I am going to build a new upper plenum to attach to the lower intake on my turbo v6 Mustang project, had planned on using 6 - 1.75" ID 3 " long runners to mate the plenum to the base that will bolt to the lower. I have been advised against using round tubing, was told it would stall the air, planning on running a machined bellmouth into the ports in the plenum. Should I modify the design to use oval tubing or will I be ok with such a short run?

 

The gt 40 intake uses a tubular design. Now you see a lot of rectangular runners though.

 

Provided that you've got a transition into the base where it's not going to have an overhang into the runner it should be okay. Reversion is a big killer of flow, and having "lips" is the biggest issue. As an example a 2X2 square intake port on a head having a 2" diameter round runner going into it would be fine, but the reverse would not be true due to the overhanging material. With it being boosted anything short of extreme circumstances shouldn't bother the system too much provided the RPM's where you want it to be. I'd guess your'e ditching a stock upper in order to get some RPM out of the engine?

 

The stocker upper has a long curved back wall and the back two cylinders see atleast 10 times the airflow amount as the front two when the system is under pressure, just burned a piston and want to make sure that doesn't happen again.

 

Ouch! Hurt it going for tens?
That sucks John.

 

You have a pic of the intake John, I haven't seen the V6 intake. You can buy runners but there pricy. Im in the process of making dies to make runners in a 12 ton shop press but they will be 2 piece and tiged together down the sides to make a runner. MMR is selling billet runners now but there again pricy. Im just going to use 12ga for the 2 halfs and then weld them together. The runners should have a taper to them for velocity.

#ad

 

Had just gotten rid of the crappy 2.73's and added some gear to arrest the launch bog, meth pump locked up, must have happened right after the dyno, made one pass @ 89 in the 1/8 and the rest were 85 mph scratched my head and ran it anyway, not so good, now I got this. Hard part is keeping all the LSX gurus around the joint from sticking one in the poor stang.

Charles, I have seen em hand formed before, two U channels. I am waiting to see what my water jet buddy comes up with, he is very creative sometimes, was just going to make an upper but that all might have changed.

#ad


#ad

 

Stock upper

#ad

 

Ford and their plastic intakes, but they do reduce the heat compared to metal.

 

Crazy they stick with that type of design kind of like a 5.0

 

Plastic intakes are great, when they're made by GM. That intake just makes no sense, being that it's a V6 and not an inline. Wonder why they didn't just do a 6cyl version of the 5.0 intake?

 

What you don't see in the picture is an inch in the port becomes a 1.75" square and they are all in line. My thought was to make a balanced upper and use a round port to feed each of these runners, I keep getting warned of the oddball sized inlet acting as a turbulent shelf so know I am think about making a flat plate that attaches to both heads and using oval runners to reach up into a plenum, where it will look something like my revision 2 drawing.

#ad


#ad

 

John the intake ports on those heads are the same as a C head or Navi head , take an old C head intake and cut a runner off each bank and build off of that, that will give you the head mounting flange then make some runners .

 

Looking forward to see what you come up with.

 

My machinist is building a mounting plate that will act like a base for the intake. Once I have that and the original intakes side by side I can start laying out my plan, looks like I have 5 - 6 weeks til I have pistons and rods here so I got's me plenty of time . Experimented with pressing round tubing into rectangular rounded corner tubing and that worked well, so that could work.

 

You could always make a transition in Solid Works. It would take some effort to do, and your machinist would have to be pretty darn good to make it happen but I would probably just hog it out initially and then go in with the die grinder and clean it up. Ahh the joys of a bridgeport

 

Working on a different project, I was faced with a similar challenge -- oval runners in the cylinder head, but building an intake with tubing for runners. I made a Solidsworks model and got some quotes from machine shops. Not surprisingly, quotes for a one-off set was not very economical. the approach I took could be a good option for you:

Raw material:

#ad


Cut three pieces that closely matched my desired dimensions:

#ad


Weld them together and smooth:

#ad


#ad


Shape of each end vs desired shape:

Runner in cylinder head:

#ad


Tubing:

#ad


Start with material and use wood (as a hammer) to start curvature:

#ad


Form the aluminum around the hammer form:

#ad


Cut to length (not a straight line because of the transition to oval) and finish forming aluminum into oval:

#ad


#ad


A little work with a die grinder blends everything nice and smooth!

#ad


A person could probably look at the four I did and tell me which was done first and last. They got easier and fit/looked better .

Have a good day!
Michael