Yeah, I kinda figured that out.. Mildly acidic is OK. Vinegar works OK but the phosphoric acid does better..

 

In regards to the intake spacer topic.. it’s not as much about flow adding or deleting length. It’s more about cam to valve timing. Figuring out the right length can greatly aid valve overlap to make more power at higher rpm’s. Couple it with tuned exhaust (length) and for scavenging and sonic pulses and it really does make a difference. There are mathematical formulas that are close and get you in the ball Park. When it’s right you’ll know it. You’ll feel it. It just flat grows legs on the top end like you hit a subtle bottle

 

HD V twins like a longer intake on a carbed bike, older ones in particular. Heard and read a lot science behind it, just know they do. I add a 1" spacer with the the Super E and there's a noticeable difference on my 93" shovel in streetability.

 

So how much length did you add to get the hit? 1 inch? 2? 6? For sure simply adding spacers won't increase flow. In fact it will like decrease it. It can increase velocity.

 

That changes with cam cubes and compression, rpm. My 93” is heat (just shy of 1/4”) 1” (heat shy of 1/4”) 3/4” Carb G. The intake I blend all assembled together with a cartridge roll. I don’t like it polished, just textured and blend together. The S&S cover is cut back 1” and that counts in the equation. I could go back through my notes but I “think” that was like the 4 or 5th pulse I matched up to with that cam. I ran several cams but kept coming back to the M grind. The 119 bandit cam was amazing but say good by to your heads, guides and springs cause it brings havoc. To set the 119 or my vthunder 630 cam I had to sink the valves 30 thou and to get compression where I wanted I had to go to a taller dome and dual plugs..in the end just not worth it.

one of the combos at 13:1 with the bandit cam I used a angled 4 5/8 elbow with a 1” spacer. So it changes with your combo.

Flow… velocity..? Lol Shovels.. beloved Shovel suck, those massive hemi chambers are never gonna be efficient. (Relative term) so you use more compression, obnoxious lift, lots of rpm to jam/ram as much of that angry temperamental mix through there and you keep your rpm’s up where your scared and the guy in the lane beside you is even more terrified from that noise his rubber mounted Twinkie has never made. I’m just learning and my journey really is just beginning with EVO so I’m not sure what’s applicable and what isn’t.. but I personally believe in the shovel world valve overlap is your secret compromise weapon.

 

So you added 5 5/8 inches to the intake? And ran it without so you could compare..

 

I see the spacer as being no different than adding a 1" spacer under a carb on a car engine, it increases what plenum volume is there even if it's what you would consider a very small plenum.

 

lol yep.. and lots of other combinations.

Side note.. How I tune drag pipes is to start at 40”.. cut an inch run two passes.. cut an inch run two passes cut an inch run two passes….. I did that until Mph averages went up.. then I kept doing it until it went down. Then I took a new set of 40” and cut one Inc longer then the experimental pipes. I use to have 3 sets I kept at different lengths to get as close as possible… here’s the kicker, change compression, cams.. start over. Edgwater, Dragway 42, KilKare were favorites around 2002-2003.

Now don’t be to hard on me.. years ago, nobody to help or learn from. Those days I was flyin blind with nothing but an empty wallet a local track and a few books.
‘Here’s some notes from way back on intake pulses and rpm’s based on a 11.7:1 93” and a M grind cam. 5300 rpm was used because that was right in the middle of my power band between shifts. As you can see I intentionally over shot the power where most would with that cam. I did this on purpose because of my torque curve and using 3 gears in the quarter.

 

from the back of the valve to when it hits the atmosphere.. that length can be tuned to take advantage of those pulses at a given rpm. True of intake, true of exhaust.

 

The main thing that you are missing is that a car has a plenum, the HD does not..