STOCK 280 ZX ENGINE POSITION
The stock ZX has the crankshaft centerline at about the top of the frame rail at the front of the engine (crankshaft pulley). The ZX engine/transmission makes about a 1.5° angle compared to the door-sill angle.
The centerline of the front of the driveshaft runs about 4" below the top of shifter hole in the transmission tunnel.
The stock crankshaft centerline of the ZX engine is offset towards the passenger side about 1/2" to 3/4".
V8 MOTOR MOUNTS AND ENGINE POSITION
The V8 should be installed to keep the crankshaft centerline, and driveline angles close to stock to reduce vibration problems, but some variations from stock will not normally cause problems, and adjustments can be made to change driveline angles to reduce vibrations.
In order to keep the front of the engine low enough to maintain stock crankshaft centerline and driveline angles, the Chevrolet oil pan may need to be hammered in about 1/2" where it goes over the steering rack. The amount of modification to the oil pan can vary, depending on how much the engine is moved rearward, and what type of oil pan is used. The more the engine is moved rearward, the less the oil pan has to be modified.
An additional advantage to keeping the front of the V8 engine low is that it improves transmission tunnel clearance, while maintaining stock driveline angles.
MOTORSPORTS MOTOR MOUNTS
In the past, the most common V8 mounting kit for the ZX V8 swap has been the Motorsports ZX V8 kit. Motorsports is a good, reputable, company which offers good products for Datsun Z and ZX parts. Motorsports, however, does not specialize in engine swaps. The motor mounts sold by Motorsports were designed to install the V8 engine into the ZX with minimal modifications to the ZX and the V8 engine. Initially, this may seem like a good idea, but this compromises the finished installation.
Basically, the Motorsports V8 mounting kit positions the Chevrolet engine mounting pads directly over the Datsun ZX’s engine mounting points on the front cross member. We call this position the "zero setback" position. The Motorsports mounts offset the engine about 1/2" towards the passenger’s side.
The Motorsports V8 mounts use the stock 280ZX rubber isolators. We feel these are too soft for the V8, and allow too much engine movement. We recommend using Chevrolet style engine mounts, which are stiffer and stronger than the ZX mounts.
The Motorsports mounts position the front of the engine about 1/2" higher than the Stealth mounts to allow the oil pan to clear the steering rack without modifications. The angular difference of raising the mounts 1/2" is about 1° — not a lot. But when running a carbureted engine, 1/2" can cause hood clearance problems.
The biggest criticism of the Motorsports kit is the transmission mount. To minimize transmission tunnel modifications, the Motorsports transmission cross member positions the transmission output shaft about 1" lower than stock. This also causes the front of the relatively short driveshaft to be 1" lower than stock.
The result of the higher engine position and the lower transmission position combined with a short driveshaft, are driveline angles that are more than 4° different than stock at the front u-joint. While not considered excessive, this can lead to driveline vibrations, and excessive wear of driveline parts, as well as interior parts that fail due to vibrations.
TRANSMISSION TUNNEL MODIFICATIONS
The biggest reason to modify the transmission tunnel, and remove the stock ZX transmission mounting brackets is to raise the Chevrolet transmission high enough to maintain stock driveline angles, and to reduce driveline vibrations to a minimum.
The biggest reason to move the engine rearward is so the shifter of a Camaro 5-speed or 6-speed transmission comes out of the stock shifter hole, in order to reduce visible interior modifications.
The amount the engine can be moved rearward depends on which exhaust manifolds (or headers) are used, and if a rear mounted distributor is used. For example, 1992-1997 LT1 engines do not have a rear mounted distributor, and LT1 engines can be moved rearward without having to modify the hood-latch mechanism.
When moving the engine rearward more than 1", the bolts that attach the bellhousing to the engine contact the passenger’s side of the fire wall. To make clearance for moving the engine rearward more than 1", the firewall/transmission tunnel will have to be hammered in. The modifications are not visible inside the car.
STEALTH CONVERSIONS MOUNTS
Because of the different steering systems (non-assisted rack and pinion, power assisted recirculating ball, and power-assisted rack and pinion steering), the Stealth Conversion motor mounts allow adjusting the position of the engine front-to-back and side-to-side. In addition, the height of the engine can be adjusted by installing spacers between the engine and the motor mounts.
Depending on the engine accessories and the transmission being used, the engine position can vary — and this also depends on how much effort and modifications the owner is willing to do to complete the swap.
The Stealth Conversion’s mounts allow offsetting the engine from 0 to 1" towards the passenger’s side to accommodate different engine/transmission and header configurations. Offsetting the engine 1" to the passenger’s side will not cause any driveline alignment problems. Ideally, the transmission’s output shaft should be directly in line with the pinion shaft in the differential, but as mentioned, the alignment can be slightly offset or cockeyed without causing any vibration problems.
Often, driveline vibration problems are caused by stiff or worn-out transmission mounts. Because the ZX is a unibody, aftermarket transmission mounts often cause vibration problems because they are too stiff. Polyurethane transmission mounts should not be used in the V8 ZX. A soft transmission mount will isolate normal driveline vibrations from the passenger compartment. The stiffness of the motor mounts do not seem to be that critical in reducing vibrations in the passenger compartment, but we still prefer the rubber engine mounts instead of the urethane engine mounts.
The steel needed for the brackets and spacers can be found at most steel yards (look in the Yellow Pages under “Steel”). Metal fabrication shops also carry steel. Stealth Conversions can supply the brackets and spacers. Prices are in the back of the manual.
Motor Mounts: Use Chevrolet mounts that came on 1982-1993 S10 trucks with the 2.8 V6, and 1982-1992 Camaro’s with the V6. Similar mounts also came on 1985-2004 Astro Vans with the 4.3 V6. These are a very common clamshell style which is strong and compact. The mounts are very expensive when purchased from Chevrolet, but aftermarket versions are very inexpensive, commonly under $30/pair.
Transmission Mount: Use Chevrolet factory transmission mount that comes on the Chevrolet transmission.
Use only genuine Chevrolet transmission mounts because aftermarket replacement transmission mounts may use a stiffer rubber, and this may transmit a lot of noise and vibration into the car.