Cast iron meets chemistry: Salvaging a rusty engine block

Courtesy of Rodney Bauman

Despite what its moniker implies, Henry Ford’s “Tin Lizzie” wasn’t entirely made of tin. Rather than listing the ingredients, let’s just talk about engine block castings for now.

Among current-era Model T engine rebuilders, the 1926-’27 blocks are pretty much preferred, but those two-year-only castings are becoming rather scarce. The one we’ll be working with here was supplied by Dieter Lange, the southern California Model T engine guru.

With a counterweighted Model A crankshaft and some other internal modifications, this Lange-built engine was built to run with the big dogs of timed rally competition.

So, we’ve just seen the rusty dribble. With our engine idling at the parts store curb, this popular leak-stopping product will surely plug the pinhole. Courtesy of Rodney Bauman

The engine’s initial shakedown took place in the deep south of southern California. That was for the Model T Ford Club of San Diego’s 31st Annual Speedster Run. Since the car was a fresh build, we’d expected that it might have some minor bugs. Sure enough, it did, but the engine performed flawlessly.

At some point during the event, while parked out-front the headquarters motel, a small puddle of coolant appeared as a rusty pinhole made its presence known. At times like these, it’s good to have chemistry on our side.

From the nearest open parts store, a popular leak-stopping product that you’ll quite likely recognize was introduced through the radiator. From there, as the car was driven, the problem simply went away.

When a certain job demands it, I’m not opposed to cheating. I’ve used the aforementioned product to stop leaks in radiators, heater cores and so on. I’ve even stood and watched as it filled in for a failing freeze plug. As that engine idled, the coolant stream slowed to a trickle, then stopped, and that was that for years.

The leak was stopped for roughly three years, ’til the first time the speedster sat all winter long. It’s pretty obvious the leak-stopping product is still present. Courtesy of Rodney Bauman

In the case of our Model T speedster, however, it’s not exactly driven daily. From my own previous experience, regular driving is the key to such quick-fix chemical success.

The speedster is now in Montana. During its first year here, it was stored all winter long. By spring, it sprung the same old leak in the same rusty section of water jacket.

It’s the same old place, for sure. Again, from previous experience, I’m confident the leak would not have recurred if the engine ran more regularly. Courtesy of Rodney Bauman

For the repair job at hand, we’ll still rely upon chemistry. This time, however, we’ll take an additional step. We’ll drain, strain and retain our chemical-fortified coolant. Then we’ll employ another popular parts store product — a two-part epoxy that you’ll also likely recognize.

Will this be just a bandage? Well, we’re in a pinch. A rust-free 1926-’27 Model T engine block would be pretty tough to come by, and anyway, we’re not about to start again from scratch. Together, our two chemical companions should form a closer-to-permanent leak-stopping team. At this stage in the game, we’ve got little to lose by trying.

Now before we begin the step-by-step technical portion of our story, we’d like to skip farther ahead and expound the good news. This worked! At the time of this typewriting, the little speedster has been driven enough that we’ve relaxed a bit, or two. We’re no longer just watching it leak — at least not
in the same old place.

With coolant drained, we’ll dry the porous casting. Just beyond the thermometer is an external block heater. At this temperature, it’s safe for overnight. Courtesy of Rodney Bauman

The very next morning we’ll apply protective masking. Then we’ll grind the affected area clean with a semi-spent 3-inch Roloc-type abrasive disc. Courtesy of Rodney Bauman

For deeper cleaning, a spritz of starting fluid helps. We’ll try to wipe this dry with clean disposable toweling before it can completely evaporate on its own. Courtesy of Rodney Bauman

So, here’s our two-part epoxy product of choice. Equal parts are mixed on a clean surface. Back at the pinhole, masking is freshened up as necessary, as we go. Courtesy of Rodney Bauman

Next, the mixed product is smeared firmly into the pores of the casting. Time to cure depends upon temperature. Let’s play it safe — and allow ample time Courtesy of Rodney Bauman

Since our smear was pretty smooth, this step is almost optional. With used sections of 120-grit sandpaper, we’ll level the high spots and go for feathered edges. Courtesy of Rodney Bauman

With time between, we’ll apply two coats of high-temp black for a match. From here, let’s consider this good engine’s rusty block to be salvaged Courtesy of Rodney Bauman

Looking for more resto tips? Here are a few more articles for your reading enjoyment.

https://www.oldcarsweekly.com/features/old-cars-restoration-in-with-the-good-air

https://www.oldcarsweekly.com/features/old-cars-restoration-bedding-your-brakes-rehab

https://www.oldcarsweekly.com/features/old-cars-restoration-basics-replacing-weatherstrip-rehab

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Model T engine block pinhole leak fix restoration tips

Rotten Rodney BaumanAuthor