Datsun 280ZX V8 Motor and Transmission Mounting Kit

Why You Might Want One.  Unlike the most common V8 mounting kit for the ZX V8 swap, ours was not designed to install the V8 engine into the ZX with minimal modifications to the ZX and the V8 engine, which compromises the finished installation. 

By swapping out the stock ZX transmission mounts, engine mounts, and rubber isolators and specifying small modifications to the ZX firewall/transmission tunnel, the Stealth Conversion kit reduces driveline vibrations and allows the shifter to come out of the stock shifting hole, reducing visible interior modifications.

Our kit includes engine mounts, rubber isolators, transmission crossmember, and installation hardware. See installation guide for more detail.

Installation. 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 that 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 also use the stock 280ZX rubber isolators. We feel these are too soft for the V8, and allow too much engine movement. We use 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 keep 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.

ADJUSTMENTS OF OUR 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 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.

MOUNTING KIT — TRANSMISSION CROSSMEMBER ASSEMBLY
The transmission cross member assembly for the V8 swap consists of:

• a bracket that bolts to the driver's side of the transmission tunnel (six side bolts)
• a bracket that bolts to the passenger’s side of the transmission tunnel (five side bolts)
• a cross member that bolts to the side brackets.

The installation of our transmission cross member for the ZX V8 swap normally takes a few hours. The original brackets in the transmission tunnel must be removed, and this takes some time. The brackets can be removed with a Sawzall, a grinder, or a plasma cutter.

The carpeting along the transmission tunnel must be temporarily moved out of the way to install the brackets that bolt to the sides of the transmission tunnel.

Five holes must be drilled on passenger’s side of the transmission tunnel to bolt the brackets to the transmission tunnel and six holes must be drilled on the driver’s side.

The mounting kit does not include the Chevrolet style transmission mount because this comes with most transmissions. The stock transmission mounts are usually best — the soft rubber reduces vibrations.

ENGINE POSITIONS

Forward Position. The top photograph above shows the engine moved forward (Zero setback). The distributor is about 2-1/2" from the firewall. The firewall can remain stock, and transmission tunnel mods are minimized. With the engine moved forward, stock 1982-1992 Camaro manifolds can be used.

Rearward Position.  If you are using a Camaro T5 transmission, and you want to minimize shifter hole modifications, the engine must be moved rearward. The lower photo shows the engine moved rearward, so that the distributor is within 1" of the firewall. This requires modifying the hood latch bracket so the distributor can fit underneath. In addition, the transmission tunnel/firewall also needs to be hammered to make room for the transmission — it is a lot of work, but the modifications are not noticeable inside the car.

With the engine moved this far rearward, the Camaro TBI exhaust manifold cannot be used on the passenger’s side.

(Note: The Motorsports motor mounts place the engine in the forward position (Zero setback), but because the front of the engine is high, and the rear of the engine is low (compared to the Stealth Conversion’s mounts), the distributor leans back into the firewall, giving the illusion the engine is positioned more rearward).

WITH PREP OUT OF THE WAY, BEGIN THE INSTALLATION
Remove the stock Datsun Z mount from the cross member, using a 14 mm socket.
Keep the heavy-duty washer — it will be used with the V8 mounts.


Drill a 7/16" hole 13/16" (.81") below the lower hole, and about 1/8" forward.

If you want to increase the range of adjustment for moving the engine forward or rearward, the lower hole can be slotted as shown by the oval.

TRIANGULAR ADAPTER BRACKET

Bolt the triangular adapter bracket to the ZX cross member using a 3/8" x 1-1/4" bolt. Use the original ZX heavy-duty washer underneath the cross member.

Do not tighten the bolt at this time.

WRENCHES

To tighten the center bolt on the triangular adapter bracket after the motor mount is in place, use a 9/16" tappet wrench to fit between the triangular adapter bracket and the Chevrolet motor mounts.

The tappet wrench shown is a Craftsman brand, which is available at most Sear’s stores.

INSTALLED MOUNT

Bolt the Chevrolet engine mount to the triangular adapter bracket using 3/8" x 1-1/4" bolts as shown. Do not tighten the bolts at this time. No washers are needed.

ENGINE MOUNTS

The engine mounts bolt to the engine as shown above, using 3/8-16 x 1" long bolts. Driver’s side shown.

INSTALLING ENGINE
After placing the engine into the car, install the 7/16" x 5" long bolts through the motor mounts.

Make sure the 7/16" long bolts are parallel to the engine. Rotate the triangular adapter brackets as necessary, so that the 7/16" bolts are parallel to the engine. Tighten all the mounting bolts to the triangular adapter pad. It will normally be necessary to use a thin, open-ended "tappet" 9/16" wrench to fit between the bottom of the motor mount and the triangular adapter brackets. 

After positioning the engine for your application, tighten all the bolts. The passenger side will look like the photo below.

ENGINE MOUNT/MECHANICAL FUEL PUMP
If your engine has a mechanical fuel pump, the engine can only be set back (moved rearward) about 1/2". If you remove a section of the mechanical fuel pump (and cover the opening with a fuel-pump block-off plate), as shown above, the engine can be set back 1-1/2".

For further fore-aft engine adjustment, the 3/8" hole drilled into the front cross member can be slotted fore-aft as shown.

MOTOR MOUNT MODIFICATION

The Chevrolet motor mount (or aftermarket replacement mount), must be modified slightly to allow for maximum side-to-side adjustment. Remove the section shown with a hacksaw, band saw, sawzall, or grinder. This will not affect the strength of the mount. For most people, it is probably easiest to use a grinder.

When purchasing the mounting kit from Stealth Conversions, the mounts are already modified. (This note is put here in case the mounts have to be replaced, or are replaced with polyurethane mounts.)

INSTALLING THE CROSSMEMBER

To install the transmission cross member, it should first be assembled as shown to properly position the cross member assembly into the transmission tunnel.

Install the assembled transmission cross member into the transmission tunnel, and mark the positions of the holes.

Drill 11/32" holes into the transmission tunnel.

Bolt the side brackets to the transmission tunnel with 5/16" x 1" long bolts and locking nuts.

TRANSMISSION CROSSMEMBER SIDE BRACKET INSTALLATION

The top of the transmission tunnel bracket on the driver’s side should be at the same height as the stock bracket, as shown by the bold line above.

The Stealth bracket will lay against the stock bracket, taking advantage of the double thick sheet metal on the rear edge of the stock bracket.


After installing the side brackets to the transmission tunnel, lay the cross member on top of the side brackets as shown above, and verify that the brackets are angled properly so the cross member sits level on the ears.

BRACKET ADJUSTMENTS

If the ears of the side brackets need "adjusting" to fit level to the cross member, use a large wrench as shown to bend the ears.If you don’t have a large wrench, the ears can be "adjusted" with a hammer.

TRANSMISSION CROSSMEMBER, TURBO-350 TRANSMISSION

Above we're using a cross member sold by Motorsports. It is shown with a Turbo-350 transmission. The cross member is designed for minimal transmission tunnel modifications when using the 700-R4 transmission.

The Motorsports V8 mounting kit uses the ZX brackets, but these don’t allow moving the engine rearward, and these mounts also position the rear of the transmission too low, affecting driveline angles.

The basic problem with the Motorsports transmission cross member is that it places the rear of the transmission too low. When using the Turbo-350 Transmission, this is easily corrected by installing spacers to raise the transmission (as shown).

The Motorsports cross member does not work well with the 700-R4 (or 4L60-E) transmission.

The transmission tunnel needs to be widened in order to raise the 700-R4 transmission high enough to allow stock driveline angles, and the ZX transmission tunnel brackets need to be cut along the dotted line as shown above.

TURB0 350 TRANSMISSION
If you want to install a Turbo 350 Transmission, an extension plate is necessary that extends the mounting points of the Turbo 350 rearward by about 2". This is available from Stealth Conversions. Motorsports also offers an extension plate for the Turbo 350 transmission.

TRANSMISSION MOUNTING, CAMARO T5 TRANSMISSION

As shown be below, the Camaro T5 transmission requires the ear (arrow) on the transmission tunnel to be removed to position the transmission for the shift lever to come out of the stock shifter hole.

This is the Stealth Conversion’s cross member used with the Camaro T5 transmission. The stock brackets attached to the ZX transmission tunnel were removed to provide clearance for the T5 transmission. (above)

Note: not all of the bolts were installed or tightened for this photograph.

700-R4 (4L60-E) TRANSMISSION CROSSMEMBER

The 700-R4 transmission is very wide at the rear, and requires removing both of the stock mounting brackets in the transmission tunnel, in order to raise the transmission high enough to maintain stock driveline angles.

The transmission cross member shown is a prototype. There is plenty of room below the flat cross member to run the exhaust system.

TURBO-350 EXTENSION PLATE
If you are using a Turbo 350 transmission, the rear mount position is located about 2" forward of the 700-R4 (or Camaro T5) mount location. An extension plate, made from 1/4" thick steel, bolts to the Turbo 350 transmission mounting pad, and so the transmission mount can be located 2" rearward, so it can be mounted with the JTR/Stealth transmission cross member.

T56 TRANSMISSION CROSSMEMBER

If you want to install a T56 transmission, a special cross member is required, which is shaped to accept the T56 transmission.

The T56 transmission has a different mounting position than a T5 or 700-R4. This is a prototype transmission mount. The mount is positioned 1-1/8" lower, and 2-1/4" further back than a T5 or 700-R4 transmission.

The transmission cross member is mounted below the transmission ears due to the different mounting requirements.