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Technical Home Made Intake Tech Wanted

Discussion in 'The Hokey Ass Message Board' started by Robert J. Palmer, Dec 15, 2019.

  1. I want real life experience from people who have built/raced built intakes.

    Here is what I am doing-
    Vintage oval track car.
    Must run single carburetor, leaning toward 500 C.F.M. Rochester 2 BBL common oval track carburetor
    261 Chevrolet 6 bored .040 over
    848 head ported surfaced .052 75cc chambers

    Looking for advice on plenum size/shape
    Intake runner length/shape

    Robert J. Palmer
    loudbang likes this.
  2. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    No experience with that. I think I would build a sort of tunnel ram to try to get fuel evenly distributed. Top plate removable so you could play with vanes and plenum size after looking at pluges.
    tractorguy likes this.
  3. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,737

    jimmy six

    I will send you a photo of one when I’m well enough. It was used on a GMC but very similar. Was also made for a 2 barrel.
    I know may sound dumb but make sure you know the tracks rules on the directions of the carb and it’s height. I’m not talking the allowable spacer; since it can be homemade, there is no height limit, you add the allowable spacer, and then you win.....Kaytee bar the door. Your cheating.....
    loudbang likes this.
  4. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,051

    from Brooks Ky

    I would think on an inline 6 that getting equal fuel distribution to the end cylinders would be the most important issue.
    Even V8s have been found to have a problem with getting equal fuel to front/rear cylinders. Thats why OEM manufacturers went to putting an injector at each cylinder rather than the central throttle body mounted like a carburetor on a manifold. Getting creative (think Smokey Yunick) with the carb and intake should help. It doesn't do any good to flow more air if you can't get equal fuel to all cylinders.
    tractorguy and loudbang like this.

  5. I will shortly be building a 6x2 intake using a fuel injection manifold (ot intake on a 1962 engine) with .250 aluminum plate for the plenum and carb mounts. I have all the pieces, just have to just have to cut and paste......
  6. I already have the series rules, rule simply says "Single carburetor only, can not be mounted side ways" , I was thinking of using a 2x1 and building an adaptor to a single carburetor.
    Like an upside down Edelbrock slingshot.

    That's my concern, I don't want to step on the throttle and have the engine bog.

    Attached Files:

    ironrodder likes this.

  7. The first rule in the book this class
    -Showcase and preserve the history of our sport through the competitive racing of original reproduction and replicas of the racecars of yesterday.
    If it is your intent to invest in the latest and greatest parts and technology to be the big fish in a small pound, this is not the class/series for you. If it is your goal to dominate the field every time you pull onto the track and win by a lap, this is not the place for you. There are plenty of tracks that will always welcome new 602 sportsman and modified drivers with open arms.
  8. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    If the rules allow it, my thought was sort of like an exhaust collector. Three tubes pointing up in a tight circle to a plenum.. This is to encorage all ports getting equal fuel. Yes it is difficult to get fuel to #1 and#6with a central source in the middle on a flat plane
  9. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,737

    jimmy six

    I read this as the competitor I always am. I was assuming you were constructing one from tubing and they would feed to a centrally located “box” with a Holley style top for a flange. A Chev/GMC stock will always have 2 rich cylinders, 2 lean cylinders, and 2 correct cylinders... it’s the nature of the beast. If you could raise the box high enough you could bring the center tube to outside to help with equal length a bit and that’s a good thing. If you could convince the officials that turning a carb was not a competition advantage you would be way ahead. It supposed to be fun and you are only running against other vintage 6’s and flathead V-8’s hopefully.

    Anyway here are 2 photos of my tubing manifold. Like I said it’s for a GMC and with a Brazwell modified 500 Holley that flowed over 700 cam it was a real winner. If doing again I would have split the tubes entering the box to add more venturi effect as it enters the port at the head.....That’s how you work with any stumble on quick acceleration. 207279BF-F00B-437E-9FE9-909386924A28.jpeg 6795489B-6382-47D2-8515-8923ABAB08CF.jpeg
    saltflats and Robert J. Palmer like this.
  10. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,051

    from Brooks Ky

    Do the rules say you can only run a two barrel carburetor or that you can/can't modify the carburetor in some manner? I would think that a four barrel with small venturis would do a better job of atomizing fuel into the air so that the finer droplets could find their way to the end cylinders. Is any kind of injection allowable ?
  11. I am looking for ideas, what work what doesn't. I want to be true vintage style. Your intake looks good. Was it for an oval track car?
    I am the only person running the early Chevy 6. Everyone else is running a 250/292 Chevy 6 or a SBC.
    However they are in heavier cars and everyone must run a stock frame and leaf springs in the back.
    The winningest car in 2019 was a 39 Chevy coupe on a 55 Chevy frame with a 250 Chevy 6. The only time I saw it beaten this year was by less then a car length by a 350 in a 48 Chevy Coupe on a Stock Frame (Early Ford Front axle)

    No, Carburetor only.

    The Carburetor can not be turned sideways this is a new rule for this year I don't know why.
    Last edited: Dec 15, 2019
  12. Any two or four BBL carburetor.
    Rochester 2 BBLs modified to 500 CFM are common on street stocks and fairly cheep and pretty easy to work with.
    I like Holley 4BBL and the 4412 however they are very tricked up and expensive.

    I want a car other than safety looks like it was built in the early 60's
    Last edited: Dec 15, 2019
  13. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,737

    jimmy six

    The Carburetor can not be turned sideways this is a new rule for this year I don't know why.[/QUOTE]

    I’ll bet the carb on the 39 coupe on a 55 chassis was sideways because it wasn’t illegal and the V-8 don’t like loosing to six’s.

    Also from what I’m reading these guys are serious. We ran a 62 Chevyll on a 57 chassis, ever think we had a setback advantage back in the early 70’s....well..dah. Gonna be a tough one here.. good luck.
  14. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,414


    Ran an 1850 Holley on dirt tracks for years and mounted it backwards . Keeps the bowls full.
    The rules said a stock 1850 with the choke blade removed. No where did it say anything about being mounted forward.
    What about offsetting the inline 6 to the driver side? In the end it is up to the tech guy what he likes or not. Are you married to the Chevy? I would be running a 300 Ford 6 in a 57 Ford chassis .
    A guy used to run our Hobby stock class with a Granada body on a Crown Vic chassis with a 300 six. He was a top 5 car. Not a winner, when the track got slick he could run up front when the higher powered V-8' s couldn't get the power down.
  15. Mike VV
    Joined: Sep 28, 2010
    Posts: 2,411

    Mike VV
    from SoCal

    Hints -

    1. Think OUTSIDE of...just a simple square box..!

    2. Don't just build a square box for a plenum. Build it so that it helps direct the fuel toward the port runners. That means...NOT just a square box.

    3. Don't do it the simple way, just plug in a tube/runner to a square box..! Place it with purpose. Also, important, flare the tubes where they enter the plenum. NO...hard corners at the runner entrance.

    4. The plenum should be the same as, to slightly smaller in cc's than the cubic inches of the engine.

    5. Short runners help with high rpm power, longer runners help with mid-range power.

    6. The runners should be as close to the same length as possible (see the photo above and reject that design). Again, you may need to think outside of the proverbial box, especially for the center most runner(s).

    7. Don't make the runners out of tubes with hard square corners. Round is fine then shape to fit the cylinder head ports.

    Hope this provides you with some meaningful hints.

    tractorguy and The Shift Wizard like this.
  16. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,051

    from Brooks Ky

    If you are going to try to build a car that can win its share of races, you need to "look" at what others are doing successfully............and then try to see how you can improve rather than just copy what they do. One thing obviously is getting the fuel equally distributed. Another thing is a hotter spark to ignite it completely. A flat intake tends provide less fuel in the end cylinders on an inline six. I'm thinking that a plenum sitting higher than normal so the air/fuel flows somewhat downhill and with some plenum dividers installed under an optimized 4 barrel........might divide the fuel more equally. People in the sixties experimented with lots of things. As long as its a home made intake it should "look" acceptable. You can bet the guys up front regularly have a few tricks up their sleeves....

    Might install some bungs in the exhaust header so you can put a wideband O2 sensor in place "during testing" and read how well the mixture is burning in each cylinder. Just remove and plug the holes when going racing. Some people use different heat range sparkplugs in different cylinders to deal with variation of mixture between cylinders.
  17. I just reread the rules our class can run the carb. sideways It is the tube chassis cars V8 class that can't.

    The intake and fuel delivery are what I am thinking about I don't want build a intake that bogs the engine

    I have already found some things that will work to my favor in the rulebook

    These guys are friendly. Its a club free to join free to race.

    I have a long family history of oval track racing

    My Great Uncle Don Wyel (In Car) crewed for Sam Car on this A.A.A. Big Car (Indy Car) pre 1938

    Dad building his first car


    Dad preparing band new frame rails, for the cage of his second car

    The chassis for the second car. He got it to a roller and sold it. Just before he and my mom got married. Then started a third car. Note 180 headers

    Dad built this chassis with a Nova Sub-Frame fabbed S.C.R. crossmember to use Ford lower A-Frames 2"x3" tube. By the time Dad got it finished he and Mom were married a few years and found out they had a baby on the way (me). He sold the car before he ever drove it.
    tractorguy likes this.
  18. 402BOSSMAN
    Joined: Jul 26, 2015
    Posts: 343


    I have lots of experience in this arena. The problem I see is what is technically deemed era correct for the class? Is it subjective to what one guy thinks? Is there a year date cutoff for the parts to be used? Do they share visual examples?
    This Clifford Manifold looks like a well designed piece.

    I usually calculate what is needed for runner length, cross sectional area, airflow requirements, etc. If you are trying to be competitive sometimes its easier to work on the things they can't see if rules are strict on outward appearance.

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