Plenum effect is back, if I move the box around over the thing running the vacuum moves up and down, so the effect helps when it crowds the intake a little.

So through the std 40.5mm 152cfm ,about, and 157.3 through the seat opened to the 42mm valve, both with the 34mm carb. If my base calculation is correct. So a stock valve with 34mm carb should perform really well with this port and I will do a head.

I cannot do the 42mm seat properly without the proper guide fitted and K-lined which is annoying. I cut it so I could mark it with blue, but hopefully will be close. The worst thing on these is an automotive cutter to cut 3 angles at once, as the hemi insert then gets cut in with a step to get a top cut, the deeper the worse.

The plenum effect gives 171 with no carb and radiused entry. I guess the more it reads whatever it actually is the better. And it reads consistently and the comparison is good. But now is pulsing a bit. And higher lift is worse than .350" it makes more noise at .388" but doesn't flow more. so maybe the air is leaving an edge and breaking up at higher speed, and its faster but blocked by some turbulence?

Through the carbs it's at least + 45% on stock. I'll take some photos when I change it over for the other side.

These little welded manifolds are round 34mm tube squashed at the head end to be 30mm high and whatever wide the threads are helicoiled to smaller dia for these screws to fit.
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They are within 2cfm and one is better further open for some reason. One side broke into a valve spring recess frown so a patch. The SRM race springs fit shorter so a washer can protect the little patch.