which of these two engines would be better 86-88TII or 89-91TII??? im wondering because obviouslt the newer ones have more hp/tq but it also has higher compression and in piston engines when people are going to have alot of boost the switch to lower compresion pistons so am i correct that the older ones would be better???

 

yes 88 has lower compression, but how much boost do you plan on running......90 rotors and flywheel is lighter meaning rev happy motor....like a 93, rotors are the same, but flywheel is lighter.......point i'm trying to make is that if you're not going to run a rediculous amount of boost you don't need to use 88 motor.

 

yea see i want to get a newer one but i may get a 88 AE thats is totaled but are thew older ones still good and worth working on

 

The s5's flywheel Is 15% lighter than the s4 one.

 

soooo if i bought a flywheel this would solve that problem??

 

The rotors and main internal parts of a s4 can be reliable to any number you want pretty much. For high RPM (boosted) use the same clearancing, balancing, & and upgraded internal parts (oiling system, bearings, etc.) need to be considered. Other than that there is no problem, with it's ability to handle huge power.

Most serious builders tend to use 9:1 rotors because they are lighter, better machined, and can handle great power on pump gas. Why use a lower CR?

If you have a good S4 motor, I would not worry about the 9:1 rotors. If you are replacing the rotors anyways, go with 9:1. My personal preference.