PROPER ENGINE ANGLE
Hello,
First and foremost, the engine/transmission centerline must align exactly with the chassis centerline. Chassis Centerline: is determined by measuring exact center between the main framerails from the front of the chassis to the rear. The crankshaft and transmission output shaft centers must be mounted in the chassis at exact center.
If you are really committed to checking and refitting/fabricating new mounts and motorplates to fix the problem it will require some basic tools and patience and the end result will be a better launching race car. A properly aligned and mounted driveline (engine, trans, driveshaft), this assures safety, performance, and reliabilty of any race car.
One important race car fabrication rules is: higher crankshaft centerlines raise the CG, center of gravity. This increases weight transfer to the rear wheels on acceleration. To some this may sound great but instant weight transfer equals wheel stands which multiplies into lost E.T. Think of an NHRA pro stock car they just squat and go, this is because of ideal CG and weight transfer. There is no real set formula for ideal crankshaft centerline height because there are too many factors in many types of race cars but between 9"-12" from the race track surface is found to be most suitable, depending on the chassis design this can have some limiting factors when considering suspension mounts and steering mechanisms.
In most tube chassis race cars, level mounting of the engine/trans assembly will almost always leave the transmission output shaft too low.
This causes the installed driveshaft to operate the universal joints at angles. Most would say, isn't that what u-joints are for? Yes, the design inherantly takes up miss alignment and angle but this is applicable in passenger vehicles and trucks. Angular operation of u-joints in a drag race car application causes a non-constant turning velocity of the driveshaft. The result can be driveline vibration, stress and power loss.
Most professionally built race cars actually have an engine angle of 1-2 degrees, meaning the tailshaft or the transmission output is actually angled upward which aims the transmission outputshaft directly at the rear end drive pinion.
The correct angle is determined after the engine crankshaft centerline height is determined (crankshaft centerline height from race track surface). Once the crankshaft centerline height is set you will determine the correct angle by pulling a string or light guage wire from the front of the crankshaft snout centerline to the rear end drive pinion. Measure the angle with a protractor (angle finder). This process is usually performed with a "dummy" engine block installed in the frame rails without a transmission bolted on and a wood or aluminum puck installed in the #1 main saddle of the engine block. A small hole is drilled in the center of the #1 main puck to feed a string through. After the angle is determined, bolt on your transmission and raise the engine/transmission angle until you reach your determined angle. BE SURE TO MAINTAIN THE ORIGINAL CRANKSHAFT CENTERLINE HEIGHT DISTANCE AT THE FRONT OF THE ENGINE. You will only be physically raising the rear of the transmission output shaft to meet the desired angle. After the engine/trans is mocked-up at the correct angle then you will proceed with making new mounts and motorplates.