| Hi All I been seeing a few people asking about how compression ratio, cams, and for reference I am also including how a valve change would also affect things. I first like to point out compression ratio as I think its one of the most overlooked points in building a motor. The compression ratio of the motor should be matched to needs of the turbo and the cams. For example if you know your turbos are going to efficient at higher Pressure ratios there is no point in going high compression and likewise if get better efficiency at lower pressure ratio maybe small raise in compression would be good. Here is a chart showing how horsepower and torque get affected by changes in compression ratio. This assuming stock environments. 
Now many will say it that ofcourse the compression ratio is going to beneficial this just a case to show it. There are alot of people under the opinion that upgrade cams are going to cause a big loss in the low end power of the car and that not big gains are going to be seen. I tend to disagree with this train of thought and cams available to the 300ZX are actually quite reserved. Here is comparison chart I am using specs close to those of JWT400+ cams which is probably one the best cams out there for the 300ZX for most people anyways. 
And the final chart shows the benefits of going with oversized valves. Now here is an important thing to consider that on a stock bore there is not much deshrouding can be done to truely take advantage of bigger valves. So 1mm OS is about as much I can see feesible on a stock 87-88mm piston. However there are some gains to doing it. Here is a chart to show that please not that HP bar is the same as before. 
And finally here is chart comparing stock to a car with raised compresison, bigger cams, and 1mm OS valves. 
I hope this helps some even if it maybe obvious to others. And for reference these dyno charts don't account for VTC nor for the exact flow pattern of the intake manifold or the exhaust manifolds. So don't take the numbers as expected real world results but more as academic reference.
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Dyno Simulation Stock configuration changes - 
