Race Car Modifications for the
Datsun 240Z including information
for a Ford V-8 Conversion

Written by Terry Oxandale

Power Plant

Ford engine in Datsun Chassis

The small-block Ford engine is a lightweight, high-powered alternative to the Datsun 6 cylinder. I have had considerable experience with the Ford engine over the years which helped lead me to this choice for an alternative to the stock Z engine. There is nothing wrong with the Z engine in that it can be made to be a high output motor, but after looking at the facts, I chose the alternative. This being because I felt 240hp was the maximum reliable horsepower I could count on, but unfortunately, I could not afford to build the Z motor to these figures due to the great expense involved in doing so. The Ford alternative offered a reliable 300+ horsepower, at a moderate price tag with a lighter weight engine and cheaper repairs should I have an engine failure. The Ford 289/302 weighs approximately 40 pounds less than the comparably set up Datsun 6 cylinder engine, and the Ford engine's center of gravity is further rearward too (with both engines located rearward as far as the firewall). So, with my reasoning for the swap explained, lets describe the process.

Engine support
Front engine plate

To support the engine I used aluminum plate bolted across both the front and rear ends of the block. On the front, this engine plate was sandwiched between the block and the timing chain cover. Naturally the area of the plate under the cover had to be removed where the timing gears and chain sat. Then with holes drilled in the plate wherever water pump/timing chain cover bolts screw into the block and water passages for the water pump, the cover was bolted to the engine block, sandwiching the front plate to the block. An extra cover gasket is needed to do this. Attaching a plate to the front of a Ford engine this way will cause minor problems elsewhere, as will now be discussed.

With the timing chain cover extended out away from the block by, the crankshaft snout now sticks out of the cover less than it would under normal or factory conditions. This in itself is no problem, but the harmonic balancer bolts onto the end of the crankshaft snout with the back of the balancer going into the front main seal (which now will be further forward than normal). To put the balancer/ cover geometry correct, I fabricated a thick ring, similar to a washer, with a key slot cut into it for the crankshaft key, and placed it onto the crankshaft snout and slid it all the way back to the shoulder that the balancer would normally butt up against (be sure that any radiused corners are taken into account here where this fabricated spacer contacts the crank shoulder). Then I bolted the balancer onto the snout until it butted against the new spacer (ring), thus sandwiching the spacer between the balancer and the crankshaft shoulder. Now everything is spaced correctly and everything tightens down to specified torque figures. The water pump and crankshaft pulleys will now also line up too, because both have now been moved forward by. It should be noted that with the engine just ahead of the firewall (with about 1" clearance), you should be able to set the front engine plate onto the very front edge of the stock Z 6 cylinder engine pedestals. Again, short pieces of angle aluminum where used to then bolt the engine plate onto these pedestals.

The 4 threaded holes on the bottom of the front cover (2 on each side) that are use to attach the oil pan, will not be aligned with the corresponding oil pan holes any more, due to the shift of the cover. These bolts are not absolutely necessary to hold the pan on in front due to the rigidity of the pan, but oil will leak out these holes if not sealed well. I used a piece of .001" steel shim, slid between the pan gasket and the cover, with sealant applied to both sides.

Many callers interested in this swap who choose only to use this conversion for "spirited street driving" could very well do without the rear plate entirely, thus eliminating the header interference. But this option will be dictated by power output, tire size, suspension, and driving style.

Rear engine plate
The rear engine plate was quite a bit simpler. This plate was sandwiched between the engine and the bell housing. And again, the area inside the bell housing had to be removed to make room for the flywheel. With the bolt holes drilled to match the six holes in the bell housing to match the block, I attached the bell housing to the engine, sandwiching the rear engine plate in position. With the bell housing moved rearward by the thickness of the plate (1/4") I found I needed to compensate the less penetration of the transmission input shaft into the pilot bearing in the crankshaft. This was done by using a factory Ford part (# C5TZ-7600D, I think) that is a special pilot bearing used to put the short-shafted big block transmissions behind a small block engine (this was done on the 351 Cleveland motors). This special pilot bearing is about 3/8" thicker than the normal bearing, thus making up for the lost due to the rear engine plate spacing. Now both plates are attached to the engine, and now we mount the plates/engine assembly into the Z chassis. Keep in mind here that the starter motor must bolt onto the aluminum plate, and not the bellhousing in order to maintain correct gear mesh. So make sure that the rear plate you make also includes an area matching the bellhousing in the area of the starter. Remember, the starter motor mounting surface is on the same plane as the rear of the block, which may not necessarily be the bellhousing.

For use with the original front cross member, I chose to fabricate a bracket to replace the stock rubber Z engine mounts by using a short piece of angle aluminum to connect the horizontal surface of the Z engine mount pedestal to the vertical surface of the new engine plates. This is an over simplification of the final design, but in essence, it was only a 90 degree bent piece of metal to connect the two surfaces rigidly. For an attachment point for the rear plate, I first welded a saddle of 1/8" angle steel over the frame rail in the rear of the engine bay. Then I welded a vertical plate of 1/8" thick steel onto this saddle, perpendicular to the saddle and parallel to the firewall and engine plate. The rear engine plate now bolts against this piece in back on both frame rails, giving four hard points at which the engine is attached to the Z chassis, thus reinforcing the front end rigidity by using the block to become a part of the chassis. With little trial and error I was able to position the rear plate about 1" ahead of the firewall (to allow easy separation of transmission from the engine). This, with correct vertical spacing, allowed the T-5 transmission to fit easily into the Z transmission tunnel, with the shifter handle positioned just 1" forward of the stock Z transmission handle, and the oil pan of the Ford engine will hang down about 1" lower than the location of the original Z pan. A higher and more forward position of the engine would be no problem, but I chose to go to the limits of the spacing envelope to maximize the weight distribution benefits of this engine.

Note: I later chose to make a whole new crossmember, after I decided to replace the original Z steering rack with a Ford power assist rack off of the '79-'83 Mustangs and T-Birds, and also after I decided to move the cross member (and the front axle centerline to increase the caster) forward 1-1/4". For further explanation, see "Caster Changes".

Ancillary functions
With the block attached to the chassis in the way described above, I found other problems cropping up. One of them was the lack of clearance for the oil filter. At the block's present location, the steering rod interferes with the placement of the standard sized Datsun/Ford oil filter (they are one and the same). I was able to use a Fram PH3651A (which is used on some Datsun motors) because it was just a shortened version of the regular filter. It was only 3-1/2" long, making it just barely usable. Also, the left side Z 6 cylinder engine pedestal may cause a slight amount of interference with this filter too, but this small amount of interference can be eliminated by grinding about 3/4" off the back side for filter clearance. But, I will be racing this car, so I decided to use a remote filter assembly, thus eliminating this oil filter problem entirely.

Another problem I had was with the exhaust manifolds. My original plans called for the use of the "shorty" exhaust headers, sold by various vendors to be an exact size replacement to the factory headers, to keep weight and size to a minimum. But the rear engine plates interfered with these (just barely). A different shaped design on the rear engine plate (such as a plate bolted onto the outside of the bell housing, instead of between the engine and transmission, would move the plate rearward just far enough to allow use of the "shorty" headers) could probably allow me to use these headers, but I am using Motorsports J302 aluminum heads, with the big exhaust ports and wider bolt pattern to allow for big tubes without being crimped for bolt clearance at the port. So rather than redo the rear engine plate (I could probably even eliminate this plate entirely, and have the engine supported only by the front plate, and the transmission mount only). I decided to make my own headers out of 1-3/4" mandrel bent tubing kits sold by Hooker Headers. These ended up being heavier than the shorties, but I'm sure they will perform better with their equal length, and longer tubes.

The front carburetor (a 2 X 4 setup) air filter flange is about 4" below the hood, at the present block location. This should be ample room for a good air filter. On a single carburetor setup, and a lower profile manifold, you will likely have 5 clearance to the hood.


Power Plant Radiator & Support T-5 Transmission Information
Ford Drive Shaft Half Shaft Modifications Differential Change
Z-to-ZX Brake Update Brake Master Cylinder Caster Changes
Steering Rack Strut Modifications Custom Sway Bars
Aluminum Differential Upright Weights Costs

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This page last updated 23 September 1997.
Problems? Suggestions? email Michael S. White at mswhite@sos.net