Custom Intake progress. (pics)

[2802NR]

Got started on my intake manifold friday and I thought I'd post some pics. I still have to mill 4 of them for clearance between #1, #2 and #5, #6 but here are the runners:

 

 

 

and some machining pics:

 

 

 

The runners are just over 7 inches and are tuned in length using the grape ape racing formula for a helmholtz resonater effect. They have a 1.7 degree tapered bore which matches my mildly ported N42. Ill try to continue posting pics as I fabricate the flanges and plenum.

[BRAAP]

Very very cool.

Nice to see soemone adding the taper as well.

Are you startgin your taper from behind the valve seat or the port entrance from the manifold?

[2802NR]

Unfortunetly the port entrance-to-valve isnt a very accurate taper. I had a local machinist work it and he did a good job on the short-side radius but they ended up at about 1.42 in. entrance I.D. wich isnt very close to the 1.73 in.(is that right? I cant remember off my the top of my head) L28 Intake valve O.D. Anyways, I'm hoping this will increase my power band so I can get the most out of my cam. Right now it prety much falls on its face around 5200 r's. Ill be installing MS2 at the same time so that will help as well.

[thehelix112]

Looking good!. This is for a forced induction application I presume?

 

Will be very interested to see your plenum design.

 

Dave

[1 fast z]

What harmonic are they designed for? I would guess either 4th or 5th. 7", well depends on the CFM flow of each port, etc, but that would be like a 4th at 8000 RPM, or somewhere around there? What is the minor or major diameter of the runners? (I could figure each out, as long as you give me one of the diameters.)

[240Z Turbo]

The runners are just over 7 inches and are tuned in length using the grape ape racing formula for a helmholtz resonater effect.

 

Very nice and glad to see someone taking the extra step to cnc those runners. Staying true to a helmholtz resonator, I do believe you should not have the plenum connect more than 4-5 cylinders, otherwise those principles do not hold.

 

I don't think you will have any trouble with your design and you should see some nice gains. BTW, make sure to use 1/8" and not 0.090" for the plenum if it is to be boxed.

[2802NR]

helix, This wil be used on a 10.4-1 NA motor with a .460 270/280 cam.

 

1 fast z, The min. I.D. is matched to the head port dia at 1.420 in. and the entrance R is .25 so that ends up at 1.8388 runner entrance I.D. Now I had to use a harmonic pressure wave set of 4 due to limited space in the engine bay. 1.7 degrees may be an extreme amount of taper but it shouldnt inhibit airflow, it may however exceed the limit of what a taper can do to help airflow.

 

Here is the formula I used Wich was the Grape Ape Racing formula taken directly from the intake manifolds chapter of "How to tune & modify engine management systems" by Jeff Hartman:

 

[(ECD * .25 * V * 20)/(RPM * RV)] - (D/2) = L

 

ECD= Effective cam Duration

V = Pressure wave speed (speed of sound)

RV = Reflective value (the utalized pressure wave set)

D = Runner diameter (I wasnt sure on this because of the taper so I used the averege diameter over the given length)

L = Runner length

 

[(420 * .25 * 1300 * 2)/(6000 * 4)]-(1.64/2) = L

 

273,000/24,000 = 11.375 - .82 = 10.555

 

valve seat to mating surface = 3.511 (the book didnt specify on this so I used the short side radius)

 

10.555 - 3.511 = 7.044 runner length

 

Now as I said earlier, There were a few variables which the book wasnt too specific on so I used some guess work but it will be interesting to see how it works out bieng my first shot at it.

[2802NR]

240turbo, It will be a split plenum design. My computer didnt save my latest cad re-vision but here is an older one I still have:

 

 

I had to re-draw the head flange for header clearance and I made the plenum volume alot smaller than this version. The plenum also extends 1in. past #1 & #6 for better air supply in the newest version wich I'll have to re-draw again.

 

Thanks for all the input guys!

[The Revelation]

sorry this is a little off subject but im really glad to see a cad design it helps put things into perspective, thanks!

[240Z Turbo]

240turbo, It will be a split plenum design. My computer didnt save my latest cad re-vision but here is an older one I still have:

That looks very nice. Just out of curiosity how will the TB's we situated?

[2802NR]

I'm going to use a dual 48mm TB off of a '88 TPI corvette. That way both plenums will be 100% independant of each other. Ill try to get the final cad drawing up once I re-draw it.

[jeffp]

I just went through a cylinder head setup myself. You may want to consider opening up the runner at the head to 1.5" that way when/if you do the porting on the head the intake will fit the head well. The diameter of the gasket should do nicely. Just a suggestion, and you can still machine the runner to size.

[BRAAP]

If you take Jeff Hartmans advice about taper, (which is what 2802NR is following), from the valve seat using the L-28 valve and seat, the opening of the port where the manifold meets the head ends up being around 1.7”, quit a bit more than 1.5”

We are also in the process of building a 4 cylinder intake for an L-20-B using Hartmans book. We plan to use the 1.5 degree taper from the valve seat out, or at least the best we can.

[olie05]

why not use two seperate throttle bodies?

I think two throttle bodies would look cool, but i guess getting a proper linkage for them would be alot harder than the TB you are going to use.

 

Have you measured clearance against the fender with that setup and added the length of the vette throttle body?

-Oliver

[2802NR]

Once everything is finished and on the car I'll have a little under 3 in. between the TB and the drivers side strut tower, but it is mostly behind the tower due to engine placement so I will probly rout it backwards and end up with a filter near the master cyl. which isn't very ideal but my header is ceramic coated so engine bay temps are reasonable. I thought about modifying a Z31T hood scoop if I end up with my filter in this location.

[JustinOlson]

Any update on this thread? Would you be willing to machine a set of runner/velocity stacks for my L28? Those look really nice.

 

Regards,

Justin

[2802NR]

Just waiting for some free time on the mill. This is a very busy time of year at my work. I never intendid to sell one, or parts to one. It would be more cost effective to buy a manifold from Lonewolf performance since I would have to charge a shitload to break even. But if you are just interested in a set of runners we could probly work something out.

[JustinOlson]

I'm really just interested in a set of tappered runners. No big rush for me. I'm busy with other projects at this point.

 

I'm going to be doing a CNC'd head flange for my l28. Heres one I just did for my audi project:

 

[2802NR]

That looks great! where are you getting the material for the fuel rail?? Whats it called? I am having trouble finding somthing that will work for mine.

[spotfitz]

That looks great! where are you getting the material for the fuel rail?? Whats it called? I am having trouble finding somthing that will work for mine.

 

http://rossmachineracing.com/