Building it right

Building a hybrid takes common sense. We don't want to see you kill/injure yourself in the process or even worse, endanger anyone in the vicinity. 

So, here's the list of what we see as inappropriate for a reliable, daily driven car. 

H22A (Prelude VTEC) in any Civic/CRX/Integra

• The H22A engine leans in the wrong direction

Civic engines have blocks that lean forward while the H22A block leans backwards, towards the firewall. Even though custom fabrication will mount engine, it's still not suitable for this chassis.
• Fabrication issues

Custom fabrication is required to get the H22 engine to fit. The stock motor mounts have to be removed and new mounts relocated, making this an expensive job. Modern day cars are designed from the ground up as an integrated structure, and this includes the engine. Moving mounts around causes the structural characteristics to change. Furthermore, it also increases the chance of a screwup happening.
• Chronic understeer

The heavy load up front will cause tons of understeer. Furthermore, the added power up front will cause the front end to lose traction too easily. What you have is a car that goes fast, only in a straight line.

B18C in 4G Civic/CRX

• Fabrication issues

The engine mounts have to be moved around for this engine to fit. On top of that only 3 of the 4 B-series mounts can be used and it does compromise the engine's rigidity under heavy torque. Then, there's the issue of cost.
• Hood clearance problems

The B18C is a taller engine than the stock D-series motor, and the other B-series motors. Hence, custom fabrication results in the engine hanging too low in order for it to clear the hood. This positions the oil pan and exhaust downpipe lower than the front crossmember.
• Suspension problems

With the low mounted engine the stock suspension's radius rods are about 1/2" from the crank pulley on one side and the transmission housing on the other side. That measurement is at the stock ride height and expect the clearance to be less if the car is lowered. Normal suspension movement in driving will cause the radius rod to hit the pulley or transmission housing. Unless the radius rods are replaced with curved ones, there's no way to protect the engine and suspension from this form of abuse.
• Refer to these pictures to get a better idea

C30/C32 (NSX) in any Civic/CRX/Integra

• Engine is too big

It should be obvious that the engine is way too big. Even if it can be placed in the rear, it doesn't mean that it'll even run.
• Fabrication issues

As with any fabrication issue, the structure of the car is changed radically, especially if the engine is mounted in the rear.