BBC Manifold Runner Parameters

[SchmidtMotorWorks]

I am working on a CAD model for an intake manifold for BBC with conventional heads that I will make the patterns for this summer.
I have the concept worked-out but since I am a more of a manufacturing guy than a porting, flow-bench and racing guy I am making guesses about some of the parameters. I hope some of you could give me some advice on some of these parameters so that I can plug them into the CAD model and see how it looks with realistic numbers.

Here is what the model looks like now.



Any comments to improve on the concept are welcome.

The overall height is 9.0"

The current runner lengths (along the shortest side) are: the shortest is 5.8" on #3 and the longest is 7.2 on #7

The opening of the runners into the plenum is 3.0 x 2.0 with 0.5 radius corners.

The dimensions that I would like to tighten-up first are:

Are the runners too long, too short?
How thick should the divider between the runners be on adjacent runners?
Runner height and width at the head. (assuming 0.040" casting tolerance)
Bottom of intake port level from bottom of head.
Runner height and width (or area) at the manifold plenum.

I will post new images, with the new dimensions as it develops.

I don't really have a specific application in mind, just 4500 series carb and abilty to have a tall manifold.

[cboggs]

Wow,

This is quite a project, .. I'm wondering why you didn't hire someone
the engineer this for you? Is this a product that will be offered for sale like your
tunnel ram manifold?

There's several parameters you'll need to define to do a project like this.

First & foremost, what is the intended application? 540-596 big blocks, .. rpm range,
etc. Runner length and the size at the plenum, cross section in the port,
and exit cross section are defined by the application.

The divider should be as thick as you can make it, .. the thicker and bigger
the radius between the runners the better.

Curtis

[SchmidtMotorWorks]

This is quite a project, .. I'm wondering why you didn't hire someone
the engineer this for you? Is this a product that will be offered for sale like your
tunnel ram manifold?

I ask for advice here because I am very impressed with the quailty and thoughfullness of the answers given to other questions posted here. The only guy I know that really knows for sure the answers to this stuff reads and posts here anyhow.

I see that most questions get confirmation from others that share an opinion and when someone is off base there are usually second opinions.

Really, I don't know where I could get better advice.

When I read postings that review the design of cylinderheads, it becomes obvious that the people that finish and use these products know or care more about the details than the manufacturers.

Secondly, I haven't been that impressed by "Engineers" abilty to solve problems. I worked at Honda on the Indy engine program as a prototype machinist. I watched "Engineers" struggle to understand and solve problems that had been solved decades ago by illiterates working on drag racing engines. Given a choice between an Engineering based value and the rule of thumb advice from someone that has a stack of junk manifolds in the corner and has thoughtfully made a ton of chips with a die grinder, I'll take the die grinder guy everytime. If he confirms his results with some formulas, all the better.

[SchmidtMotorWorks]

First & foremost, what is the intended application? 540-596 big blocks, ..

Good question, I am thinking that the target displacement would be the 540, (4.5 x 4.25), 14:1, a 1050 cfm 4500, with a cam that has a HP peak about 7000 rpm.

I am thinking this design might fill the gap between single plane and tunnel ram for engines 750 HP and up to?.

[OldSStroker]

This is quite a project, .. I'm wondering why you didn't hire someone
the engineer this for you? Is this a product that will be offered for sale like your
tunnel ram manifold?

I ask for advice here because I am very impressed with the quailty and thoughfullness of the answers given to other questions posted here. The only guy I know that really knows for sure the answers to this stuff reads and posts here anyhow.

I see that most questions get confirmation from others that share an opinion and when someone is off base there are usually second opinions.

Really, I don't know where I could get better advice.

When I read postings that review the design of cylinderheads, it becomes obvious that the people that finish and use these products know or care more about the details than the manufacturers.

Secondly, I haven't been that impressed by "Engineers" abilty to solve problems. I worked at Honda on the Indy engine program as a prototype machinist. I watched "Engineers" struggle to understand and solve problems that had been solved decades ago by illiterates working on drag racing engines. Given a choice between an Engineering based value and the rule of thumb advice from someone that has a stack of junk manifolds in the corner and has thoughtfully made a ton of chips with a die grinder, I'll take the die grinder guy everytime. If he confirms his results with some formulas, all the better.

Hmmm... I don't agree with your conclusions...but that's another subject.

Honda seems to have gotten past most of those problems in their F1 and IRL engines. Wasn't one of Honda's goals to expose new, young engineers to the racing program to help them get their feet wet? These folks were not making the decisions, but they were there to learn in a stimulating environment. That works. I was exposed to a somewhat similar situation long time ago.

Perhaps you should get involved in engine design with one of the better engine simulation programs that uses intake manifold type and dimensions in it's calculations. As you become better at using it, you may be able to determine what a given engine likes as far as cross section, runner volume, taper and of course length. The manifold will probably be best on a limited range of displacement, rpm, etc. as cboggs said.

If your plan is to produce a manifold for sale, you need to do a bunch of on-engine development with it. My thought is that you may be trying to reinvent the wheel here. If I were attempting this project, I'd look closely at single-plane BBC manifolds modified by folks like Keith Wilson and Larry Meaux (maxracesoftware). Study what they have found to be successful, and maybe go from there.

As far as state-of-the art carbed manifolds for stuff like Pro Stock, you won't even be able to get a look at one!

This is certainly and ambitious project. I hope you have also considered the manufacturing costs involved, as well as the market.

Good luck.

[SchmidtMotorWorks]

Honda seems to have gotten past most of those problems in their F1 and IRL engines. Wasn't one of Honda's goals to expose new, young engineers to the racing program to help them get their feet wet?

The Engineers in this circumstance weren't young or inexperienced, they were new to V8s at the time.

This is certainly and ambitious project. I hope you have also considered the manufacturing costs involved, as well as the market.

I have already made a manifold, here is a slide show of the process.

http://www.schmidtmotorworks.com/manifo ... story.html

The work really isn't very difficult if you have the right equipment. The hardest part for me is all the sanding.

The one I made before is much more difficut than the one I am planning now. This manifold design will require fewer sand pieces to mold it.

The main idea I am wanting to test in this manifold is if there is an advantge to a runner opening that is more vertical than current designs.

Having worked in the mold business for a long time, I have learned that easy to manufacture shapes have a much larger role in product design than most people would guess. Profitabilty for me is a secondary issue, I mostly just want to make something original.

[shawn]

I've always wanted to do something like what you are going to tackle. The problem that i have always found with "production" manifolds is that they "fit" everything and apply to nothing. lol. Most are designed with compromise in mind. Shorter design for hood clearance and smaller cross sectional area for better response on smaller motors all go into design parameters for the "big" guys. The Dart and Brodix manifolds have got more towards a true race type manifold, but still leave a lot to be desired in a final product. If they were as good as they claimed people wouldn't be spending all the money to get them "right" after spending the chunck to buy them to begin with. As Curtis and the others have stated, finding a niche to build for would be the best thing to do and then build it without any "limitations".
Also if you need anyone to test a final product for you, let me know!
By the way, that tunnel ram of yours is a neat looking piece. Do you have any testing done with it?
shawn

[SchmidtMotorWorks]

Do you have any testing done with it?

Thanks, not yet, maybe soon, I just made some improvements to the patterns so that the flanges can be cut down to fit more heads than just the Profiler.

I've always wanted to do something like what you are going to tackle. The problem that i have always found with "production" manifolds is that they "fit" everything and apply to nothing. lol

If you are serious about making a manifold, let me know, I can get you started in the right direction and avoid a big learning curve.

About product design, I have the same thoughts, I think many things are made the way they are just because it is the cheapest way to make it profitably. I think manifolds have such undersize runners becuase of the poor control of the position of the ports in the casting. They just make them small enough so that they don't overhang the ports. If you hanen't ever been to a foundry, go, you will be amazed that anything of value comes out considering how rough and crude the proceseses are.

Some examples of compromise and "doing the way it was done before" are seen in crankshaft counterweights. The way 99% of counterweights are designed is the way that it is easy to forge and cheap to balance. The funny thing is that many billet crank manufacturers copied the shapes of the forgings because they didn't understand the theory of couterweighting. Old Moldex cranks come to mind.

When I look at single plane manifolds and how similar they are to the early designs and then I when I go to the foundry see how the patterns are made to produce them it is easy to see why there would be so little change. This is further solidified by the foundry telling me that they strongly prefer the patterns be like the existing ones.
It is really easy to make a pattern for a single plane manifold with a band saw and a table saw. The manifold I am planning to make next requires CNC milling to do it in reasonable time, that type of work ie easy for me as I don't have good coordination for hand work like proting. Most pattern shops prefer to work from drawings rather than CAD so some shapes are difficult for them to make.

[SuprStk400]

Very impressive manifold! If you keep at it they will come! I agree, Most production manifolds are a compromise to fit anything.

If you get one done I would be interested in a raw casting and I will machine it to fit and test it on a 509 that currently makes 840 hp with small high velocity oval ports that i ported.

Call me 570-916-4620, Drew

Daylight eastern time

[RGL]

I have already made a manifold, here is a slide show of the process.

http://www.schmidtmotorworks.com/manifo ... story.html

Thats a sweet looking piece , I kinda had you figured to be a little older than you looked in that opening picture , I guess you never know where you will find the next child prodigy. LOL

I did some flowing one time on a 351C tunnel ram against a Windsor style port ( port opening filled in to match head) , and the results werent all that impressive , it was about 10% down from the single plane cast piece I was comparing too. The manifold comes out , and then rises up kinda sharply to the plenum , I figured it didnt like that angle as the reason( comes out pretty vertical ) , is this what your trying to achieve ? Sorry , wish i had some real useful info for you, but I am mostly an observer here.

By the way , would you be interested in making another manifold for a diffrent application ?

[SchmidtMotorWorks]

The manifold comes out , and then rises up kinda sharply to the plenum , I figured it didnt like that angle as the reason( comes out pretty vertical ) , is this what your trying to achieve ?

The reason I think there might be some advantage to the runner openings looking up is that the air fuel mixture doesn't have to turn as much to get into the runner. Maybe there would be less fuel seperation, maybe it wouldn't matter. The way I modeled it uses a curve method called "least tension" this makes the largest radii of curvature possible for a given start and end.

I have collected some of the numbers I need to finish the model as soon as I plug them in I'll post an image of the complete piece.

By the way , would you be interested in making another manifold for a diffrent application ?

Maybe, what do you have in mind? If you have some wood working abilty, I can guide you through doing it yourself. If you know CAD CAM, even easier.

I'm not sure yet when I can start another project. This month I am deciding whether to rent a new shop here in Southern California or move to Ohio where I can buy a small shop. The cost of rent is here is high for my hobby but I haven't lived where it snows for 20 years. Does anyone here live near the Xenia track in Ohio? I'm considering Waynesville (my real job employer has an office in Milford). It reminds me of how Norwalk was in the 70's (some great old times for me) maybe (absolutly, for sure) Jr dragster for the kid.
[/quote]

[cboggs]

Jon,

Wondering, .. what's your "real job" ?

Ohio isn't bad, .. in fact it's nice, .. I run my Formula ford at Mid-Ohio
sports car course, .. and spend two weeks a year there for the SCCA
run offs, ..

I'd be very, very interested in learning more about the process, ..
the "ins & outs" etc, ..

What CAD do you use, .. I'm trying to teach myself Surfcam and Mastercam for my CnC work.

Curtis

[SchmidtMotorWorks]

Wondering, .. what's your "real job" ?

I work at UGS as a software application engineer for the CAD software called "NX". I write project plans and do testing mostly.

[70MC]

Does anyone here live near the Xenia track in Ohio?

I live in Youngstown(Austintown is a suburb of Youngstown), about 2 hours from Norwalk and about 4-5 hours from Xenia. I have relatives in Xenia, and have been by the track there, it is called something like Kilcar. Can't remember if it was this site or another one, but there was someone from Dayton that posted, which is right by Xenia.

Land and buildings can be had for cheap in my area, as the Youngstown area was known for their steel mills, and they are gone, so the area is somewhat depressed.

I work at a CNC machine shop (i have no CNC skills, i run parts) in an industrial park in Ytown. Rumer around the shop says the owner got the land free, to build on, to help bring in work to the area. Although he has said to me, he was thinking of moving the shop out of the city to save on city taxes.

[Rick360]

In a conventional 1x4 manifold there is a lot of the flow for one runner provided by the other runners. They all flow back and forth sharing mixture as well as drawing from the carb. A reverse pulse from one runner can flow across the plenum to help feed another runner.

With the manifold in your drawing, the reverse pulses would cause a lot of turbulence in the plenum, being directed back up at the carb. It would also be difficult to share mixture between runners having to turn 180*.

Just a couple of my thoughts.

Rick