Author Topic: Velocity Stack Vs. Scoop  (Read 7190 times)

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Offline TIMINATOR

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Re: Velocity Stack Vs. Scoop
« Reply #51 on: November 23, 2011, 07:18:27 AM »
The "ram air" pressure at 100 mph is about .1 (yes thats one tenth of a psi), tha carb/ motor can easily pull near an entire pound of suction behind the carb element in a scoop. As far as adding the holes to depressure the carb, the holes are a good idea, but the explanation is wrong. I have a flowbench, radar gun, gps, and a low pressure air (Magnahelic) gauge. I document what everything does, then analyze, and only then make changes. Then I record the differences if any , and then go back to the way everything was to recreate the original performance to make sure nothing else threw off my test. I have raced for over 40 years and take going fast seriously, I don't guess, and I don't post about anything that I haven't tried.  Having a half of an inch or even an inch above the element is not nearly enough, because you are forcing the air to go into a small area above the element, and then turn 90 degrees down, then another 90 degrees back into the air element, then 90 degrees down into the carb. Air has weight, mass and inertia, and you are fighting all of that. When you have that much restriction you are changing the effective jetting of the carb. Due to the change of density altitude of the air with temprature and humidity, you can't effectively make up for that with jetting. I run an expensive stainless steel flame arrestor for a dominator carb, and when I got it, it only flowed 830 CFM, after the mods it is good only to 1185 unrestricted cfm. BTW: it is 10" around and 3 1/2" tall, think about what you have.  TIMINATOR
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Offline David

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Re: Velocity Stack Vs. Scoop
« Reply #52 on: November 23, 2011, 07:36:55 AM »
Thanks for that explanation...
As I stated, I know nothing about this kind of stuff and just asking questions...
Please don't confuse my ownership of this forum with me thinking I know jack... I know computers and web stuff and enjoy learning from you guys to make my stuff better...
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Offline Kona Kandi

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Re: Velocity Stack Vs. Scoop
« Reply #53 on: November 23, 2011, 08:01:48 AM »

Please don't confuse my ownership of this forum with me thinking I know jack...


Hey, I know Jack... He's a great guy :biggrin:
It doesn't really  matter whether you win or lose...
as long as you look good doing it.

Offline David

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Re: Velocity Stack Vs. Scoop
« Reply #54 on: November 23, 2011, 08:21:15 AM »

Please don't confuse my ownership of this forum with me thinking I know jack...
Steve knows Jack too!!! He has the shirt to prove it!!!


Hey, I know Jack... He's a great guy :biggrin:
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Offline 78_Tahiti

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Re: Velocity Stack Vs. Scoop
« Reply #55 on: November 23, 2011, 06:39:45 PM »
Hey Tim! back to the cowl induction thing for a minute. I remember reading about testing the whole cowl induction theory, that was done quite a few years after GM introduced it in the 70's. What I got out of it was, GM prolly only gained 1 or 2 percent performance gain with the cowl induction, and most of that was due to the fact, there was a 2" spacer added between the carb and air cleaner, and it closed of most of the hot air under the hood going to the airbox. What type of scoop/filter setup do you see as most beneficial for a decent breathing, normally aspirated, lake Hot Rod.
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Offline TIMINATOR

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Re: Velocity Stack Vs. Scoop
« Reply #56 on: November 24, 2011, 04:49:06 PM »
GMs cowl hood got cool air to the carb, but the spacer above the carb hurt the cfm of the carb, or they would have gotten more hp. The main cowl hood thing was for NASCAR and roadrace cars, they had taller manifolds, so they didn't need the spacer. Carburators pull air from about 15-20 degrees BELOW the flat of the aircleaner mounting rim. With a choke horn the air still pulls from about 15-20 degrees below the choke horns edge. On anything smaller than an 800 there is no primary restriction, on an 850 it only amounts to about 7-9 cfm. Removing the choke horn, and removing the aircleaner ring lip and rolling the edge down is good for as much as 25 cfm depending on casting irregularities. The hp series carbs design leaves a bunch of airflow on the table, so to speak. a better design is to radius the air entry smoothly from the venturi vena contracta to the air cleaner flange, which would be removed, then align the scoop with 4 or more 1/8" roll pins, not that I have ever tried that........ Remember: I don't lose well either. Just for info, the 1050 on my 22 Daytona flows about 1300 cfm without modifing the venturi or booster. It will do more when finished. I have offered before for the locals to come by the shop (in Avondale,AZ.) with their flame arrestor/ scoop deals for a free airflow, NO ONE HAS EVER TAKEN ME UP ON THAT!!!! The offer still stands...  I have made the same distributor offer: I'll put it on the distributor machine for free to check it. I get about 2 a month. I have seen about 1 a year thats correct for the application. We charge $85.00 to correct the curve, mebbie a bit more if it needs a bunch of parts.  TIMINATOR
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Offline David

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Re: Velocity Stack Vs. Scoop
« Reply #57 on: November 24, 2011, 05:14:33 PM »
Hey Tim on the distributor can someone just send you theirs for you to fix it up?
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Offline 78_Tahiti

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Re: Velocity Stack Vs. Scoop
« Reply #58 on: November 24, 2011, 09:35:30 PM »
and I quote; "We charge $85.00 to correct the curve, mebbie a bit more if it needs a bunch of parts.  TIMINATOR"

I would say yes! David! Tim, what your addy in Avondale? I havent had access to a sun distributor machine for a long time. I have one I need to send you to recurve for my barge. Feel free to PM me if you wish. Steve Mac
If It Floats, F@cks, or Flies, Its Cheaper to RENT IT!

Offline TIMINATOR

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Re: Velocity Stack Vs. Scoop
« Reply #59 on: December 01, 2011, 06:56:12 AM »
Sorry, been busy out of town, picking up / delivering work in Havasu,and Laughlin. Address is: 3209 N.107th.Ave.  Avondale,AZ. 85392 623-877-8553  We are a COMPLETE engine building shop, and do mild to race pumps, glass work, setbacks, new and trade-in parts. Call. We send stuff anywhere, carbs distributors, pumps, etc.  THANKS!   TIMINATOR
MODESTY IS A CRUTCH FOR INCOMPETENCE!

 


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