boost pressure?

I know in one twin-spin 301 A-C Puller, 100 psi intake boost relates to near 1000 flywheel HP on the dyno. By that math, 30 psi would be 300 HP. This is only a theoretical calculation and your results may be different. Seems like a 7020 tractor was around 18-20 psi making 120 PTO HP which would be 145 flywheel HP.

Here's the quick and dirty of it. Your engine doubles for every atmosphere of boost. So if you have 80 HP naturally aspirated, with 15 psi you have 160, with 30 psi you should see about 240 HP. Now there's thermal inefficiency because you heat the intake air with a turbo and some other factors to subtract. Then come changes in can and cylinder head, fuel system etc.

So the engine pushing 7 atmospheres boost (approx 100psi) making 1000 HP has had to have some other modifications of course, but is limited by its cylinder head. Another engine with a better cylinder head pushing 100 psi may make 1300 a d yet another of that size could make 1800. The 301 heads just aren't great for making big HP, but the cylinders are small, a d they like rpm.