Get your minds out of the gutter! What is required to increase the rpm range on say a 2.0 block? Springs? Springs and valves? Cams? I am not looking to do a port and polish or make high power. Just looking to rev to 8-8.5k on a small displacement engine. ssh:
Springs are required Valves are usually just stronger to support the increased seat pressure and abuse that come from a high revving valve train. Cams are not required, but they are literally just windows (opening and closing) just depends on where and how long you want that window open during your combustion cycle/ rev range. If you are autocrossing or something and want to maintain a gear safely through and don't need the power up that high, springs are fine. If you are drag racing and want to pull through the whole power band some additional breathe would be necessary (cams) Edit: old 2.0 had cranks with poor oiling, newer ones are crossdrilled and feed bearing better for higher revs. Also older 2.0 were prone to spine bearings due to tight clearances. This all really depends on what you are doing / using it for. reliably, to make power, or just the occasional over rev Bowl blends to the ports make the best gains on stock heads. Larger valves are an option but are unwarranted on subarus.
Forged pistons Block reinforcement ribs stiffer lighter valvetrain and AVCS arent those the only differences valvetrain being the only requirement to rev higher.
It would help to understand your objectives a little better; sounds like since you are ruling out ultimate power as an objective, [assuming as light the coupe is, this would fit in] , so would this say, be oriented toward "fun to drive and a sound great" as overarching objectives? Is there an existing JDM spec 2.0 engine that would be a starting point? What would the power/torque curve look like to meet your objectives? [Wife's car has 8500 rpm redline, which I generally hit as the 2ZZ-GE only has 180 hp/VVTi, however the nice rev range makes up for the relative lack of power in addressing the fun category for the Matrix XRS] [Wish we had put on the optional TRD Supercharger to get it to 225 hp]
Basically the only thing that both the heads share are the casting minus the intake ports and AVCS depending on what version 207 you get. I have a JDM Ver. 5 207 (non AVCS) and it is basically the same as the USDM 205 minus the intake ports, valvetrain, cams, combustion chamber, etc... All the things that it takes to rev to 8k+ and make power up there (depending on your turbo).
There is no point in revving out an engine unless you are gonna put on a turbo that can supply the demand that high in the power band. Most your basic turbos fall off very hard after 6k rpms. Just throwing that bone out there.
If the application is autox or other low speed racing there is a point it. Most of the driving is done is 2nd gear. So you can rev to 8500 you are able to stay in 2nd longer even if you arent getting much power. Because the amount of time it takes to shift negates any gain you get from shifting in most cases. So if you are able to rev out higher you dont have to shift. My rule of thumb if I hit the rev limiter 4 times I should have shifted, however my car (2014 STi) running on 18s maxes out at about 62mph @ 6500 ish in 2nd. If I could rev to say 8500 I'd be closer to 70 which would be preferable even if I lost some power.
Over all goal would be use the car mainly for fun in the mountains/autox/some track days. This will be going in the coupe which is already stripped out with a lot of weight reduction. The car will also get a cage sometime next year so I can participate in the "Chasing the Dragon Hillclimb" event. I'd most likely go with an hta68 eventually. For starters though I have a td04 with EWG ready to go. Keeping my eye out for a vf series turbo though if a good deal pops up. This. I still want to pick up a 4.44 transmission (I need to bite the bullet on Corey's :keke so being able to rev higher would make up for the shorter gears. I have always wanted a 207 swap, I think I will go that route instead of build a 205. I'd rather buy an oem built motor than try and have one built when there is so much that can go wrong and all of the $$$$ for parts and labor. Plus sticking with an oem engine wont throw me in any ridiculous classes when I decide to do SCCA/NASA events. I will assemble my current 205 for the next year and start looking for a 207. THANK YOU ALL FOR YOUR INPUT.