How/why does heavier oil quiet ticking top end?
 

My 2017 Dyna was built a 124 by Hillside Cycles. It has Vulcan Engineering Shaft Lock rocker arm supports which lock the shaft, so no need for rocker lockers or other doo-dads. But with the stupidly high lift Wood 9F cams, my top end was always noisy. Even when new it wasn’t quiet.

Anyway, I always ran Redline 20-50, or 20-60 after moving to this inferno that is SW Florida. But a month ago a friend recommended Amsoil 60w. Which I’ve read isn’t really straight 60w, but more like 30w-60. But honestly it made a difference. Not silent, but an improvement.

So I’m trying to get my head around how oil can make a top end quieter. Any facts on this? Thanks.

Heavier oil leaves a thicker layer on the surfaces that it coats.
This equates to “more oil” on these surfaces compared to what thinner oil provides.

For lack of a better analogy, think of it as a “liquid shim”.

Yes that's what I expected to hear, but I still have a hard time with it, since it can only be slightly thicker when hot then the 20-60 I had in previously. I was thinking maybe the lifters were getting a little weak and the heavier oil was keeping them more pumped up. Or it could all be in my mind. I want to find a good sound recorder (not the crap that comes on phones) because what I hear and what my iphone records are two completely different sounds, and record the "straight" 60w vs the 20-60. I'll be back if I can do that right.

Some time back a guy on a Norton forum built a test rig and tested several different oils to try and identify the best choice for Norton twins. Here's youtube link to his efforts:


No need to watch the whole thing, as I'm pretty sure he didn't mention the 'winners' in the video. I mainly am offering it because it shows how much variation there is among brands that are all 20w50. This was a big learning for me. The first few minutes indicate just how serious an effort he made.
Working from memory, there were several that ranked better than most. Some were brands I had never heard of, but a couple that you can readily source are Castrol 20w50 and Mobil 1 20w50 , both of which are available 'for v-twins'. I could dig back into the forum over there but I think if I posted a link you'd have to join to see anything. If you really want to try and have a look for yourself, it's AccessNorton.com. They argue about oil over there too.

Lifters leak down less.

The thicker the oil is, the more “insulated” the sound.

Deleted…

first you must determine the root cause. a lot of syn oils are rated so as to compare with dino oil but the vis is diff, in the beginning, it used to say protects like so and so weight. that said, lower vis syn oil protects the surface just as well even better. the same with tire ratings, goes back to the clothe type tires.
mr. max makes an excellent point in that lifters can leak by wear and by design. that said, are the lifters matched to the cam profile. the reason i run with solid or near solid setups.
your cam choice plays an important role also, especially with high profile types. when the valve is opened and the the cam lobe passes to the closing phase, due to inertia, the roller might have a slight loft which creates noise.

I'll buy that on a start up condition but wouldn't think a bleed down condition would be happening at sppeed / rpm's

Thanks for the interesting reply. Cams are Wood 9F, which shown are here:
https://cimg9.ibsrv.net/gimg/www.hdf...b2912d2560.jpg

The lifters are also Wood Alpha's. Which are very likely designed to handle his abusive cams. The springs used are Kibble White .660 springs - per the build sheet written by Scott Palmer at Hillside Cycles who built the motor (specs in my sig)

And to add an update. I was never a fan of switching to Amsoil from Redline which I've been using for the last 30 years in everything. So I swapped back to RL 20w-60 this weekend, to make sure I was hearing what I thought I was hearing and not subconsciously hearing less noise because I was "supposed to". But of course, I hear little to no difference. Maybe the amsoil is a little quieter, but not much IMO. I got to get a better video from the same position to be sure.

And listening to them, Redline doesn't sound that bad actually. So this thread was a waste of everyone's time. I apologize for that...

Here is the motor at temp after an hour ride using Amsoil 60w

Here is the motor at temp after an hour ride using Redline 20w-60