No, I must let it go. I have to stop spending money. If you hear anything pls let me know.

Finally, it's starting to look like an engine again, lol


I had some custom spacers waterjetted to raise the carbs another 1/2". They give me more clearance between the carbs and fan shroud and should improve intake harmonics


At this point, I may or may not have her going in time for the VW Classic, and I almost don't care, I just want to be able to daily drive her again, that's the real enjoyment for me.

Looks Good!

Get her ready by September

Looking good!

What constitutes the optimal intake manifold length?

It's very engine dependent. As a general rule of thumb, the higher the RPM of the motor, the shorter the intake lingth. It has to do with wave reflections in the intake system. Basically you have pressure waves that "bounce" back and forth between the back of the intake valve and the entrance to the air horn. If you set the length up correctly, the pressure wave created by the intake valve closing travels from the intake valve to the air horn and then back to the valve in time for the valve to open again (in a certain RPM window), thus creating a "supercharging" effect where the VE can actually exceede 100%. That first wave reflection is called the 1st harmonic and the necessary length of the intake to take advantage of it can be quite short, so usually you aim for higher order harmonics, like the 2nd, 3rd etc. With each higher order harmonic the strength of the signal decreases, so you want to use as low of a harmonic as possible at what ever RPM you want to make max power. I have my 2nd harmonic set at about 7500 RPM, which is where I hope to make peak power. My 3rd harmonic is around 6000 RPM, and my 4th is around 4700 RPM.
It's part of the whole engine combination: the heads, cam, carbs, and exhaust must all be matched to work together, and that combination will have an inherent RPM range. Harmonic tuning to that RPM range further optimizes the combo.

so how do you get that perfect? Meaning, how do you know that you need another inch? Flow bench with the manifold and head bolted up?

How do you know the RPMs before engine has been dyno or installed in the car? Is there a formula for knowing what size?

No, this is unrelated to the flow bench, which gives static flow numbers (volumetric flow and linear speed). This is about a dynamic phenomena. You basically need to measure the length along the centerline of all your components along the intake path: back of intake valve to manifold mounting surface on the head, outlet to inlet of the manifolds, and outlet of the carbs to the inlet of the air horns. You add all those lengths up and that's your effect intake length with respect to harmonics. From there its a function of the speed of sound in air. You can see how changing the effective intake length shifts the RPMs of the different harmonics. In my case, my intake length was a bit on the short side, adding the 1/2 specers brought the 2nd harmonic to a more usable range.



It's an educated guess based on the combo, especially the heads and cam, but everything counts in its own way.

With this much thought with carbs maybe ninja has it right going with efi.

I already tuned my intake length, Brian it sounds lie you read the same article that I did. I calculated the length based on what the 914 boys are doing then played with the stack lengths till I got the harmonics is a usable range (3000-3500 for me). I had to sacrifice the engine lid to the gods of speed