Below is a copy of a write-up I did many years ago adapting a B20 to my PV444. Not sure how much will work for a B16 544 but I imagine a lot will. So here it is for what it is worth….

Adapting a PV444 to B18/B20

I started with a PV444 that had not run for years. The engine had very low compression. My goal is to drive the car a lot, keeping the appearance of the PV444 but having it be as reliable and easy to maintain as I reasonably can. I had no interest in “showing” the car. I converted it to the B18/B20 for two reasons: 1. Better performance from the increased power and 4.11 v/s 4.56 rear axle; 2. Better availability of parts with the later engine, drive train, brakes and electrical equipment.

Also I had local availability of a rusty 1964 544 donor car with a blown engine and a 65,000 mile B20 engine from an even rustier 1974 142. Here is what I have found so far to be involved in the change.

Cooling

Used the front center section from the B18 544. This uses the B18 radiator with hose fittings located properly for the B20. It also provides improved hood support and operation with spring counter weight mechanism.

The B16 radiator is narrower and deeper than that of the B18 and the center mounting point for the housing is about 1 inch lower on the B16 frame. I shimmed the space with pieces of pipe around the two vertical bolts. With the shims the housing bolts, which were permanently attached to the B18 shell on my car, were not long enough. So I drilled holes for two additional bolts in the same area, supporting them with pieces of pipe, as well

Used the B18 thermostat housing to match diameter of B18 radiator hose fittings. The one on my B20 had a larger diameter outlet. I also needed different fitting for the heater hose to block connection.

Electrical – change to 12-volt system

Replaced all light bulbs and headlamps with 12-volt units from the 544. This includes five lights in the instrument cluster, the interior light and the license plate lights. I also used the 544 headlight switch instead of the cable operated one from the 444. With 544 switch one can dim the instrument lights with a twist of the switch knob.

Used the alternator and voltage regulator from the B20.

Used the windshield wiper motor from the 544. The 544 wiper motor bolted into the 444 linkage without alteration but had a larger diameter shaft, which required enlarging the hole in the 444 linkage. The wiring to the 444 wiper switch is the same.

Used the heater motor from the 544. The heater controls on my 444 were badly deteriorated I used the heater controls from the 544 rather than find new 444 ones. This required reworking the opening around these controls. I mounted the air and temperature controls where the 444 controls had been. Centered below these I mounted the push-pull fan switch from the 544. It has connections matching those for the two speed 544 heater motor. (Use the 444 controls if you have or can find a decent set. I now regret this choice.)

Replaced the 6-volt turn signal blinker from the 444 with the 12-volt unit from the 544.

Replaced the deteriorated 6-volt fuel sender with a generic 12-volt Stewart Warner unit.

Replaced the armored ignition switch/coil and distributor ignition points with a Petronix breakerless distributor plate, Petronix coil and an off the shelf ignition switch. (The key was broken off in the ignition of my donor car and I could not figure out how to get the armored unit from the donor car. But I am happy with this change. I like the Petronix arrangement better.)

Replaced fuses with lower amp rated ones appropriate to the 12-volt system.

Where I used 544 switches I replaced the black plastic knobs with chrome knobs from the cabinet shop (drawer pulls) at the local hardware store. I drilled and tapped these with threads to match the 6mm threads on the switches.

Mechanical

Used the clutch housing, transmission, drive shaft, rear axle and brakes from the 544.

Retained the dashboard-mounted handbrake from the 444 and adapted its linkage to the handbrake cables from the 544.

Removed the clutch linkage pivot point from the 544 and attached it to the 444, enabling use of 544 clutch linkage parts.

Used the front motor mount brackets from the B16 instead of those from the B18 or B20. The rear transmission mount was unchanged except that I replaced the rubber insert.

Replaced the 444 master cylinder with the master cylinder and remote reservoir from the 544. The 544 master cylinder provides more clearance for the B18/B20 starter location on the left side of the engine.

Fitted a longer hose between the oil pressure gauge fitting location on the B20 block to the 444 oil pressure fitting on the firewall.

Replaced the fuel injection with the B18 S.U. carbs and manifold. Filled the injector holes with freeze plugs. Used the 444 choke cable because I preferred its chrome knob which is like the other 444 controls.

Replaced B16 throttle linkage with B18 linkage from the 544. This required: cutting the bracket from the 544 firewall and installing it on the 444 firewall (with a hole for the linkage to pass through) and relocating the pivot points from the center section behind the firewall of the 544 to that of the 444. I could not quite get the linkage to thread through the 444 center section (it is slightly different than the B18 544) and so cut it and rejoined it with a mechanical “union”.

Used the dual down pipe exhaust pipe from the B20. I plan to have a local shop fabricate the rest of the system and hang it from the original mount locations using just the rear turbo muffler from a 240 as in the IPD system for 240..

You can use the original radiator, but to do so you'll want to find an early B18 thermostat housing - this one will fit the B16 radiator hose easily. Connecting the lower hose is more of an issue - you'll need a long piece of coolant hose and/or a number of 90 degree elbows to connect everything up. It can work but it's not at all graceful.

A radiator shop can move that lower hose fitting from the driver side of the radiator over to the passenger side, and then all will be well. The radiator itself, unless it's compromised, can keep a B20 cool. Unless you're in Texas or something, then I don't know what happens.

The engine mount brackets from the B16 bolt onto the B20, and that's the ONLY factory engine mount bracket that will allow you to simply install the engine. B18 544 brackets don't work, 122 brackets don't work, 1800, 140, 164 brackets don't work.

The bracket for the clutch linkage that's welded to the frame member is in the wrong place for the B18/20 setup. You can cut it off and reweld it; or you can use a heim joint bolted through the flange on the frame member. Heim joints are pretty nice, as they don't scrape and grind like the original stuff.

Once the B18 is in place, you'll notice that the starter is directly above the brake master cylinder, and that you can no longer check the fluid level without first removing the starter. You can either live with it like that, or you can switch to a later master cylinder with remote reservoir; or you can get an adaptor cap for your current master cylinder which will then allow you to add the remote reservoir and associated plumbing (this is the route I'd go).

If your current transmission is a 3 speed, the driveline won't be the right length for the new M40. If it's a 4 speed, the length will be ok and you'll need only worry about whether or not the flange is the right size.

Cheers -

Cameron
Rose City

I did this same conversion 20 yrs ago, I had the radiator recored with a modern core, it never over heated. I also used a hydraulic clutch using a 122 bell housing, and the motor mounts are tricky, can't remember what I did with that issue

The radiator may be more of a problem.
I think a B18 linkage assembly will be fine for the clutch - but not positive.
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig