Model A & B

Ford Garage

AER Insert Main Bearings & Bronze Thrust Washers

Installation Data & Instructions

This page details the installation instructions of the main bearing inserts produced specifically for Model A & B Ford engines by Rich Fallucca at Antique Engine Rebuilding (AER).

These modern insert bearing shells are specifically engineered for the Model A and B engine and are not an adaptation of an existing bearing from another application. The bearing shells are steel backed and have modern aluminum (not Babbitt) bearing surfaces.

The insert bearings are manufactured for AER to precise dimensions by an OEM engine bearing company. The block, caps, and crankshaft are required to be prepared and sized to precise dimensions to receive the bearings. See the table and information below for AER's recommendations.

Model A:
Finished Journal
Min / Max
AER Bearing
Set Number
Block & Cap Bore
Diameter & Finish
60-90 µin Ra
Min / Max
1.6254 / 1.6259 A Standard 1.7705 / 1.7710
1.6234 / 1.6239 A 002 Under 1.7705 / 1.7710 For new Burlington, and NOS Ford A crankshafts
1.6154 / 1.6159 A 010 Under 1.7705 / 1.7710
1.6054 / 1.6059 A 020 Under 1.7705 / 1.7710
1.5954 / 1.5959 A 030 Under 1.7705 / 1.7710
1.5854 / 1.5859 A 040 Under 1.7705 / 1.7710
1.5654 / 1.5659 A 060 Under 1.7705 / 1.7710
Model B:
Finished Journal
Min / Max
AER Bearing
Set Number
Block & Cap Bore
Diameter & Finish
60-90 µin Ra
Min / Max
1.9985 / 1.9990 B Standard 2.1345 / 2.1350 For NOS Ford B crankshafts
1.9885 / 1.9890 B 010 Under 2.1345 / 2.1350
1.9785 / 1.9790 B 020 Under 2.1345 / 2.1350
1.9685 / 1.9690 B 030 Under 2.1345 / 2.1350
1.9585 / 1.9590 B 040 Under 2.1345 / 2.1350
1.9385 / 1.9390 B 060 Under 2.1345 / 2.1350

Dave Gerold ( of Jordan, Minnesota has considerable experience rebuilding over 150 engines using these AER main bearing inserts and has posted some valuable experience on internet message boards.

Dave's personal views and experiences are included here for the reader's consideration.

Though the correct running clearance for the main bearings is 0.00175" per AER's recommendations, Dave has slightly different recommendations. Dave has stated that the AER recommended clearance did not work well for him on the rear main bearings when AER switched the final surface of the insert shells from Trimetal Steel-Copper-Lead/Tin to Bimetal Steel-Aluminum, as currently produced.

Dave has related the following failure mode he has experienced with the aluminum-faced insert shells welding themselves to the crankshaft. The bearing to shaft clearance was likely too little and it was the lack of oil that heated up the surfaces to the point of rubbing and melting the bearing material to the crankshaft. The spinning of the insert in the block housing bore was the last thing that occurred as the engine locked up.

Dave has found that the aluminum lined rear main insert should have 0.002" to 0.0022" clearance to be reliable, (meaning no lock-up) and to be leak free. He now hones the rear main bearing shells precisely using a honing mandrel and process recommended by Sunnen to increase the clearance for oil on the aluminum-faced insert.

The front and center main bearings can be finished at 0.00175" clearance and not create issues with running too tight.

The best clearance for all three journals is 0.002" per Dave's posted comments.

Block and Bearing Cap Bronze Thrust Washers

Additionally, Rich Fallucca supplies machined bronze thrust washers which are designed to work with his bearing inserts. They can also be used in place of the original cast and machined Babbitt thrusts of the rear main journal when using Babbitt bearings.

These bronze thrust washer sets can be fitted to the rear main bearing block saddle and bearing cap when using Babbitt bearings, and are recommended for use with modern insert bearing shells. The same block and cap preparation for the bronze thrust washers is required for either application.

Model A Insert Main Bearings (6 piece set) $85.00
Model A Bronze Thrust Washers (3 piece set) $27.00
Model B Insert Main Bearings (6 piece set) $90.00
Model B Bronze Thrust Washers (3 piece set) $30.00

To purchase insert bearing sets, bronze thrust washer sets, or complete engine rebuilding services, contact:
Rich Fallucca
4835 Louise
Skokie, Illinois 60077
(847) 674-6716

Model A Block and Bearing Cap Preparation Instructions

The block and bearing caps are to be assembled using no shims, then align bored, finished, and prepared to receive the main bearing inserts and bronze thrust washers.

Some blocks, mainly early 1928, may require elongating the oil feed holes in the block to align with the oil holes in the insert bearing shell.

Model A Block and Cap Preparation:
  1. Carefully inspect the main bearing caps and the block mating surfaces for damage or disruption. Ensure the caps fit precisely to the block surface without wobble, gap, or variation.
  2. Mark and identify the front and center main bearing caps for repeatable location and orientation on the block. The chosen cap, position, and orientation should be maintained throughout all machining and subsequent assembly and future service procedures.
  3. Assemble the main bearing caps to the block with no shims.
  4. Align bore and hone the block and bearing caps to the size and finish indicated in the table above.
  5. Remove all caps and cut slots in the block bearing saddles and bearing caps for the aligning lugs on the insert bearing shells. Confirm the alignment of the oil supply passage in the block with the oil feed hole in the insert bearing shell before cutting the block relief for the aligning lugs.
  6. Place bearing inserts in the block saddles and caps, and check that the aligning lugs and oil holes fit and align correctly.
  7. Using Prussian Blue, there should be at least 80% contact of the bluing on all bearing inserts to the block and caps.
  8. Counterbore the rear of the block rear main bearing saddle and bearing cap 2.250 inch OD (2.875 inch OD for Model B) and 0.125 inches deep to receive two semi-circular bronze thrust washers.
  9. Remove the rear main cap and counterbore the front (only) of the rear main saddle in the block for a single thrust washer.
  10. It is recommended to use two thrust washers on the back of the rear main, and one of the washers should be dowel-located to the block or cap to prevent rotation.
  11. The counterbore holds the two rear thrust washers in place, and the crankshaft keeps them in position.
  12. The dowel keeps the rear thrust washers from rotating, and the cap keeps the single front thrust washer from rotating.
  13. Thrust washers are not to be rigidly secured or attached to the block or cap as this can cause end loading and premature wear.
  14. Fit the thrust washers in the block and rear bearing cap.
  15. File any portion of the thrust washer that extends beyond the block-to-cap parting line.
  16. File a large bevel on both edges of the front thrust washer only (the contact face of crankshaft thrust). Leaving a square edge on the thrust would cause oil to be wiped from the crankshaft.
  17. A small amount of RTV sealer is recommended to be used on the outside edges of the rear main cap to prevent oil leaks at the rear.

Model B Block and Bearing Cap Preparation Instructions

The Model B instructions are the same as for the Model A, except for the larger diameters of the bronze thrust washers and the bearing inserts. Refer to the Model B table above for block and cap bore sizes.

The rear of the Model B block rear main bearing saddle and cap are both to be counterbored 2.8750 inch OD and 0.125 inches deep for two bronze thrust washers.

Remove the rear main cap and counterbore the front of the Model B rear main saddle (only) in the block 2.8750 inch OD and 0.125 inches deep for a single bronze thrust washer.

Shown above is a 1932 Model B counterweighted crankshaft and a Starrett V-Anvil micrometer. This type of three-point micrometer is designed to measure shaft diameters very accurately and repeatably, compared to other tools such as conventional micrometers or vernier/digital calipers.

Visit the links below on Ford Garage for more information about establishing and maintaining proper crankshaft and camshaft timing gear engagement and clearances.

More related information on Ford Garage:

  1. For more Model A & B related information, use the Site Search box at the top or bottom of this page.
  2. Model A Burlington Forged Counterweighted Crankshaft
  3. Model BB Ford-Köln G28T-6303-B2 Counterweighted Crankshaft  
  4. Model A & B Proper Crankshaft and Camshaft Positioning
  5. Model A & B Camshaft to Crankshaft Gear Alignment
  6. Model A & B Kwik-Way LBM Main Bearing Boring Bar Fixtures
  7. Model A & B Tobin-Arp Main Bearing Boring Bar Fixtures
  8. Model A & B LEMPCO FSU Main Bearing Line Boring Machine

April 2017