carbs, the smaller ones never see any gains at all. I could write an entire article on this, but I don't know who publishes a Jetboat magazine anymore. We sell the Chineese Holley HP 920 series carbs for $459.95, hand assembled and blueprinted. The only issues are the quality control, I.E. burrs on reamed holes, etc. These work great on anything from a stock 455 Olds to a 700 HP BBChevy, and best of all, the jetting seem to stay very close to stock for these extremes. That shows that the airbleeds and emulsion tube sizes are spot-on. You are better off assembling them and inspecting them yourself if you know what you are doing. DON'T buy one assembled, you'll only end up checking them after they don't perform perfectly out of the box. The standard jetboat scoop drops the cfm of an 850 or 920 by about 70 cfm! and for dual carbs, it is even worse! TIMINATOR

What you are describing sounds like the old style air cleaner assemblys that used the round filters.  The bottom section had a hump and the top was dished.  Something old is new again.
WASP aka:77GT

Offline H20MOFO

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Re: Velocity Stack Vs. Scoop
« Reply #16 on: November 11, 2011, 07:51:29 AM »
FWIW I run a velocity stack just cause its simple...I keep a bucket and a tie down in the boat in case I run into rain or big wind and water. I am convinced my boat would be at the bottom of powell right now with out that bucket. I have run with and with out the stack and he makes zero noticeable difference on my ride. Usually the scoop debate is run it forward or backward. I have heard more than 1 person claim it runs best backward....kinda the same principle as the cowl hood on a chevy.

Offline Kona Kandi

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Re: Velocity Stack Vs. Scoop
« Reply #17 on: November 11, 2011, 08:31:54 AM »
I have heard that theory before, and tested it myself. It does work, but doesn't look all that cool. I decided to stick with my stack, so I had it polished up so it is nice and pretty :cheers:


It doesn't really  matter whether you win or lose...
as long as you look good doing it.

Offline newtojets

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Re: Velocity Stack Vs. Scoop
« Reply #18 on: November 11, 2011, 10:10:46 AM »
I always liked the look of the scoop!  not to menchin, stuff tends to fall into stacks, especially with kids around  :furious3:

Offline wolfie

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Re: Velocity Stack Vs. Scoop
« Reply #19 on: November 11, 2011, 10:17:59 AM »
I always liked the look of the scoop!  not to menchin, stuff tends to fall into stacks, especially with kids around  :furious3:

I forgot what forum I read it on, but there was a story of a guy who took his boat out. Forgive me if I leave out anything or get it wrong but the jest of it all is humorous. The guy couldn't get it up to speed at all. Got mad, loaded it on the trailer and when he was buttoning everything up, found that one of the kids sand shovel had blown up and into the scoop blocking the airflow.
Another story was a guy who was firing the engine up for the first time. It wouldn't fire. Went through everything; was getting gas, spark, everything!! Gave it a shot of Kwickstart and it fired but out of the corner of his eye he saw something blow out the back of the boat. It was one of the rags that his buddy stuffed into the intake manifold before they put the carb on. I guess they forgot to take it out and when it did light off the ether, it sucked it into the cylinder and out the exhaust.
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