75 CB360 - bad omen "yatagarasu" build

[MiniatureNinja]

How in the hell did you get your engine covers looking like that?!  Really nice work!

Lol, I was amazed myself.
Sanding by hand, first with red scotchbrite pad, then 400grit sandpaper, then 600. Then 1000. Then polishing wheel on 8" buffer using semichrome aluminum polish then smaller loose wheel. It's not as good as some I've seen. But ok.

Also. Ports. Feedback? Still got time to make better if needed

[Sonreir]

Looks good to me. Put on the rubber intake manifolds and try to match the lip, too.

[MiniatureNinja]

Looks good to me. Put on the rubber intake manifolds and try to match the lip, too.

Most definitely!


also, anyone know where I can get these:
https://www.cmsnl.com/products/cap-tappet-adjuster_12361rrp010/


in the US?

[teazer]

That could use a slight clean up.  The guide bosses could also be slimmed a little but keep the olive shape so that gas will flow easily past the obstruction.   try not to open up the exhaust and don't remove that step in the floor.  It will act as somewhat of an anti reversion dam.

But you get most out of porting from the 1/2 inch to an inch past the valve seat.  You need a venturi shape and smooth transition.  You will probably find that both ports are restricted around the guide and valve and at the point the short turn radius should be as smooth as possible and raise the roof to get the appropriate area.  Do not drop the floors - they are already too low for good flow.

And do NOT polish the intake - it hurts power because fuel drops out of suspension and won't burn properly

[MiniatureNinja]

That could use a slight clean up.  The guide bosses could also be slimmed a little but keep the olive shape so that gas will flow easily past the obstruction.   try not to open up the exhaust and don't remove that step in the floor.  It will act as somewhat of an anti reversion dam.

But you get most out of porting from the 1/2 inch to an inch past the valve seat.  You need a venturi shape and smooth transition.  You will probably find that both ports are restricted around the guide and valve and at the point the short turn radius should be as smooth as possible and raise the roof to get the appropriate area.  Do not drop the floors - they are already too low for good flow.

And do NOT polish the intake - it hurts power because fuel drops out of suspension and won't burn properly

thanks,  what do you mean by olive shape? don't "triangle" them off? I remember from a couple other threads not to go anywhere near the floor of exhausts. I did make sure I smoothed off the radius so it wasn't a "sharp turn" without dropping it
Here is where I know more harm than good can easily be done so I did my best to retain shape and size, only matching the intakes with the boots, the exhausts with the gaskets (except the bottom part) and smooth the transition in the seat area where the casting goes against the seat, made it all nice and neat and a smooth flow.

I only kind of understand the theory of port shape and size, I don't know enough algebra to assume that I am a better port designer than Honda was (even in the 70s) so I figured it best to not reshape even in the roof area. I know that the ports get wider in the area of the guide boss as air can get squished in there - I just knocked back all the casting lines and a few imperfections. This head was actually pretty good, not like some cast ones I have seen inside it looks like a huge thick flashing, this was even barely noticeable

[crazypj]

Leave guide bosses 'rounded' but narrow them down on valve head side of guide. If you have a 'radius' around guide flow will be better than step. On exhaust you can change the  'lead in' a little more, I like to reduce angle of the 'hump' just before exit (gas is hot and dry  so may not actually do any good?
 I tend to make 'flow diverters' by making sides of  bosses concave  (triangular) but it does increase post volume so you loose a little bottom end.

[teazer]

The reason that ports get wider at the restriction is to try to keep the cross sectional area up without dropping the floor or breaking through into the valve seat pockets when the roof is raised too much.

I used teh word "olive" to describe the current shape of the guide boss.  It gets wider and then narrower as it approached the guide, that helps flow to go out and them come back around the valve stem.  If it was a straight triangle shape the gas would continue to flow "out" away from the valve as it passes it and that would reduce flow.

One issue with our old heads is that the ports are low with tight radius bends and that hurts flow compared to a modern motor with very steep down draft intake ports.

AG Bell in his book on Performance for 4 strokes has the whole intake port mapped out and so do some of David Vizard's texts.

On the intake we tend to open up the apparent restriction just below the seat and unfortunately that cuts flow by directing it at the valve head instead of around it. That's why there's a radius to get the flow around the valve when it's opening.

https://www.google.com/search?q=4+stroke+venturi+port+vizard&client=firefox-b-1&tbm=isch&source=iu&ictx=1&fir=NUJ2dqkXybMikM%253A%252CGAUDPSbsruuSPM%252C_&usg=__3jV63e6IpKyKhbJu6243u-c27p0%3D&sa=X&ved=0ahUKEwjSxoyIo4jbAhXJq1QKHTgRD5YQ9QEIKTAA#imgrc=_

[crazypj]

Quite often I've deepened the 'pocket' on the long side to direct flow around valve head instead of into it. It's often necessary to do so to get venturi 'correct' below valve head, particularly when 'short turn' is a real bad shape (as on 360's or Iron Head Sportsters)

[MiniatureNinja]

Working away late into the night, someone asked me how much per ounce I've spent making this bike lighter.... what a stupid question,  now I'm depressed

[teazer]

Add lightness.  That's how we improve power to weight ratio.  Holes are good.  Replacing steel with aluminum is good, using Titanium is nuts unless people can see it and admire your excellent tastes and previously deep pockets.