The heart of the build is the fully counterweighted crankshaft specific to the 2007-2008 Spec V. All the QR25DE Nissan motors received revisions in 2007, new intake manifolds, cams, cylinder heads, balance shafts, etc.

The problem with the old cranks is the half counterweighted design makes the crank unstable around 6900 rpms. All cranks will deflect or flex in the direction the forces from the reciprocating parts (rods and pistons) act on the crank. This is normal, but too much of it is bad as it can cause metal fatigue. Once you make the jump the heavier forged internals the amount of torsional flexing and the resultant torsional vibrations increases. The firing of 1 cylinder every 180* of crank rotation is perfectly timed to induce and magnify 1st and 2nd order vibrations. Hence the reason a lot of 4 cylinder engines have balance shafts. Balance shafts don't rid the motor of vibrations, they simply create vibration timed and tuned to counter the vibration of the motor, making felt vibrations less. Torsional vibrations are dampened by crank pulleys and some flywheels........ hence why I won't run a light weight pulley.

The problem occurs when vibrations against the axis of rotation show up. The single counter weight of the half balanced crank applies an asymmetrical force to counter the weight and forces of the reciprocating parts. As RPM increases so does the asymmetrical counter force. This causes the crank to flex against the axis of rotation , and in doing so it's the main bearings that have to deal with that type of flex. It made short work of destroying the motors team RTR was running in their Spec V cars. They made great power and would rev 8k plus but by the end of each race the bearing and main bearing bores would be beaten out of round and the motors would go in the dumpster at the end of each race weekend.

The New QR motors in the 2007+ Spec V's have a factory redline of 6800, but fuel cut doesn't kick in until 7100 or so. So in a built form should be good for a little more.

The rod to stroke ratio of the QR is the lowest of any motor in production, 1.43 to 1 so the piston speeds at full tilt are close to if not higher than an F1 car, lol. We could have gone with a longer rod and a piston with the pin raised in the body, but it was hard to justify the trouble of spec'ing out that combination. Plus with the improvements of the 2007 factory connecting rods we felt it would be beneficial to see and to show people what a rotating assembly w/ a stock r/s ratio and piston compression height is capable of.

Mike Kojima and JWT are undertaking a similar build with the exception of running a longer rod combination, less aggressive cams and a new 2007 crank, they were running the old crank. I've worked w/ Mike on cooling issues they had early on when the first motor suffered a failure due to overheating. Their motor is WAY more trick than this one because they are Mike Kojima and the JWT crew and have a bigger budget, lol. They managed 490 whp on 15psi w/ a GT30 and race gas on a stock motor (on the dyno only) while tuning the ECU. The GT30 is going to be absolutly maxed out on this build, we could have gone larger, but we want good responce. 15 psi to more than triple stock output is just a testament to how much this motor loves boost.

It's an open deck block but it's nothing like a Honda block. The belife all open deck motors need to be sleeved for big power is left over from teh early days of building Honda motors. Factory Honda Sleeves don't connect to the block untill a good way down so cylinder shift and wandering were common. Also the FRM factory bores in Honda motors don't like to be bored and will crack under pressure, and so started the tuner urban legend all open deck motors need to be sleeved. I don't fresee this being a problem with this motor, even with the open deck design.