Projects Model A Traditional Hotrod - my style: make it look stock but go fast

I built this little hotrod in 6 months last winter in the backyard and took it on a 1990 mile road trip last summer (but as you'll see it was only under it's own power for the first 80 miles and the last 620 miles due to unforeseen issues, ie. a hole in the block that was repaired in a hotel parking lot and is still running strong today) from Miami to Copper Harbor, Michigan on Hwy 41...the idea was to make it look stock to everyone except a Model A aficionado, but safely go 75+ MPH on modern highways. Except for the wheels, I think I achieved that goal. It has a lot of hand fabricated parts and unique ideas to build a traditional style hotrod that I thought I'd post here in case they can help someone else out with their project. After the trip, I made a story book on Shutterfly and I just copied and pasted the pictures and captions from that book here, so its written for a broader audience than just car guys. If you want more details on "exactly how I did x, y, and z" please let me know. I hope you like the story and I hope some of the things I did can help others who want to build a "1950's high school parking lot hotrod" that can accelerate, stop, and handle well enough to be driven in modern interstate traffic without fear of death every time brake lights come on from every car in front of you at 75 MPH.

This is my favorite picture of the "finished" car that was taken somewhere in northern Georgia.

 

I started with a decent Model A, but not too decent, I'm not a fan of chopping up a perfectly good car just to make a hotrod. This one is rust free - but has issues, the body work (all lower panels patched) is quite wavy, there's no interior, the 4-banger shook badly above 1000 RPM, and it was impossible to drive above 15 MPH due to a severe case of death wobble.

 

Chapter 1: The Brakes

The roads, cars, and traffic have changed substantially since the 1930's.

The Model A was perfect for what is was designed to do...30 MPH down dirt roads and across farm fields.

Ford could not have envisioned that someday, someone would want to drive his Model A at 75 MPH down a four lane highway with hundreds of other cars that can out maneuver and stop way faster than the old car could every hope to do.

So, in January 2024 the work began to improve upon the stock Model A and transform it into something that looks stock but can be driven at 75+ MPH down the interstate and be able to handle and stop well enough to be safe in modern traffic. Which means updating the engine, transmission, brakes, steering, rear axle, front and rear suspension, etc.

First things first: The brakes...

 

Drum Brakes and Mr. Ford


On the right is a stock Model A drum, on the left is one of the new drums to be fitted to the Model A.

Model A's, and, in fact all Fords from 1928 - 1938 had mechanical brakes, meaning, there were rods, levers, and in some years, wire cables going from the brake pedal to the brake shoes on each wheel. This was a big improvement over the Model T which only had a single brake in the transmission, unless you opted for the "Rocky Mountain" brakes in which case you could get a Model T with two brakes, one on each rear wheel, but still none on the front wheels!

Ford started using hydraulic brakes in 1939. They used shoes that pivoted on a dowel such that most of the stopping power was concentrated on the top half of the drum. By 1949 all US car manufactures switched to Bendix style or "self energizing" drum brakes in which all of the shoe pushes evenly on the drum, a design that is still used today on most car and truck drum brakes.

Although the post-war drum brake was a superior design...they simply do not stop like modern disk brakes.

But, when it comes to brakes, bigger means more stopping power, so we got the biggest drum brakes that would reasonably fit from the rear end of a 1996 Ford 1-ton van, which also have the same exact script oval Ford logo as the rest of the Model A parts and has "Bendix" stamped right below the Ford logo.

For size comparison, the Model A brakes measure 1-1/2" x 11", which equates to 142 sq-in of friction surface area, the new brakes measure 3-1/2" x 12", which is 396 sq in. Meaning the new brakes have 2.7 times more friction surface area, and therefore, with everything else being equal, they have 2.7 times more stopping power!

 

Fitting 1996 Ford Brakes to a Model A:


Model A baking plate.


Model A backing plate pie-cut and bent in preparation for mating to '96 Ford backing plate.


'96 Ford backing plate cut out to "match" pie-cut Model A.

 

Fitting the pie-cut pieces.


The two backing plates fitted together and ready for welding.


All welded up.

 

"Turning" the Drums:


Turning the outside of the new drums to reduce bulk and weight, took off about 10lbs each!


Cutting a radius into the drum using the jig pictured below to be an X-Y axis stop for the lathe's cross slide and apron.





Backing plate assembled to the the axle ready for paint.

 

Front Hubs:

Front hubs were modified for the drums and for any wheel from 1932 - 1948 Ford car or 1932 - 1996 Ford truck.


Stock Model A hub which is made from stamped steel.


First of two plates to be welded to the hub to make wheel and drum mounting bosses.


Turning a hub on the lathe.

 

Both hubs machined to accept new brake drums and wheels. Next is to drill holes and install the wheel studs.

 

Front Brakes Assembled:



Note the use of 3" long wheel studs, this was done because originally the plan was to widen and strengthen the stock wire wheels which requires ~ 1-1/2" think adapters. The 3" studs would then be cut to length. As it turns out, we ran out of time to modify the stock wheels, so the car has 1970's Ford truck wheels on it now, but maybe in the future I'll adapt the stock wheels.

Also, Model A's never came with grease caps, the wheel bearing was left exposed to the elements covered only by the hub caps. These grease caps are from Snyder's Antique auto parts and are a good upgrade.

 

Chapter Two - The Steering:

Model A steering boxes worked fine for what they were designed to do...turn 3-1/2" wide, stiff walled, bias ply tires on dirt. They don't work very well with modern wide radial tires on asphalt. Starting in the 1950's hotrodders would upgrade to a later steering box from the late 1930s or 1940s, with the most favorite swap from an F-1 Ford truck. These latter boxes have rollers between the gears that make turning significantly easier. However, the stock headlight switch is in the center of the steering wheel, so when swapping to a latter box, the stock switches go away.

In keeping with the goal of making the Model A look as stock as possible, I decided to keep the stock steering box, which allowed us to retain the stock steering wheel, headlight switches, etc.

To overcome the stock steering box's limitations, I completely re-engineered the front steering to accept 1963 - 1982 Corvette power steering cylinder and valve with an electric power steering pump mounted in the trunk.



Fabricating New Steering Arms:


Left to right: 1) round stock to start with, 2) round stock with mounting boss, shaft, and threads cut into it on the lathe, 3) arm tapered on the lathe, 4) stock Model A steering arm.


Left to right: 1) round stock to start with, 2 & 3) steering arms after being bent to shape, ends flattened and tapered tie rod mount holes machined, 4) stock Model A arm.


New steering arm mounted to spindle with tie rod end temporarily installed. The longer steering arms were needed for two reasons: 1) to restore the Ackerman steering geometry and 2) to make room between the tie rod and the axle for the panhard rod and power steering cylinder. Ackerman steering geometry is what causes the inner wheel to turn more than the outer wheel when making a turn. It is accomplished by drawing an imaginary line from the center of the king pin to the center of the rear axle, and ensuring the tie rode end lies on that line. Because the much wider brakes needed to be inset quite far, the steering arms had to go around the brake (easier to see in the upper right picture on the next page) in order for the tie rod end to lie on the imaginary line.

 

Tie Rod, Panhard Rod, Wishbone Ends, and Steering Mounts:


Tie rod mounting bosses made from 1" round stock for the tie rod, drag link, and panhard rod.


Driver's side steering arm with additional arm welded to it to connect the drag link


From top to bottom: 1) Model A front axle 2) panhard rod (modified 2013 Jeep Wrangler part) 3) Corvette power steering cylinder 4) fabricated tie rod.


Front end almost ready to go into the Model A. Note the spit wishbones behind the axle with tie rod ends fitted to them.

 

Idler Arm Bearing Mount, Wishbone Mount, Pedal Mount, and Steering Box:



The steering, pedals, and wishbone mounts all ended up needing to be mounted to the frame at the same place, so I fabricated this rather intricate mount. On the top is the steering idler arm bearing, to the right is the fabricated pedal mount bar, and below is a rubber insulated wishbone mounting point. Originally the pedals were mounted to the transmission, the wishbone mounted to the bottom of the bell housing, and there was no idler arm. But since I removed the original bell housing and transmission, I had to make this new mount.


Steering box sector shaft bushing housing. This two bolt flange was machined off and a new flange fabricated and welded to the housing to move the housing over 1-1/2" to clear the engine.


Although hard to see, the new flange was welded on in a position ~1-1/2" closer to the steering box, the frame was blistered on the bottom to allow the box to go inside the frame rail.

 

Steering Box and Linkage:


The machined steering box sector shaft bushing housing (being pointed to) now comes through the frame vice being bolted to the inside of the frame. A second plate was welded to the outside of the frame for added strength after "blistering" the bottom rail.


Final assembly, the steering box now comes through the frame rail, the pitman arm was shortened 2" and the modified stock drag link goes rearward to the idler arm and a 2nd draglink goes forward from the idler arm to the driver's side front wheel steering arm. The purpose of the idler arm was two fold, 1) allows the 2nd drag link pivot point to be in line with the wishbone's pivot point where it bolts to the frame - this is the mathematically correct position to avoid bump steer, and 2) hides the Corvette power steering control valve (mounted to the back end of the 2nd drag link) and hoses under the running board's splash apron to retain the Model A's stock appearance.

 

Shock Mounts:


The shinny piece is an aftermarket shock mount used to mount tubular "aircraft" style shocks to the Model A axle. However, I found out these cannot be used with the stock length perch bolts.
Incidentally, the term "aircraft" style shocks is a post-war hot rodding term. Shocks before the war, including Model A's, were lever arm shocks. The modern tubular ones used today seem to have been invented (or at least became popular for cars) shortly after the war.


Because I wanted to use the stock perch bolts, I cut the shock mounts and welded them to the outside of the lower axle mount pad.
Also shown at the rear of the split wishbone is a tie rod end with a threaded piece welded into the wishbone.

 

Chapter Three - The Rear Axle

After my cousin, who has worked on race cars and old cars his whole life, told me stock Model A rear axles don't hold up well at sustained speeds above 55 MPH, I did some research and he was, of course, correct. So a 1948 Ford axle, which looks the same as a Model A axle but beefier, was used. But the 1948 axle is considerably wider than the Model A so it had to be narrowed. Additionally, above some amount of increased horsepower and traction, Ford axle shafts from 1928 - 1948 are known to break, and when they do, the wheel comes off the car. So I bought a kit from Hotrod Works that allows the use of 1957 - 1986 Ford 9" axle shafts. The kit comes with the newer brake flanges and since I had a 1986 Ford E150 donor van with the post war style Bendix rear brakes, it made mounting the rear brakes an easy task.

All Fords from the 1909 Model T through 1948 used a torque tube rear suspension design in which the drive shaft is located inside a tube that connects the rear axle to the transmission. At the transmission there is a large ball and socket assembly that the torque tube, and hence the entire rear suspension, pivots on. Because I will be using a newer transmission there is no ball and socket assembly, hence there is no place to mount the stock torque tube. So it was replaced with an open drive shaft with a yoke kit from Hotrod Works. And the torque tube was replaced with a hand fabricated torque arm that goes to a ball and socket "Johnny Joint" from Currie Enterprises.

 

Machining the Ring Gear


To adapt 9" Ford axle shafts, the ring gear and differential have to be machined to accept the 9" Ford spider gears. Pictured here is a fixture to mount the ring gear in to ensure the new boss is concentric with the ring gear's main bearing.


Boring the ring gear to accept the 9" Ford spider gear.


I accidentally over-bored the gear due to me not appreciating the amount of tool flexing due to machining hardened steel. So I made a bushing to press into the ring gear to make the bore smaller.

 

Ring Gear and Housing Jigs:


new bushing pressed into ring gear and bored to the correct diameter for the 9" Ford spider gear.


9" Ford spider gear assembled in the ring gear. Of note, this is not a stock 9" Ford spider gear, it is a custom piece made by Hotrod Works for this conversion.


Homemade jig to press out the pinion and it's bearings.


Fabricating the jig to keep the correct bearing alignment when narrowing the axle housings. The jig is the piece inside the tube that is mounted to the lathe's head stock. I needed to cut a groove in the face of the jig, that would fit snugly on a boss (not shown) on the flange of the axle tube, but I didn't have any way to precisely measure the groove, so I did the cut a little and test fit, cut a little and test fit, method until the axle tube fit the jig with no radial slop. This is why the axle tube is also on the lathe, resting on Vee blocks and wood.

 

Axle Housing Jigs and Mock-up:


A closer view of turning the jig with the axle housing being used to test fit the groove. The jig is comprised of a 1/2" flat plate with a 1" thick square welded to the center and a 2" hole bored through it that creates a 0.001" interference fit with the 2" precision ground bar that used to be a ram from a hydraulic cylinder that I got out of a local dumpster for free.


The ring gear, differential, and 9" Ford axle shafts pre-assembled. Unfortunately, the guy sent me axles that were 1-1/2" too short. But he was able to get the correct axles made and shipped within one week - Thank you Hotrod Works!


Cutting the axle tubes to length.

 

Welding Axle Tube on Jig:


the finished jig.


an axle tube mounted on the jig with the new wheel bearing / brake flange housing tack welded to the axle tube. Note the aluminum puck that was fabricated to precisely align the wheel bearing housing to the jig's 2" diameter bar.


Assembled axle housing with the open driveshaft conversion installed on the pinion. The gear ratio is 4.11:1

 

Narrowing the Rear Spring:


Because the spring mounts to the top of the axle and the hydraulic brakes have the wheel cylinders on the top of the axle as well, the rear spring needed to be 4" narrower. The main leaf on the left is from a 1935 Ford and it is shorter when measured along the spring than the Model A spring shown on the right.


Cold bending the 1935 Ford spring a little at a time to match the Model A arch.


Model A spring in the rear, the re-arched 1935 Ford spring in front which is 4" narrower than Model A spring.

 

Spring Hangers, Brakes, and Alternator Bracket:


Boring the new spring hangers.


Axle assembled with brakes.


Alternator bracket from a kit for a 9" ford with an adapter piece I made to bolt the bracket intended for a 9" Ford to the 1948 axle's pinion bearing mount. Why put the alternator on the rear axle? It turns out the fan needs to be mounted to the generator to fit in the engine compartment correctly. Ford mounted the fans this way from 1932 - 1936. After which the fan was relocated to various places from 1937 - 1953 (the last year of the V8 Flathead). The generators from 1932 - 1936 have a double tapered roller bearing to absorb the axial thrust of the fan, latter generators, including the new 12 volt, 90 amp alternators that look like an original generator, do not have a roller thrust bearing and, per the manufacture for the new alternator and other research, these latter generators will fail if a fan is mounted to them. To keep with the stock looking theme, a 1932 - 1936 generator was used to mount the fan while a 12 volt modern alternator is hidden under the car mounted to the rear axle.




Rear Axle Assembled:

Spring mounted, fabricated torque arm mounted, modified 1935 Ford radius rods, and pulley welded to the drive shaft yoke to drive the alternator. At the front is the outside housing of the "Johnny Joint." These joints have urethane sockets to insulate the road vibration of the axle from the frame.


Using a spreader tool to spread the spring to mount on the axle. Notice the tool had to be narrowed as well due to narrowing the spring.

 

Chapter Four - The Engine

The stock Model A came with a four cylinder "L" head, commonly known as a flathead, engine that produced 40 Horse Power (HP). With "highway" gears in the rear axle, a stock Model A can attain 55 MPH maximum. To go 75+ something better is needed. A very popular early hotrodding engine swap entails putting a V8 Ford flathead into a Model A.

Ford made the V8 Flathead from 1932 - 1953 in 3 basic variants, 1932 - 1938 21-stud version, meaning 21 studs were used to bolt each head to the block, the 1938 - 1948 24-stud version with integral bell housing, and the 1949 - 1953 24-stud version without the integral bell housing.

The particular flathead I used was made sometime between 1938 and 1942. It originally displaced 221 cuin and produced 85 HP. The cylinders, valves, etc were in really good shape so I initially thought I could get away with a ring and bearing job...that was not to be the case. After measuring the cylinders, crankshaft, and camshaft, it was too worn out for a quick cheap rebuild. So I started researching stock replacement parts and was shocked by how expensive it is to rebuild a stock flathead, especially the pre-1949 versions. For not too much more money, I could buy performance parts in lieu of stock parts, so that is what we did.

The final engine displaces 281 cu in and produces about 160HP, double that of the stock V8 engine, but it looks stock, complete with a stock looking 2 barrel carburetor.

 

Boring the Engine Block

After finding out that the price difference between a stock rebuild and a high performance rebuild wasn't very much, I decided to go all out and build a very stout street engine. After being hot tanked and passing a magnaflux test, the next thing was to measure the cylinder wall thickness to find out how much the block could be overbored. Sonic checking showed the maximum overbore would be 0.030". However, to run an off the shelf stroker crank with off the self rods and pistons a 0.060" overbore was required. The results of the sonic measurements also showed the block experienced some core shift when it was cast, meaning the sand core for the water jackets and outside surfaces of the cylinder walls shifted such that all the cylinders were thick on one side and thinner on the other side. The block could be bored out 0.060" if the bores were offset such that more material was removed from the thick side than the thin side. The machine shop said they did not have the capability to offset bore cylinder blocks...so I decided to use my milling machine and do it myself.




Block on the mill, notice the 2"precision ground bar in the middle picture (also a hydraulic cylinder ram from a dumpster) used to locate the block in the mill. To locate the block on the bar, aluminum pucks, shown in the lower picture above, were made with an interference fit in the block and a 0.001" clearance fit on the bar.


Two cylinders done, 6 more to go!

 

Relieving and Porting the Block



While the block was in the mill, I relieved it, meaning, the block material between the valves and the cylinders was removed to promote air flow into the cylinder. This is an old hotrodding trick, but, like boring a block, something I've never done before.


This is the bore with the thinnest wall. For a ~400HP modern V8, the rule of thumb is to have a wall thickness no thinner than 0.090". This cylinder, the only one under 0.090", ended up being 0.084" at the center of travel. Since this engine will be far less than 400 HP, I think it will be fine. The untouched area near the top cleaned up nicely when the block was honed.


I also ported the block, meaning, the intake runners, pictured here, were made larger to promote air flow.

 

The Rotating Assembly


4.250" stroker crank from SCAT. Stock was 3.750".


SCAT H-beam rods, JE Forged pistons.


One of many hiccups during the build - the bottom is what a rod bearing is suppose to look like, the top is what the machine shop did to my brand new bearings when clearancing the block for the stroker crank - one of the few operations I had the machine shop do to save a little time.


Crank in block, main bearings installed, caps torqued and lockwired. This part of the installation was the only thing that did not give me problems. Nothing else went together right the first time either due to the machine shop, the camshaft grinder, or my lack of knowledge when it comes to the very unique Flathead Ford.

 

The Valve Train:


The first hiccup was the cam would not go through the front cam bearing. Apparently a modern cam bearing installation tool can not be used on a Flathead Ford, which is what I believe the machine shop used based on how the bearing was deformed. The installation tool has to be designed just for the Flathead. Pictured above is the cam bearing installation tool I made to remove the bearings the machine shop installed and install new cam bearings.

Notice the "How to Build a Supercharged Flathead Ford" book on the bench.







Measuring installed spring height turned out to be a challenge because of the limited space in the valve galley. After searching the internet revealed very little, I came up with this method: Measure the distance from the bottom of the guide to the retainer by measuring full range of valve motion, then add the distance from spring seat to retainer with the retainer against the guide to get the spring seat to retainer measurement when installed and the valve is closed.

 

Valves, Lifters, and Guides:


Above: undercut street flow Manley stainless steel exhaust valves for a small block Chevy. This is a very popular swap because the stems are the same diameter as the Flathead, they are larger than stock (1.6" vs the stock 1.5") and are far cheaper than Flathead valves. Additionally, they are 0.060" longer than the Ford valves, which should help when running a bigger cam that has a smaller base circle diameter.

Unfortunately, the retainer is 0.200" lower on the stem than the Ford. There are several ways to deal with this, the one I choose initially was to re-groove the stems, but after examining it more, I decided to make 0.200" thick spring shims.

Originally I had the stock cam reground by a well known shop, but the lifters were riding on the rough casting between lobes when on the base circle. Not sure why, but I was running out of time, so I ordered a brand new Iskenderian cam with their Max 1 grind (0.364" lift, 226 degrees at 0.50", 110 degree separation angle). Back in the day this would be considered a 3/4 race cam vice an all out competition race cam.



The 0.060" longer valve stems did not help in this engine, in fact, the cam, lifters, and valve combination would not physically fit in the engine. I had to modify all 16 lifters by counter sinking the tops 0.100" and bottom tapping them so the adjuster screw could go down enough so everything would fit.

Because the stems are longer and the lifter screw is lower in the lifter, setting the valve lash was problematic because the lifter cannot be adjusted when it is on the base circle, where valve lash is measured, because you can't get a wrench on the screw. So I tried a method of measuring the valve lash while pulling down on the valve guide, then releaseing the guide to move the lifter up the bore to adjust, then repeat. However, the many times of pulling down on the guides caused me to break one.

I finally figured out that you can adjust the lifters with a thin wrench with the springs and guides installed. Still have to move the lifter up to adjust it, but the screw will turn.

 

Heads and Final Assembly


Cylinder heads back from the machine shop.


Another hiccup - my fault this time. To make sure there was enough piston and valve to head clearance the process involves putting clay on the pistons and valves, bolt the heads on, rotate the crankshaft, remove the heads, then measure the thickness of the clay. What I didn't take into account was the clay is also squeezed between the pistons and cylinder walls. At this point in the build, the pistons, rings, rods, and bearings were final assembled, meaning, I had to take it all back apart again, clean out all the clay, and do a 2nd final assembly. Lesson learned: check this before final assembly, ie, with no rings and rods not torqued all the way.


Finally, the heads are ready to be bolted on with the copper head gaskets for the last time. At least that is what I thought at this stage, more to follow on that...

 

The Oil Pump:





Most engines until the 1950s only filtered a portion of the oil, the rest went straight to the bearings unfiltered. There are several options to modify the Ford Flathead so that all the oil goes through a modern, remotely mounted oil filter. But all of the typical ways it is done uses a stock oil pump. I bought a Melling high volume pump, so of course, I had to invent a new way to route the oil out of the block.

Top: First the oil pump was disassembled and the pump element discharge passage was tapped and a plug (seen below the drive gear) was inserted.

Middle: the pump cap, which is significantly different than the stock pump was drilled and tapped on the discharge side.

Bottom: the brass 3/8" pipe is threaded into the oil pump cap. The pipe goes through the oil pan and was sealed using a tube welded to the oil pan and a hose connecting the outside of the welded tube to the outside of the brass pipe.

However, the pipe exited the oil pan at the exact location where the two-piece oil pan is spot welded together. One piece is the pan that holds the oil, the other is a non-leak tight piece that forms the bottom of the bell housing. This would become a problem the first time we put oil in it and all the oil ran out onto the floor. A professional hot rod builder in Homestead spent several hours trying to seal it with a MIG welder - he did an awesome job working late into the night an he finally got it to be good enough for a hotrod.