An important part of planning modifications to an engine is to determine a theoretical limit of power for a given combination. It's good to have some idea of what the thing might be capable of before spending a lot of money. In this document, I’ll try to provide some examples and tools which will show you how to do that.
Note the word theoretical. In this case, that means that results are going to be close to the real maximum in almost every case, but that cannot be guaranteed. Each dyno, flow-bench, and ported head is different. Each operator can affect results. Environmental conditions can change, which will also alter results. Even on the same dyno, run-to-run variations can be as much as 1 or 2 percent. There are no guarantees.
All head flow figures are actual figures from porting facilities, quoted at 28” of water. Where the originals were at 10, they have been up-converted to 28. This will introduce a small error in flow, but should not substantially affect results.
All examples assume adequate exhaust flow, but do not incorporate any potential increase in power from exhaust tuning. Air Fuel Ratios are assumed to be correct for max power for that combination, the cam is assumed to be ideal, ignition timing is assumed to be correct, etc.
In other words, the idea is to objectively estimate the maximum horsepower the heads, induction system, fuel pump and injectors are capable of.
You may have seen the phrase “It’s Only Air and Fuel” before. One of my friends used to wear that phrase on T-Shirts at events where he had set up his dyno. Or you may have heard of an aftermarket Fuel Injection Controller company named “F.A.S.T.”, which stands for “Fuel Air Spark Technology” (or is it "Timing"?: Either way, the point remains).
The point of this is that power is a result of the proper ratio of fuel and air delivered to a cylinder, with an appropriate spark delivered at the proper time. Fuel, Air, Spark. That’s really all there is to it. Everything else is intended to supply, regulate, or contain those things.