The Ford Barn - View Single Post - Rear main seal options

Terry Burtz, Calif · 07-11-2018, 10:50 PM

Herm,

Thanks for the reply.

This is the first time that I have heard the term "Bubble Up", however I know what you mean.

The seal is designed to fit the groove in Ford part #A-6335 and does not need to be trimmed.

Replacements for A-6335 have different grooves and the directions for the seals state that they are incompatible. I pasted the instructions below. See instruction 2 below where it states "Most reproduction block inserts have a groove that is not compatible with this seal".

Original Ford parts (A-6335) are not hard to find.

Any rebuilder that scraps a cylinder block should remove A-6335 before scrapping.

1) Thoroughly clean the grooves in the rear main bearing cap (A-6327) and block insert (A-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.
2) 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. The seal is designed to fit snugly into the original block insert (A-6335). Most reproduction block inserts have a groove that is not compatible with this seal.
3) Machine the rear slinger area of crankshaft as shown in the figure. Finished diameter shall be between 2.090 in. and 2.150 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.
4) Deburr the flywheel mounting flange. Apply some grease to the seal contact area. Carefully and without stretching it more than necessary, lubricate and slip the seal with lip facing towards front of engine over the flywheel mounting flange. A plastic sandwich bag placed over the flywheel mounting flange will protect the seal lip from damage due to small burrs, and a small blunt screwdriver may be required to ease seal over flange.
5) 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.
6) 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 at least 10 psi and check for leaks. The seal will withstand 50 psi, however the sealant may fail at this pressure.

07-11-2018, 10:50 PM	#18
Terry Burtz, Calif Senior Member Join Date: May 2010 Location: Campbell,CA, USA Posts: 319	Re: Rear main seal options - which one? Herm, Thanks for the reply. This is the first time that I have heard the term "Bubble Up", however I know what you mean. The seal is designed to fit the groove in Ford part #A-6335 and does not need to be trimmed. Replacements for A-6335 have different grooves and the directions for the seals state that they are incompatible. I pasted the instructions below. See instruction 2 below where it states "Most reproduction block inserts have a groove that is not compatible with this seal". Original Ford parts (A-6335) are not hard to find. Any rebuilder that scraps a cylinder block should remove A-6335 before scrapping. 1) Thoroughly clean the grooves in the rear main bearing cap (A-6327) and block insert (A-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. 2) 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. The seal is designed to fit snugly into the original block insert (A-6335). Most reproduction block inserts have a groove that is not compatible with this seal. 3) Machine the rear slinger area of crankshaft as shown in the figure. Finished diameter shall be between 2.090 in. and 2.150 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. 4) Deburr the flywheel mounting flange. Apply some grease to the seal contact area. Carefully and without stretching it more than necessary, lubricate and slip the seal with lip facing towards front of engine over the flywheel mounting flange. A plastic sandwich bag placed over the flywheel mounting flange will protect the seal lip from damage due to small burrs, and a small blunt screwdriver may be required to ease seal over flange. 5) 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. 6) 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 at least 10 psi and check for leaks. The seal will withstand 50 psi, however the sealant may fail at this pressure.