tl;dr --
@mdavlee is there
anything you could share/add to this concept that wasn't already explained here? Looks like your~3/4" long Grunt Gasket is relatively straight-shot, am I seeing that accurate or is there some divergence in those walls of the Gasket?
Thanks for any insight you can provide, I'm using a pair of exhaust-ports to make 1 grunt-gasket for my 660, just an easier approach for my tools/experience, at any rate the OEM 660 port is:
0.810" long, and
about 7.5deg divergence (straight/single-angle divergence in that 0.81" long port)
I've got a pair of 660 exhaust-ports I'm using for this, gives me around 1.9" long exhaust tract total (and the pair of them lets me ensure I have a continuously-increasing angle of divergence in the tract), my hang-up is how to look at it, I mean it's basically functioning as exhaust port // header (or lead-in pipe)//divergence cone all at once, and obviously not able to be timed for a sonic return-wave (ie
all of the effect will be from the progressively-wider tract causing 'pull' on the gas and, likely, a "smoother" muffler loop since the cylinder-to-muffler distance is now almost 2" instead of <1"!)
Very interesting. How would a longer exhaust port help. Seems like it must continue opening area which means the muffler needs to be enlarged more?
Even w/o divergence in the port/tract, simply making it >1" long at least lets there be more semblence of pulsing and a true 'exhaust path' (my brain kinda sees it like a sawed-off shotgun, wherein
any additional length is inherently good, whether it's divergent angles or not, simply because the 0.81" OEM exhaust tract is too short for optimal performance)
Did you mill that from solid metal? I'll admit I was thinking that path, as well as simply pouring aluminum to-shape (I have a small kiln, bit PITB!!) until I, thankfully, realized I could just use exhaust-ports from old/wasted cyilnders
Could you stick that torque block or what ever its called on the inside of the muffler to keep everything else from sticking out?
The point of it is to extend distance in-between the jug & muffler-body, so putting it inside the muffler would be self-defeating.
Not without a lot of grinding and welding. Have to shorten the muffler body
Muffler size... On the 660 you can replace that front protrusion piece with a flat steel plate, reducing muffler-belly by like 20% (I wanted to do this just so the muff isn't over-hanging the front of the powerhead, which a 1.25" Grunt Gasket would cause) Uncertain if I wanna do the steel plate (and reduced muff volume) or not, would love if you had any thoughts on this (am also a bit confused why you'd put such a large hole on your muff on the exhaust-path, unless maybe there's a baffle-wall there blocking it or soemthing?)
Thanks for any insight I was so stoked seeing your username when finding this (RARE) mention of Grunt Gaskets!!
