Originally Posted by aaronc7
great thread....yeah sorta bumping it here sorry.
Can we get some info in here regarding what's needed to make the engine last and make power up to lets say... 8k rpm?
These numbers will sound conservative, but I am a track junkie and my cars see more abuse in a single 20 minute session than your average street car sees in a month of commutes. You can probably exceed these numbers in a street car and be OK in the short term, but if you want long term reliability or track reliability, I'd stick to my numbers.
Stock engine is basically safe to 200whp and ~7500rpm.
Folks start to bend rods in the 250whp range. M-Tuned rods are the fix.
Past 300whp, you'll start to see issues in the cast pistons. Supertech pistons are a no-brainers.
300whp/8000rpm is the generally accepted limit of the stock oil pump gears. Billet gears are available from Boundary Engineering.
350-400whp, OEM main bolts are dubious. Upgrade to ARP main studs and use an MBSP if you intend on pressing past the 350whp mark.
Crank and block limits are unknown, but both are higher than 500-600whp. The next power limit is likely the OEM cast main caps, at somewhere around 500whp. Someone else can find that out
Limit of the stock head studs is unknown, probably because EVERYONE upgrades them. You should probably just upgrade them and avoid becoming the guinea pig on that one.
Stock rods will not accept anything past about 7800rpm without stretching. Spec Miatas are documented to stretch rods on single sub-8000rpm overrevs. If you push past 7500 on a regular basis, you need forged rods.
Stock oil pump gears have a generally accepted limit of 8000rpm due to crank harmonics. Push past that (or run at 8k for a long time) and billet gears are strongly recommended.
OEM valvetrain is good up to the ~7800rpm mark. At a certain point, the valves will start to float, which means you either need stiffer springs or lighter retainers.
Making power at 8000rpm is hard. You need a huge centrifugal blower, a lot of port work, big cams, or a combination of at least two of those things. Most people do not spin the motor this hard.
FOOTNOTE: VVT users MUST adhere to a strict 7400rpm limit due to an intake cam harmonic. Change the intake cam and you may press past that limit.