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Gow To: Evaluating a Model B four-banger

Published in blog.hemmings.com

The Revelator needs a new engine. This is how it’s being done economically. Photo by Dan Beaudry, others by David Conwill and as credited

how-to (hou-tü) adj. giving practical instruction and advice (as on a craft)

gow (gou) n. automobile modified for speed and performance in the pre-WWII style

gow-to (gou-tü) adj. giving practical instruction and advice for modifying automobiles for speed and performance in the pre-WWII style

The Internet is a blade that cuts both ways for the old-car enthusiast. Information that was hard to come by for many years has become readily accessible. But the holders of that information often believe that the way they espouse is the ONLY way.

The truth is, though, that there is often more than one way to do a thing, and it’s often more efficient and economical to just do a thing well instead of waiting until it can be done in the ideal manner. Modern business types refer to this as not letting the perfect be the enemy of the good.

Old engines are a great case study for this. Recently, former Hemmings managing editor Dan Beaudry decided that the best way to get rid of some of the issues plaguing his 1929 Ford Model A Tudor, The Revelator, would be to execute his planned engine and transmission swap—installing a 1932-’34 Ford Model B four-cylinder and a 1939 Ford three-speed in place of the original four and its associated crash box.

The first phase in that process was to evaluate the Model B engine Dan had purchased. As interest in hopping up vintage engines like flathead Ford V-8s and their elder siblings the Model T, A, and B four-cylinders has revived over the past 25 years or so (yeah, it kicked off in the ‘90s), a lot of opinions, facts, and anecdotal evidence have been bandied about through message boards and social media.

One could easily get the impression that to use any prewar engine in a restoration or hop up requires it to be pulled down to a bare block, hot tanked, magnafluxed, re-machined and built from scratch—preferably with insert bearings, modified oiling systems, and other tricks to make it a high-rpm powerhouse equivalent to a modern engine. There is certainly nothing wrong to that approach, but it takes cubic dollars, and it’s a huge psychological barrier to a lot of younger and/or less-affluent customers.

There’s another way, though, and one that’s equivalent to what was often done back when these cars were a whole lot newer and younger and/or less-affluent folks were hopping them up for the first time. Brian Cholerton, of Islip Terrace, New York, and his son, Matthew, have built a handsome pair of speedsters using this approach. Both have solid, reliable powerplants. They’re not world beaters, but they often come out ahead of more exotic equipment that proves fragile when actually driven aggressively.

Brian is an advocate of not letting the perfect be the enemy of the good, so over the weekend of June 22-23, when the Barnstormers Vintage Speed Club met up at Brian’s house for the Port Washington Hill Climb, he invited Dan to bring down his Model B engine for an inspection, the results of which would tell a lot about how much investment was actually needed to make a fun, reliable powerplant for The Revelator. Follow along and see what we found out.

This is the engine in Brian Cholerton’s 1929 Ford speedster. The philosophy set out here was used in evaluating this engine and it has served him for a long time without issue, though it is now slated to be replaced by a built Model B engine that just came back from the shop.

This is Dan’s engine, cleaned up and painted white, but otherwise untouched. Matt Cholerton removed the head so the deck and bores could be inspected. Laying the engine on a cart made it far easier to work with than having it on a stand, though it is a good idea to have three fairly strong folks present to move it around when necessary.

One disadvantage to the Model B engine versus the Model A is that B’s are known for thin decks and the resultant cracking. The pistons, cylinders, and valves look OK, but the deck required closer inspection.

The Cholertons thought they spotted a crack between the number-two cylinder and its exhaust valve. That’s not surprising, given the heat involved.

To get a closer look, a brass wire brush was used to remove the carbon. The brass bristles won’t mar the steel deck of the block.

Sure enough, there was a crack, as indicated by the red arrows. The good news is that it’s not fatal and isn’t even bad enough to warrant pinning right now. The engine can be run as is, and when the time comes for a rebuild, it can be pinned and welded. If it propagates all the way to the cylinder, sleeving will take care of it.

This is the fresh Model B engine going into Brian’s speedster. It has similar cracking repaired on it and the bores have been sleeved back to standard.

When running a Model B engine in a Model A, owners often choose to run a Model A style cylinder head. Those heads lack the steam holes, shown here on Dan’s stock Model B head. Dan plans to run a Model A Police head, so he won’t have these and thus something needed to be done to the block to compensate.

Compare the Model B head (top) with the Model A head. Note the lack of steam holes in the Model A head.

Brian shows the gasket off his Model B. Initially, he had run an A head against the B block without plugging the steam holes. Eventually the gasket blew out around the steam holes–sapping power and allowing coolant into the cylinders. He rectified the situation before it caused any damage, but hydrolocking could have resulted if the problem had been ignored.

Dan ran a tap into the steam holes in his block. They are approximately 8 mm and can easily be threaded to that size.

Brian shows off the grub screws (aka Allen-head set screws) that were threaded into the block to seal off the steam holes.

Dan coated the grub screws with JB Weld so they would stay where they were put.

The grub screws were run into the now-threaded steam holes to a level just below the deck. It’s better they be deeper than sticking out.

With the grub screws installed (only one is shown here), the whole thing was covered with JB Weld and later sanded smooth.

Brian’s engine shows the finished result once the hardened JB Weld has been sanded down, a process Brian compares with puttying over nail holes in drywall.

With the deck inspected, attentions were turned to the bottom end of the engine. The three poured-babbitt main bearings were the main area of concern. The bolts holding in the main caps run through the crankcase, meaning two sockets were required to remove them. Dan and Matt started with the front main.

Pulling the front main resulted in a minor celebration. It still had shims in place (factory engines came with a stack of shims that could be removed over time to compensate for wear–the presence of shims in a used engine is hopefully an indicator it hasn’t experienced much wear over its service life) and the babbitt wasn’t deformed from the crankshaft pounding it. Note the smooth, fully intact babbitt metal and oiling groove. The oiling groove is where bearing deformation is usually spotted.

The main bearing caps each had stacks of three shims remaining (two are stuck together here), approximately half of the factory stack. Typically, Brian and Matt will put an unknown engine back together without any shims, tighten down the center main, and see if the crank will spin. A crank that spins without any shims is an indicator that the bottom end probably needs refreshing. With so many shims remaining in Dan’s engine, it was decided to just reinstall the shims and assume things were good. If there is any knock, Dan will remove a shim from each main bearing until the knock goes away.

To get at the center main, it was necessary to remove the cover on the valve gallery, as the end of one of the bolts is only accessible from inside.

Although it was pretty thoroughly sludged up, the gallery otherwise looked good. The spring near the gallery opening surrounds the distributor/oil-pump drive. All that had to come out for access to the bolt holding the center main.

The lump of sludge with the cotter pin sticking out of it is the hardware holding the center main in on this side. The hole in front is where the oil-pump drive was located.

The rear main was as clean and nice as the front. It also had the same number of shims.

With all of the main caps removed and inspected, Matt pulled the crankshaft down slightly (it was still attached to the pistons and rods) to inspect the upper part of the main bearings.

When the crankshaft didn’t want to move, Matt enlisted clubmate Kevin Carlson to tap a mallet handle against the pistons, persuading them to slide down in the cylinder.

With the crankshaft pulled down a bit, Matt was able to use a light to inspect the bearings. They were just as nice as their mates on the bottom.

While Ford used castellated nuts and cotter pins to retain the mains and rod bearings, Brian and Matt use these self-lockng ARP 12-point fasteners (p/n 300-8334 for the mains, p/n 300-8333 for the rods). The advantages, Brian tells us, are that you can torque them down without worrying about whether the castellations line up with the hole drilled in the bolt and, more importantly in Dan’s case, eliminating the cotter pins allows the larger Model B bearings to clear a Model A oil pan.

Oiling is critical on all engines, so it was only natural that Matt cleaned up and looked over the oil-pump drive while it was out. It looked good, but had the drive gear (at right) been chewed up, it is replaceable by removing the roll pin (at left) and disassembling the drive.

One of the advantages to a Model B engine is the improved oiling versus the splash system on the Model A. Kevin pointed out some of the additional oiling holes on the block and expounded on the necessity of making sure they are clear of gunk and debris so the main bearings get a constant supply of oil.

To check flow and generally de-gunk the oil passages, Kevin sprayed brake cleaner down the holes. Make sure you use the straw attachment for this part–Dan’s block lost a bit of paint from some stray brake cleaner.

One of the mods Brian recommends to improve oiling when using a Model A oil pump, which Dan is holding here, is to turn down the shaft, allowing a greater volume of oil to flow past. Brian is holding a modified shaft.

After removing the base of the oil-pump (the round plate in the tray with four holes), Dan was able to slide the unmodified shaft out of his Model A oil pump.

Brian’s modified Model A oil-pump shaft measures 0.408 inch. It was turned down between the bearing areas.

A nicely chamfered edge prevents stress on the turned-down oil-pump shaft.

The set screw that holds in the oil pump is where Brian puts his oil-pressure sensor. Because the effects of the additional volume will only become greater pressure beyond where the feed emerges into the oiling passeges, the gauge won’t reflect any more pressure with the modified shaft, but it does give values with which to compare as the car is run.

The modified and un-modified oil-pump shafts. Note that the oil stains on the unmodified shafts indicate perfectly where the shaft should be turned down.

Because everything else on the engine looked so good, it was decided to leave the rod bearings alone. New, re-babbitted (or inserted, if you prefer) connecting rods are available on an exchange basis, so if upon starting up the engine, Dan discovers rod knock, he can change the rods out at that time. With the engine in satisfactory condition, the next steps will involve a cylinder head and cam swap and an adapter to mount the V-8 transmission. Stay tuned!