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Thanks for the link. I have a bud that has a flow bench. We'll be pulling some numbers real soon.

Doing the math for the 137 intake flow vs 104 exhaust flow put it at 76%. Not bad for out of the box.
Some bowl blending, port matching and short turn work would do just fine for most builds, imo.

* did some searching about airflow. I've been out of that loop for a long time. Turns out that a street driven vehicle is happy at the low 70% level. The upper end of that chart is the Hi-Perf stuff that likes the 85+ %. Maybe that is where I got that number stuck in my head.

Kinda gives me confidence in the port flow efficiency of the AMC Wasser head. I also crunched some math for CFM at .75 VE using the chart from the Boston Engine link, that I can't seem to now open. Using 5k rpm, airflow at ~.350 lift was 138+/-, so it's all good, for now.

I am of the opinion that a simple bowl clean up and port match will do justice for the engine. Attention to the details goes a long way. Velocity is my goal.
Gotta go find my die grinder, carbides and scrolls.

I got a pair of 2.1 runners and a plenum recently. If I wanted to retain the 1.9 plumbing, it looks fairly easy. The 90* fitting on the right would be cut so it comes out straight. There is an extra tab on the top but does not appear to be in the way of the return spring. The plenum to case mounting tabs look the same between the 1.9 and the 2.1
The left runner has one screw mount and the right side has none. I'm sure that I could machine a slot in the water hose tube bracket and use a hose clamp or something.

Interesting note is that the 1.9 runners are 38mm outside and the 2.1 runners are 40mm outside.
Kinda reminds me of the AC 78 Bus I once owned. The 2.0 runners were pinched down whereas the 2.0 914's were not.
Valve size dictated that of course. Just goes to show that it's the package. It's all in the package.

There is also some mating issues, iirc, with the 1.9 TB to the 2.1 plenum and I should be able to work that out.

I might be able to get away with using all of the 1.9 intake tract parts with little loss of power. Might gain some velocity.
Can't take away from the factory engineering, though.

I'm not looking to re-engineer anything that the factory didn't already do but if I can get another 20 ft/lbs, I'd be happy for this build.

When I get a chance to catch a breath, I'll tear it down for a looksie.

HEY! It's been four years. I finally tore that core dahn. Doesn't look too bad at first. Came apart easily. I did have to make a pin puller but that was easy enough. Bearings look good. Almost like it doesn't have too many miles on 'er. I'll get into it soon enough.
Going to go with GoWesty exhaust, keep the 1.9 intake parts for now although I have 2.1 runners and plenum and keep the 1.9 cooling. I have a 2.1 rear carrier so I'll trim away some sheetmetal.
Cylinders have hardly any ridge. Hard suckers they are. To keep cost down , I'll keep it a 2.1, which is just fine for y style of driving.
I have two cams in mind that are on the lower end of the scale for torque. I'll do some gasket matching and bowl work to the heads and run 'em. I have to determine if the AMC heads have the later better hardware. Otherwise I'll at least change the exhaust valves.
Finally, huh?

Cool.

the bad hardware amcs had seats made from old bean can material, the intakes would even pound into them

I'll have more time this weekend to look things over. Today I looked at the cam gear. I do not see a size number. The cam itself has two raised rings just past the midway point. I'm not going to reuse it however. Rods have a raised bump in the middle of it that seems to be an orientation mark.