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Tests the Ford Model ‘A’ Ford Engine

Tests the Ford Model ‘A’ Ford Engine

By BZR 0 Comment August 16, 2019

I wanted to find out how the engines I rebuild compare to a stock Model “A” engine. I decided that dynamometer testing would best show the improvements made to the engine.

The tests were done on a Super Flow 901 Dynamometer. It is a computer machine and is calibrated on a yearly basis.

Testing on the dyno is done at full throttle. The computer increases the load until it brings the RPM to a lower preset limit to start the test cycle. When the test cycle is started the computer eases the load to allow the RPM to increase. It then takes measurements at preset intervals until it reaches the upper preset RPM limit and then returns the engine to the lower limit. That completes the test cycle.

For these tests I needed an engine that was as near to stock as I could find in order to set a reliable base line from which to measure any improvements. I borrowed an engine from a past customer who had removed a rebuilt stock engine with only 2000 miles on it. This engine was in good condition and had been sleeved back to standard bore. The valve train was rebuilt using reproduction stock parts. The camshaft had been re-ground with a stock “A” grind. The crankshaft and flywheel were stock. This was what I needed for a base line comparison, a basic stock engine with no modifications.

This engine will be referred to as Engine #1.

I rebuilt two more engines for comparison testing at the same time. Engine #2 was rebuilt with insert bearings and my preferred parts list. Engine #3 was also rebuilt with inserts, but was stroked .360″.

Engine #2 was rebuilt using parts and services that I have found over time to work very well together in a Model “A” block. The engine had insert bearings in the rods and mains and a counter weighted crankshaft. It was dynamically balanced and had a lightened flywheel with a harmonic dampener installed. The pistons were from a Ford 351 ci V-8, which required a 4″ bore. The valves were from a GMC truck with one piece valve guides from a Buick. The engine had a mild performance camshaft and the ports were enlarged and polished.

Actually engine #3 is a teaser, because we will tell it’s story in the next issue. The #3 engine had been stroked by offset grinding the rod journals on a Model “B” crankshaft by .180″, which achieved a stroke of 4.610″ verses the stock Model “A” stroke of 4.250″. The engine had a pressurized oil system and I installed a Chevy 350 rear main oil seal. The block was bored to .06″ over standard (3-15/16″) and used 283 ci Chevy pistons. The engine had an aluminum Clings Aftermarket Products (Tempe, AZ) flywheel. The entire unit was dynamically balanced and had the same valve train and camshaft as engine #2.

I also wanted to test some other bolt-on items such as: heads, distributors, carburetors, spark plugs, mufflers, fans and fan belts. I wanted to see how these things compared to the stock Ford equipment.

Photo caption:
Stock Model “A” on the dynamometer. This carefully rebuilt, completely stock Ford Model “A” engine produced only 35.6 HP @ 2250 RPM!

Cylinder Heads
I tested four heads: A stock 4.2:1 compression ratio Model “A”, a stock 193 Model “B” head with letter “C” cast in the top, a Brumfield reproduction 5.9:1 high compression head and a Dan Price Reproduction Thomas with a 7:1 CR. These heads were chosen due to their ready availability and common use.

For distributors I chose the stock Model “A” unit for the base line and the dual point Mallory because of its quality, adjustable timing advance ranges and easy availability.

Manifolds & Carbs
On each engine I used stock manifolds and a Zenith carburetor, again to establish the proper base line. Then I installed a Weber progressive 2 barrel carburetor fitted to an aluminum single down draft manifold. I chose these because my customers reported excellent results and because these items are easily obtainable new. Pete Westler of Auto Care and Restoration (Redding, CA) agreed to furnish these parts for the test.

Spark Plugs
Several brands of plugs were used. Please refer to the test charts for the specific plugs I settled on for each test. There was only one set of plugs in which I was severely disappointed. Spitfire brand plugs actually caused the engines in this test to lose two horse power. Their ads claim that these plugs will produce more power. I did not see that at all.

Mufflers, Fans & Belts
For the base line we used a standard reproduction muffler and compared it to an Aires brand muffler. The fans I used were: Stock two blade original Ford fan, a six bladed fan available from several new parts dealers and a six blade fan from Clings. The fan belts tested were: a 5/8″ stock V-belt and a 5 groove serpentine belt and pulley set available from Clings.

The Testing – Test #1:
The engine was Ford stock right down to the 3-X Champion spark plugs.

Tests the Ford Model 'A' Ford Engine

Notes: Notice the torque jump around and the steady HP increase, but where is the 40 HP that Ford claimed? The best results were obtained using 31 degrees of timing advance.

Test #2:
Changed to a Mallory Dual Point distributor. timing was set at 15 degrees at 700 RPM and full advance of 31 degrees at 2000 RPM. Out of the box the Mallory had a preset range of 16 degrees when I received it.

Notes: The torque and HP increased at lower RPM.

Test #3
Replaced the stock intake/carb with the new Weber and manifold set.

Notes: Watch the torque/HP/airflow changes. When the Weber carb, intake and header set up was installed the gain was 7 HP. That is equal to a 20% gain in power. The torque also improved and remained flat all the way to 2000 RPM. At 2000 RPM the torque peaks. This shows the limitations of the stock camshaft grind and valve train. The CFM at this point is only about 10 CFM more than in test #2.

The engine reaches 35 HP at the air flow of 63 CFM with both carburetors; The Zenith at 2000 RPM and the Weber at 1750. This is sign that the Zenith is reaching its limit. With the Zenith set up, it is harder to breath and doesn’t develop as much torque as with the Weber carb and new intake manifold.

Tests 4-13 were run with engine #2. This engine had a mild cam and the intake ports were enlarged at the valve seat to 1-7/16″ and polished. The block was bored to 4″, the pistons were from a Ford 351 ci V-8 and they had 1/16″ offset at the wrist pins which improves torque.

Test #4:
Engine # 2 with a stock carb, manifolds and head that measured out to 4.1:1 CR, but actually was 4.5:1 with a 4″ bore. I added a Mallory with timing at 5 degrees at 700 RPM to 30 degrees at 2250 RPM. Spark plugs were Champion C16C.

Notes: Look at the significant HP and torque changes between the stock engine #1 in test #2 and engine #2 in test #4. There is a 15 HP increase or 43% more power than the stock #1 engine and 35% more torque at 2000 RPM.

Test #5
Engine #2 with Weber, intake and tube header set.

Notes: Look at the significant HP and torque changes between the stock engine #1 in test #2 and engine #2 in test #4. There is a 15 HP increase or 43% more power than the stock #1 engine and 35% more torque at 2000 RPM.

Test #6:
Changed to a stock 1932 Model “B” head and back to a stock intake/ exhaust manifold, Zenith carb and new Mallory with the timing set to O degrees to 25 degrees. Compression measured 5.4:1 with the 4″ bore and a slight amount of milling.

Notes: Compare the peak HP in tests # 2, #4 and #6. The compression moved up almost a full point (.9:1) and only gained 3 HP. Torque gains were also small.

Test #7:
Changed back to the Weber, intake and header set up.

Notes: Peaked at 68 HP, which is a 96% increase over test #2 and 63% increase over test #3. The Weber set up is now worth 15 HP of BOLT ON POWER!!

Test #8:
Changed to the Brumfield 5.9:1 head (actually 6.2:1 with the big 4″ bore), Stock manifolds, Zenith carb and Mallory with timing set at 6 degrees to 31 degrees.

Notes: Compare the differences in CFM in Test #8 and Test #6:

In comparing the CFM between two different heads, using the same carb and manifolds; it shows which head is more efficient in the airflow category. It’s beginning to appear that compression is less important than airflow to the performance of an engine.

Test #9:
Changed to Weber carb, intake and headers.

Notes: Weber carb, intake and header set made a 13 HP (22%) improvement over the stock carb and manifolds. Test # 9 shows 102% more HP than test #2. Notice the torque peak of 151 lbs./ft. at 2250 RPM and the peak in airflow of 105.2 CFM at 3000 RPM.

For the next series of tests (#10-#13) I changed to the Thomas 7:1 CR head. This head has a 1/8″ relief or “fly cut” milled in it for piston clearance. The resulting CR is still 7:1 due to the 4″ bore. The Mallory, Weber, Intake and headers set was used all four tests. These tests show the progression of improvements as different spark plugs, timing settings and fuel are tried.

Test # 10: Timing was set to 6 degrees to 31 degrees. NGK (BPR6ES) spark plugs.

Test # 11: Timing was set 0 degrees to 25 degrees.

Test # 12:
Changed to AC spark plugs (R45XLS).

Test # 13:
Changed to Super unleaded gasoline:

Notes: The Thomas head had very strong torque improvement in the 1000 to 2000 RPM range, which is your normal driving range. But at higher RPM ranges (2000 to 2500), the torque really starts to drop off considerably. Note the CFM of the Thomas head at 2500 RPM on all four tests. Compare these to the Brumfield head. At 2500 RPM the B-F has a better airflow of 97.3 CFM. The Thomas has the potential of producing more power if the airflow can be improved around the intake valve.

Muffler Tests:
Engine #1 was set up stock as in test #1 for the muffler testing. I first ran a base line test using the building’s exhaust system, which is a 6′ tube about 15′ long. I then ran tests of the ARIES brand and the standard reproduction mufflers. The differences in the three test results were insignificant.

Engine #2 was then set up for the same test with the 1932 head, stock manifolds, carburetor and a Mallory distributor. I first ran a base line using the house exhaust system. The base line results were 50.3 HP and torque of 117.3 LBS/FT at 2250 RPM. The Aries muffler test results were 52.2 HP and torque of 121.8 LBS at 2250 RPM. The standard repro version produced 48.4 HP and torque of 113.0 LBS/FT at 2250 RPM.

The Aries unit increased power by 1.9 or 3.7% when compared to the base line. The standard muffler caused a loss of 1.9 HP. The Aries muffler, compared to the standard repro, produced 3.8 HP more or a nice 7.8% increase.

The mufflers had no effect on engine #1 because of the stock valve train. As performance of the Model “A” engine is increased the exhaust pressure changes and the stock muffler can no longer handle the increases, causing a HP loss. Apparently the type of back pressure made by the Aries is beneficial to a modified Model “A” engine.

Fan belts & Fans:
Engine #2 was used with a stock carb, manifolds and head. The Mallory distributor was used and I changed to a Model “A” generator because of the serpentine belt and pulley set. Note that the base line test is slightly different from test #4 due to the alternator/generator change over.

Serpentine belt wins that one!

All four heads that were tested did run well, but take note that bigger torque and HP gains were achieved from improving airflow and not increasing compression.

Of these four heads, my choice for a strong running tour car would be the Brumfield. You can bolt it on straight out of the box with no modifications. It performs well on the highway as well as in town. The B-F also has no negative effect on the idle and runs smoothly. It would be less damaging to the crankshaft and bearings than some other new or old high compression heads.

With the Thomas head you will notice some low end vibration due to high torque and low RPM. The B-F head has a more even power curve than the Thomas. After running all these tests I feel that I have been told “The Big Lie” about how compression is the main HP increaser. The gains in power were smaller from compression increases and much greater from airflow improvements.

My goal was to find out what worked well on these engines and have the data to back it up. l ran over 150 tests. The results shown in this article are only the tip of the iceberg. I also ran tests with my #3 stroked engine. These tests will be published later. Thanks to Pete Westler for furnishing his Weber carb, intake manifold and tube headers.

And Guys, We sell a range of vintage lamps for automobiles and motorcycles. These lamps include the original carbide lamps and acetylene generators used on veteran and vintage cars and motorcycles. We also sell a range of oil side lamps and tail lamps with white 9004 led bulbs that were used on the Model T Ford and other automobiles of the era. Come to buy Here.

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