A lot of work there. Nice that you put time, effort, and monies into it.

Interesting, do you know the free length and/or spring rate? Which end would you remove a coil from?

I've definitely thought of the option to use something existing. Part of me likes that route, part of me says this project is for learning and advancing my skills.
Thanks for the images and ideas.

Some progress with a few more steps complete. Welded the back plate to the trumpets and faired the inner surfaces.
Moving on to the plenum. Need to decide on what material to build it from. Aluminum tubing and sheet metal or carbon fiber?

Works well. No oily vapor mess in the engine compartment and I don't see much oil in the intake run off the compressor.

Doing some start-up and idle tuning yesterday, and observed the oil pressure when warmed up. Right around 2 bar when at idle. I recall something like 4 bar when cold with some light engine load.

Thanks Pascal,
It is progressing nicely. Nice to not be in a hurry. Systematically tooling and building one step at a time. Practice and dry runs to help feed the end product.
Will start designing and working the manufacturing process for the plenum. Might try some novel build techniques?

Practice to dial in the speed of the positioner, rest position bars, amps, and radiate heat.
Makes a big difference with the speed. Too fast and not enough penetration and the filler rod does not take. As seen by the first picture. The part was rotating counter clockwise.

Money shot.

Runners are tacked and it is now freestanding. Now to figure out the welding sequence and any preheat.

Rolling out some dimes.

Doing some positioner (rotory table) prep, coupons, practice and dialing in. Set the height of the machine and hand rest location. Made a centering fixture to index the trumpet and mini hold down clamps. This will allow not only pushing filler rod keeping the part in place, but a horizontal position...

Glad to see the site backup. More fitment work to get the tubes in their happy spot. Index pins so I can remove and replace the plate back to it's original location. Mandrel tool and dead blow to true up the shape and inner dimensions to match the intake flange runners. Introduced the mock-up plenum...

The plenum back plate is now fixtured to the head. Need to add some indexing pins, but the squares and majority of the clamps are gone.
Trumpets and runners are on deck.

Got the squares from Fireball Tools. They were a Diy precut weld up kit. His cast aluminum and iron ones are really nice.