building a 13-REW with streetport at the moment. would you recommend using S4 8.5:1 rotors in the engine instead of the higher compression FD rotors?

I would.

that's what i'm using.



along with a renesis e-shaft and stationaries, and a cosmo intermediate.



i've got one bastardised motor!

It's not a bad idea even though those rotors are heavier, but I would admonish you to remember to also use a Series 4 front counterweight w/ S4 flywheel or aftermarket flywheel w/ S4 rear (balancing) counterweight. Otherwise, it will throw the motor dramatically off-balance and quickly lead to the engine's destruction (among other things).



B

Yep, and also keep FD front bearing/thrust stack especially with an aftermarket pull style clutch..

thanks you for the replies. did some further searching and reading on the subject.



another thing about balancing: i guess i don't have to balance the internals because i stay under 8k rpm with a streetport but what's the story with a 1/2 bp since the power is more in the upper regions (with REW engine and S4 rotors)? how high will a 1/2 bp rev to make top power when thinking about a big bridge and is balancing a must?