Piston Slap: The Marquisification of a 1946 Ford?


Robert writes:

I have a 1946 Ford Sedan that I would like to update with a small block Ford 302, overdrive automatic transmission, and a higher speed rear end. I have a 1990 Grand Marquis for a donor car. The thing that’s stopping me is that I don’t know how to handle the electronic ignition and electronic fuel injection. Also, would you recommend installing the Mercury front suspension and steering or convert to the Mustang II option? The Grand Marquis has a frame with a bolt-on body. Could this be put under the ’46 Ford?

My goal is to have a good-looking old car with a reliable drivetrain as a mild cruiser that gets good gas mileage and has all the comforts of AC, power steering, and cruise control. I’m not interested in a high-performance hot rod. Any plans, thoughts, or advice would be appreciated.

Sajeev answers:

What a fantastic project! Before I go any further, let me insist that the information below is just a high level overview; it will gloss over serious engineering considerations that need to be considered due to Piston Slap’s nature as an easy-to-digest blog post. So with that caveat in mind …

The frame: Surprisingly, the Grand Marquis and the 1946 Ford have a very similar wheelbase; the Internet says they are only 3/10 inches different! With that in mind, its entirely possible that you could swap frames, but that’s only after measuring the 1946 Ford’s width at key points (cowl, radiator support, front and rear track, etc.) to ensure the wheels won’t be sticking out 2 inches extra at each corner, or something similarly awful elsewhere. I expect it will be and believe that a frame swap is more trouble than its worth.

Much, much better. Speedway Motors

The suspension: To be honest, the Grand Marquis’ suspension isn’t that great. Considering how much fabrication is required, I’d rather start with a 2003+ Panther Chassis Ford for a couple grand and get a far, far, faaaar superior suspension. But this is all too much work for the “mild cruiser” you desire, so make your life easier and get the aftermarket Mustang II-style suspension, as it comes with a perfectly engineered crossmember for your Ford sedan. (And please avoid aftermarket Mustang II control arms with Delrin or urethane bushings if you want a smooth ride.)

This isn’t an optional purchase. eBay | wipmyride

Fuel injection: With the chassis sorted, it’s time to get Ford’s EEC-IV wiring in order so you can get the Grand Marquis’ powertrain running. Many claim/believe this engine is the same as a 5.0 Mustang from the same era, except it has different heads, intake, cam, fuel injectors, firing order, and engine computer. I’m mentioning this because you might not want to buy an aftermarket 5.0 wiring harness, as it might not work with a Grand Marquis computer without modification. This is even more likely if your replacement harness is for a 5.0 Mustang running a mass-airflow sensor. So let’s avoid that whole mess and re-use the wiring in your donor car.

Here’s the thing: the EEC-IV fuel injection (and relevant ignition stuff) is mostly a standalone affair. Almost everything begins and ends at the computer (which is near the steering column). Aside from some wiring going to the fuel pump (and its shut off switch), a fuse box, an ignition switch, and the cruise control (which I expect you will delete), it’s a very straightforward affair. Well, in theory. In reality, you must purchase a Ford EVTM (electrical-vacuum-troubleshooting-manual) and use the “electronic engine control” section to separate EEC-IV wiring from the chassis of your donor Grand Marquis.

Moving that wiring over to a new home won’t be a walk in the park, but considering the width and length of the Grand Marquis, I am gonna remain hopeful that most wiring will be too long or your application, and not the other way around. And if I can buy Ford EVTM manuals and remove/install wiring for Project Valentino, so can you!

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