V8 Swap into a Mklll

By Karl Schluter -Low Zep

****Do check laws in your country before doing any of this work and read the Safety link on this site. ****

This swap has measurements taken from my 1964 Zephyr 6 (New Zealand assembled, right hand drive). View my car under My Mklll V8 to see other pictures of underbonnet details and the accompanying write-ups for other details.

A V8 swap into a Zephyr is a natural whether Chev, Ford or Rover etc. Do consider a later motor that is lead free. The Ford Windsor model is very similar in weight to the Zephyr straight 6, more so if the V8 is fitted with an alloy intake, headers and alloy water pump. The swap featured here has the motor sitting nice and low as well. The centre line of the crankshaft and transmission should be parallel at all times to the centre line of the car when looking down from above. This helps maintain long driveshaft universal life.

With the dimensions in this swap, the battery can remain in its factory position and the hand brake can be slightly modified to still work in the factory design if original cast iron exhaust manifolds are used. However, I do recommend going to a floor mounted lever hand brake or a Japanese or similar modified handbrake that pulls out from the dash in the factory position. Cars factory fitted with automatics have more room in the transmission tunnel, although this swap does not require any cutting etc to the floor pan or firewall if using the C4 automatic or 4 speed top loader transmission, except for a small incision for the gear stick. The factory column shift in factory fitted automatic cars can be modified to shift the C4 transmission.

The factory 5/16ths-fuel line will work for most engines unless running a large 4-barrel or fuel injection.

The crossmember measurements are in millimetres and are not to be taken literally, as they will be different from car to car. I strongly recommend removing the engine crossmember for this work to check it thoroughly for cracks and to make for a better welding job.

When adapting the wiring for a V8, the factory solenoid (with remote starter) can be reused if the early V8"rat trap" starter motor is used. Use the factory Zephyr/Zodiac 6 sender units for the oil pressure and water temperature, installing these on the V8 motor. Now is also a good time to update to an  Alternator .

For a 289 or 302w motor the standard Mklll radiator can be reused provided it is in good condition and you use a low temperature opening thermostat. I do recommend a good flex fan and a shroud, even if just for safety reasons although a properly designed one can help cooling. If your car has been recored with a cheaper 2 row radiator in the past, you will need to change to a 3 row (closer to the standard radiator). If in doubt, check out a radiator shop. At the very least, I recommend getting the radiator rodded by a good shop and pressure tested. The factory inlet and outlet can be left as is on the standard radiator if the right water pump is used, as both left hand and right hand outlet water pumps are available. The top hose can be made of 2 x 90dg right angles of radiator hose and a length of stainless tube. I also like to install a radiator reservoir system to add water volume and hose life.

The Mklll factory driveshaft can be reused with a larger V8 car universal installed with matching yoke at the transmission end and a Mklll Zodiac universal at the rear end with matching Mklll diff flange. I run the driveshaft all the way into the rear of the transmission then back it out one inch and have that as the driveshafts overall measurement. The inch free movement is to allow the driveshaft to move in and out of the back of the transmission as the differential moves under suspension travel. If in doubt about driveshaft measurements, I recommend talking to the shop that is doing the work for their advice first, plus also getting the driveshaft balanced. Now is also a good time to make up a driveshaft safety loop, placed 6 inches back from the front universal and mounted to the floor pan. I have successfully run the standard Mklll diff however, both Borg-warner diffs from Ford Falcons or Chrysler Valiants etc can be modified to fit as well as Ford 8 and 9-inch diffs and even Volvo!

With the crossmember in these plans, mounting the motor as detailed, extractors can be made to fit, however, the steering box side (right hand drive) is very tight and is made easier if the factory handbrake system has been installed elsewhere as detailed above (at the start of this article). The top picture shows the drivers side (right hand drive) header system which is quite tight, but does fit very well with careful work and trial fitting. The left hand side is standard "off the shelf" 1970 Ford Falcon (or there abouts), so you could pick up a set and modify them to fit a Zephyr. The system in the photos have 1.5 inch primaries and 3 inch collectors. Its not until the rest of the motor is modified that you'll feel much effect with fitting headers to the motor over the standard cast iron manifolds. A 5.0 litre V8 can be run quite successfully with a single exhaust system, however, there is room for a good performance twin system, mounting oval V8 style mufflers under the rear seat floor pan area.

Engine Cross member

Below is the right hand side:

Both these pictures are taken from looking on top of the car looking down into the engine bay on their relevant sides. Again, the factory crossmember upright is used with just a built on section extending out towards the block with a 90mm section of tube.

The mounts to use are from the 1970’s Ford range and are very common. They are a through bolt mounting design, meaning they have 2 outside flanges that mate to the modified crossmembers 90mm tube with a through bolt. These mounts are easy to come by and are easy to line up during engine work.

The swap outlined here is for a front sump Windsor so if you are changing from a different type of sump, you will require the matching oil pickup. American Windsors with early Mustang / Fairlane are usually fitted with this sump. Most Windsors are fitted with this style of sump regardless, unless fitted to a Bronco or later model 5.0 litre fuel injected car.

This is a side view of the gear box crossmember, it needs an 80mm wide plate, 180mm’s long (crossways) 8mm thick, welded to the front of the standard Mklll crossmember. 2 transmission mount holes will need drilled in this plate once the motor and gearbox are centred in the car. I have left the exact measurement out as it can change from car to car, transmission to transmission. Not often done in this swap but something I strongly recommend,is 2 triangle gussets be added at each end of the plate. To further add strength to the crossmember, modify the crossmember end mounts as seen in Gear box cross member mount fix .

Along with this swap, I recommend at the least the steering box be braced as detailed in Steering box fix .

A strut tower brace also adds strength to the strut towers and is an easy and worth while strengthening aid  Strengthening strut towers .

Disclaimer: The advice and guidelines given are given in good faith and the owners and managers of this site can take no responsibility for injuries sustained while carrying out the described tasks and procedures or any consequences arising.