High Compression 390

the NP 435 is a farm-truck trans. It is a 3 plus granny. And granny is unsynchronized IIRC. I cannot recall that granny ratio but I seem to remember there were a couple available, with ratios between about 5 and 7, to 1, (and I seem to remember one at close to 10/1). In either case, with a 3.55 rear your starter gear is as good as useless at between 16 and 25 to 1, and there is no way to downshift into it. That leaves you with three wide ratio, slow-shifting, high enertia, gears, All suited to a farm-truck or a low-rpm engine. IMO get rid of it.
>At 7000ft and with aluminum heads, you can run almost any Scr and cam you want to, on skunk pee. Just keep the Q in the zone. And I would shoot for high pressure with a cam that suits your application and personal goals.
But
If you run the pressure up,you cannot drive that engine down to sealevel. If you optimize for sealevel, it's gonna be soft at altitude. I'm not saying you cannot drive it down the mountain. I am saying, if the pressure is optimized for 7000ft., then at sealevel, you cannot give her full throttle down there.
And once built,you only have;the ICA to work with, and, if you build it right, the head gasket thickness.
There is about a 30psi change in cylinder pressure between 7000ft and 1000ft.
So it is possible to optimize at 1000ft having a small-cam torque monster,beast of an engine, which at 7000 becomes an average-joe engine.
Or you can set it up with minimum Q at 7000, and maximum Q at 1000, with just a gasket change. 2.5cc doesn't sound like much, but it's still .3 of a point in Scr.
But if the engine will be staying at 7000, and for your stated useage in post #1, then if it was me, I would get the pressure up and probably throw that small carb away.
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My aluminum headed 367 at 10.9 and with a 230*HFT is incredibly docile with a 750DP on it.And once I had the bugs worked out of it, it has never required anything but regular oil-changes. Oh and yes, it still burns 87E10.
If you have to keep that NP trans, You are gonna be starting in second gear about,All the time. You are gonna need torque to get you thru those other wide-ratio gears to top gear. Pressure and cubes are your torque makers. Your 390 will have enough grunt at 7000ft even with pressure down at 160, in which case you could easily run iron closed chamber heads. The question is why would you cheat yourself out of another 25 or 30 psi, if you already have the aluminums?
Jus my opinion