Insert Main Bearings

Available for Model A and Model B

Insert bearings provide durable and stronger bearings for the engine. As we drive longer times at higher speed the demand for updating the Model A engine is an essential part of rebuilding. Tri-metal lined bearings designed for the Model A block have holes drilled with integral oil grooves to give more bearing surface with proper lubrication.

Notes:

  • Insert main and rod bearings work fine without any changes to oil system. Bearings work with or without pressure oil system.
  • Oil filter gives longer life but is not required. Change oil regularly with modern motor oil.
  • Contact oil seals are not necessary.
  • The block does require machining to install inserts the first time.
  • Available in STD, .010, .020, .030, .040, and 060 undersize.

Main Bearing Instructions

Model A

CRANKSHAFT MAIN JOURNAL SIZE STANDARD 1.6254/1.6259
CRANKSHAFT MAIN JOURNAL SIZE .002 UNDERSIZE *For Burlington Crank* 1.6234/1.6239
CRANKSHAFT MAIN JOURNAL SIZE .010 UNDERSIZE 1.6154/1.6159
CRANKSHAFT MAIN JOURNAL SIZE .020 UNDERSIZE 1.6054/1.6059
CRANKSHAFT MAIN JOURNAL SIZE .030 UNDERSIZE 1.5954/1.5959
CRANKSHAFT MAIN JOURNAL SIZE .040 UNDERSIZE 1.5854/1.5859
HOUSING BORE IN BLOCK 1.7705/1.7710

The back of the rear main bearing block and cap is to be counter bored .125 deep and 2.250 diameter.
The rear thrust washers are held in place by counter bore and crankshaft. The block thrust washer is to be doweled to the block to prevent rotating. Thrust washers are not to be attached or secured as this can cause end loading and abnormal wear.

The front of the rear main bearing block only is counter bored .125 deep and 2.250 diameter.
The front thrust washer is held in place by counter bore and crankshaft. The cap not counter bored will prevent the thrust washer from rotating. Again the thrust washer is not secured to the block.

We recommend the use of lined bearings with the model A crankshaft. Bearings are in stock at competitive pricing.

MAIN BEARINGS SET OF 6 FOR 1 BLOCK $93.50
THRUST WASHERS SET OF 3 FOR 1 BLOCK $38.14

Model B

CRANKSHAFT MAIN JOURNAL SIZE STANDARD 1.9990/1.9985
CRANKSHAFT MAIN JOURNAL SIZE .010 UNDERSIZE 1.9890/1.9885
CRANKSHAFT MAIN JOURNAL SIZE .020 UNDERSIZE 1.9790/1.9785
CRANKSHAFT MAIN JOURNAL SIZE .030 UNDERSIZE 1.9690/1.9685
CRANKSHAFT MAIN JOURNAL SIZE .040 UNDERSIZE 1.9590/1.9585
CRANKSHAFT MAIN JOURNAL SIZE .060 UNDERSIZE 1.9390/1.9385
HOUSING BORE IN BLOCK 2.1350/2.1345

The back of the rear main bearing block and cap is to be counter bored .125 deep and 2.875 diameter. The rear thrust washers are held in place by counter bore and crankshaft. The block thrust washer is to be doweled to the block to prevent rotating. Thrust washers are not to be attached or secured as this can cause end loading and abnormal wear.

The front of the rear main bearing block only is counter bored .125 deep and 2.875 diameter. The front thrust washer is held in place by counter bore and crankshaft. The cap not counter bored will prevent the thrust washer from rotating. Again the thrust washer is not secured to the block.

We recommend the use of lined bearings with the model B crankshaft. Bearings are in stock at competitive pricing.

MAIN BEARINGS SET OF 6 FOR 1 BLOCK $ 99.00
THRUST WASHERS SET OF 3 FOR 1 BLOCK $ 38.14

The block and caps installed with no shims will require align boring. The housing bore in block is to be 1.7705/1.7710. the finish 60-90 mico inches ra.

The back of the rear main bearing block and cap portions are to be counter bored 2.250 OD and .125 deep. Now remove cap and counter bore block only on front of rear main 2.250 OD and 125 deep.

Remove all caps and cut slots in block and caps for aligning lugs.

Place bearings in block and caps check that aligning lugs and oil holes fit correctly. Some blocks, mainly early 28, may require elongating oil holes in bearings. 80 percent alignment is good.

Fit thrust washers in block and cap. Now file any portion that extends higher than parting line. File large bevel on both edges of front thrust washer 1 only (the contact face of crankshaft thrust) A square edge will cause oil to be wiped from crankshaft. On the back of the rear main it recommended to use 2 thrust washers and 1 of the washers should be doweled to block or cap to prevent rotating. The counter bore holds washers in place, crankshaft keeps them in position. The dowel keeps the rear from rotating and the cap keeps front from rotating. Thrust washers are not to be secured to block or cap as this can cause end loading and premature wear. I recommend a small amount of RTV sealer be used on outside edges of rear main cap to prevent leaks.