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Old 07-12-2018, 11:17 AM   #21
Kohnke Rebabbitting
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Default Re: Rear main seal options - which one?

Originally Posted by Terry Burtz, Calif View Post

Thanks again for your comments.

Thanks also for your foresight by saving original Ford A-6335's.

I am happy that we are in agreement that the replacement A-6335's are junk and not compatible.

Can you post any experience where a seal was used with an original A-6335 and the instructions were followed including pressure testing?

Thanks, Terry Burtz

Yes, Sir., All.


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Old 07-12-2018, 12:18 PM   #22
steve hackel
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Default Re: Rear main seal options - which one?

Hello Terry & Herm; does this procedure hold true for the B' blocks in the same way as the A' ? If anything, what is different in parts, assembly & or machining? I have a B' block / engine, that is still not rebuilt and have considered this in the past. Thanks, Steve
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Old 07-12-2018, 01:26 PM   #23
Terry Burtz, Calif
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Default Re: Rear main seal options - which one?


Thanks for asking the question.

The "B" seal is a similar design, but different because the groove in the Model B rear main cap is different than the groove in an original B-6335 block insert. Dimensions are also different to fit the Model B engine.

The "B" seal contains 2 full circles. One fits the groove in the rear main cap, and the other fits an original Ford part #B-6335. Both circles need to be cut just slightly longer than half to provide a little crush at the parting line.

Dan Price makes a substitute for B-6335 that has a groove that matches the groove in the rear main cap. If the Dan Price insert is used, one seal circle is used by stretching it over the flywheel mounting flange and the other seal circle is discarded. Dan price can be reached at dan4banger.com

I have pasted the Model B Seal instructions below. I did not include the figure that shows a cross section of the rear main area. Please note that 2 different pressure checks are specified, one where the rear main drain tube is pressurized, and the other where the galley feeding the rear main bearing groove is pressurized.

1) Two seals are supplied. The larger seal fits into the groove of the rear main cap (B-6327), and the smaller seal fits into the groove of the block insert (B-6335). The smaller seal will not fit properly in a poorly made reproduction block insert.
2) If desired, a replacement block insert with a groove identical to rear main cap groove can be made or purchased. In this case, discard the smaller seal and upon assembly, lubricate and carefully slip the seal over the flywheel mounting flange. A plastic sandwich bag placed over the flange will protect the seal from damage due to small burrs.
3) Thoroughly clean the grooves in the rear main bearing cap (B-6327) and block insert (B-6335) to remove all traces of dirt and oil, which may interfere with proper seal installation and sealant adhesion. Also, make sure rear main cap drain pipe is clear
4) Seat each seal with lip pointing towards front of engine (see figure) into its respective groove, and trim the ends slightly long to provide “crush” at the mating surface. A single edge razor blade and stationary disk sander work well for trimming and squaring the ends. Cut the pieces to be used long, and experiment with trimming and squaring operations on the cut off pieces.
5) Without the crankshaft in place, assemble the seal with its lip facing towards front of engine, shims, block insert, and rear main cap to the engine. Check to be sure the seal fits properly in its grooves, and is not distorted or offset relative to the rear main bearing.
6) Machine the rear slinger area of crankshaft as shown in the figure. Finished diameter shall be between 2.330 in. and 2.370 in., and concentric with the rear main journal within .001 in. to prevent whipping of the seal lip outward. Machine crankshaft to largest diameter between limits consistent with cleanup. Polish seal contact area of crankshaft to a bright smooth finish. Main bearing clearance must be between .0010 in. and .0015 in. to keep the crankshaft from whipping the seal lip outward. On final assembly, apply either an RTV silicone adhesive or Permatex #2 sparingly to both grooves and all mating surfaces where shims, rear main cap, block insert, and block meet. Avoid getting adhesive on seal lip. Also apply sealant to rear main bolts.
7) Before installing oil pan, and after adhesive has cured, test seal and rear main cap area for leakage by pressurizing the rear main cap drain pipe with motor oil to 10 psi and check for leaks.
8) If a Model B engine that has been modified to provide pressure to the connecting rods (drilled crankshaft) is using this seal, an additional oil pressure check should be done by pressurizing the rear main bearing groove that supplies connecting rod #4 to the anticipated pressure (40 psi?). If a leak occurs, it will usually be between the groove in the rear main bearing feeding rod #4 and either thru the shims or up or down the rear main bolts.
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