Sheet metal intake building

[sanger351]

Anyone have some good references for a how to build your own intake manifold?  I have been doing some searches but I have not really found anything useful.  Links, formulas, books I am open to anything.  Thanks

[maguromic]

Without knowing your application it’s hard to tell what will work and what wont work.  I can say there are lots of variables and physics that need to be considered to get the optimal design.

Getting the correct harmonic resonance is very crucial.  The second harmonic designs generally return the best performance followed by the 3rd.  After the third its very minimal the gains you will get.  Also there has been a shift towards more plenum volume lately, and I don’t think you can go wrong with more plenum volume, but you certainly can go wrong with less.

Some things to consider along with your engine parameters:

Type: What is the manifold configuration (EFI, Carburetors or)?

Flow with Runner%: The percent that the cylinder head flow increases or decreases when flowed with the manifold attached.

Runner Turn: The amount that the runner (excluding the turn in the valve area) turns in degrees.

Fuel Dist Rating: The quality of the fuel distribution, For example an EFI is a 10 and a typical cross ram would be a 0
.
Manifold Air Temp: The manifold Air Temperature. This value is used to calculate the optimum length of the runner.

Total Throttle CFM The actual throttle CFM at 1.5 hg.

Taper Included: The runner taper from the valve seat or choke area (if it has one) to the runner opening.:

When I was running the numbers for my XO motor manifold, I found that I needed different length runners for different conditions.  So I decided to make a variable runner intake where I would use spacers to increase runner length depending on the conditions.  My IRL Chevy engine uses the same  concept to adjust the runner length (see picture).

If you want PM and I can give you hand.

[sanger351]

I am a high school auto teacher so any books and info I can get my hands on that is over my head is great.  What resourses are out there to learn this?  Last year I took a trip to Italy and went to the Ferrari museum in Modena.  They had past F1 engines out on the floor with variable length carbon fiber velocity stacks and centered injectors.  As you opened the throttle on the engine a bell crank system changed the length of each runner.  I could have spent days there, but some people that I was with wanted to look at more old rocks. 
I am obviously not looking to build F1 quality stuff out of the chute,  I am just looking for the basic info to start this learning process. 
I'll PM you with some info and would appreciate any help getting pointed in the right direction. 
Thank You
Sean

[Jonny Hotnuts]

Aftermarket manifolds have a ton of HP research, are dyno tested, readily available and for the most part relatively inexpensive. I have seen a motor that had a custom sheet manifold (very expensive) that would of worked great on a motor in the 7-10+K range. This motor however would never see anything over 6K and imo the reason the motor did not make the power of years before (or speed).

If you are building a rare motor without aftermarkets available making one should not be all that difficult if you have some skills and tools. If it is the case that an aftermarket is not around I would find a performance motor that is close to the bore X stroke and RPM range that you are looking for and use its manifold as a rudimentary guide to making one regarding length and size of the runners.

Maguromic is correct about the resonate tuning, but this is a black art altogether. It would be nearly impossible for someone without the million dollar engine design software to correctly ascertain the correct volume of the airbox and plenum to take advantage of 1st, 2nd or 3rd order harmonics. I build a larger airbox for my busa motor because I knew even a stock 1300cc motor can gain HP from a larger box so I increased volume 15% over stock and then increased for the % volume of the larger stroker motor (1507cc). But this is only a guess. If Maguromic has a formula for being able to correctly tune for resonate Hz I would love to know it. I have even spoke with Dr Mayfield regarding this and still don’t have any solid answers.

It again is my recommendations that you go with a good quality aftermarket as apposed to the potential gain-loss that can be made from a homemade intake.


-JH

[sanger351]

The class we want to run in does not allow engine swaps.  All of the good aftermarket manifolds used for our engine were designed on a later head style that has a different intake bolt pattern and runner design.  If we can run the later head and not be disqualified we would do that.  I would be very disappointed if we were lucky enough to set a record some day only to have it protested because the intake bolt pattern is different.  Valve angles, head bolts, exhaust ports/bolt pattern are all the same just not the intake.

[maguromic]

JH, I use Lotus engineering software http://www.lesoft.co.uk  that one my Indy car buddies have.  The algorithms they are using are derived form all the years of F1 experience.  I don’t think its that much of a black art if you have the right data to work with.  This software package takes into account even the valve stem diameter.  When Darrin Morgan was with Reher Morrison I ran some of my numbers by him and he said that they were within 2% of his dyno numbers. That’s close enough for me.

Sanger 351, The placemat of your nozzles will depend on what you are running, fuel or gas.  I run gas and I have my nozzles very similar to the Ferrari engine you saw. Its all about trying to atomize the gas a little better.  Since you are a teacher they have a free academic version.  It might be  worth a try to contact them.  Or get one your college professor buddies to get it for you.

[John Romero]

The class we want to run in does not allow engine swaps.  All of the good aftermarket manifolds used for our engine were designed on a later head style that has a different intake bolt pattern and runner design.  If we can run the later head and not be disqualified we would do that.  I would be very disappointed if we were lucky enough to set a record some day only to have it protested because the intake bolt pattern is different.  Valve angles, head bolts, exhaust ports/bolt pattern are all the same just not the intake.

The different intake bolt pattern is all it takes. Thats considered a motor swap

[willieworld]

IF everything is the same except the bolt pattern how about running the manifold that you want and changing the bolt pattern to match your heads   willie buchta

[sanger351]

Yeah thats what I thought.  The rules do say "may determine" and I have read that people look past the chevy vortec heads, and even the small block ford heads when the number of intake bolts changed.  However if push came to shove I would think that the protest would win.

[sanger351]

I am sure I could make adapters but the port angles did change slightly.  I am looking at all options.  Besides as my students tell me "If it is not custom, I don't want it."

[Stainless1]

351, send a question to the scta tech guy, tell him what you were thinking, see what he says, the worst that can happen is you find out you have to build your own manifold    Use the system to help you, you may figure out which side of the protest you are really on. 

[dwarner]

rulebookinfo@scta-bni.org

DW

[Milwaukee Midget]

Sure would help if you'd spill the beans on what you're building, but we understand, secrets can be fun. Keeps us guessing, anyway!

I am sure I could make adapters but the port angles did change slightly.  I am looking at all options.  Besides as my students tell me "If it is not custom, I don't want it."

Whipping up a manifold from scratch that flows and compliments your heads could leave you with hours of flow bench time trying to get it right.  My argument for adapting an aftermarket manifold is that despite what you're trying to make it do, you're starting with a known quantity, and therefore you have fewer variables - by starting from scratch, you have almost nothing but variables.

But if you LIKE variables, here's something else to consider - If you made an adapter, would the port angle differences give you an opportunity to port-match to the heads in a way that might be to your advantage?
 

[Y.B.]

     Sanger 351,

                I read your post with interest. I saw a magazine only last weekend,that goes into a lot of detail about fabricating custom inlet manifolds, but there is only one hitch, the newsagent is located about 13,500 miles from where you live!
                                                       I live in Australia, but i'd be more than happy to buy a copy and send it to you.
                    I am a member of the D.L.R.A., and i'm in the process of building a car to run in Gas Altered.The car is a Holden Torana [G.M.] coupe, very similair in size and shape to a Chevrolet Vega, and I am using a Nissan six cyl. in-line engine. This is an E.F.I. engine, and I modified a standard inlet manifold,by sectioning the plenum,machined a new flange which was then welded to the plenum, to which mounts another machined flange, which carries 3 standard throttle bodies.
                                                                                                     If you care to send me your details, I will get the mag. away to you a.s.a.p. My E-Mail address is with my sign on name,Y.B., on the members register of Landracing.

                                            Regards,  Garry Brennan


                                           " Life's just fine, in a straight line!"
                                                       

[wolcottjl]

You can read through a website that is frequented by people that do builld sheet metal intakes as well has most everything else associated with cylinder heads.  www.speedtalk.com - A lot of top line head porters post on the site.  The search engine is not that great but there is a lot of information buried in their forums if you search enough.