Rear Main Seal Replacement
by Bill Schroeder
The rear main seal leak among small block owners is a very common problem. From my poking aroung on
the discussion boards I found out many owners with this do not fix it as they seem to know it's
difficult to eliminate (some say a poor design). I asked others in our tech session of 15 small
block owners if their rear seal leaked and many replied they have a leak. The service manual does
a pretty good job with this procedure, but
leaves off the discription concerning the removal of the "obstacles in the way".
The manual definately does not paint a clear picture in your minds eye of the proper use
of the installation tool. Nor does it have pictures of the way the tool is positioned and used.
My focus in this article is to describe to you more in detail (and show you the pictures)
of the installation of this seal.
Being that mine leaks as well, I took diligent notes and photos at this tech session with the
Adirondack Chapter of the NCRS. Many thanks to Brian
Cantele the Judging Chairman - he did a spectacular presentation.
So lets get started --- you will need a
Felpro Rear Main Seal kit -- a double offset lip seal
Part no. BS11829-1 (fits 1959-1985)
And a Oil pan gasket kit --- your choice -- one piece or a 4 piece cork whatever -- your preference.
When I asked the "motor heads" there was no unamomous agreement as to a particular type.
We used a Parragon reproduction gasket set.
Drain the oil 3 weeks in advance as you don't even need the dripping on your head during
Idler arm attached ---(click to enlarge)
Remove the bolts that attach the idler arm to the frame this allows the steering linkage to "drop"
(you do not have to re-align the front end)
Idler arm detached ---
Now you suficient room for the oil pan to pass the steering linkage
Now remove the starter
The lower center pan brackets that hold the plug wires have to be removed -
Loosen both shields and move them away from the oil pan
Now the oil pan can be loostened and removed -( break the pan seal gently with a screwdriver)
Remove the oil pump
Oil Pump ---
Now remove the rear main cap and with a small hammer and screwdriver tap on the edge of the seal,
The seal will protrude just enough so you can grasp it with needle nose pliers
Just for jollies pull the rod cap off one piston and check it out for abnormal wear patterns
I'm not going to tell you what you have to do if you see damaged bearings.......
Clean up the front seal area of the pan and the bearing cap etc. (we like laquer thinner)
Coat the lip seals with light motor oil - KEEP IT OFF THE MATING ENDS -
In your Felpro package you will find a small installation tool
this tool acts like a "shoehorn" to allow the seal to slide in its cavity without damaging it
Seal Kit ---
Position the tip of the tool between the crankshaft and the seal seat in cylinder case
position the seal between the crankshaft and the tip of the tool so the seal bead contacts
the tip of the tool
Top Seal Install ---
Be sure the lip seal is positioned towards the front of the engine
this seal CAN easily be installed backwards - all mating surfaces should be clean and free of oil
(NOTICE THE DESIGN: oil pressure is exerted against the lip forcing it to seal)
Use a 3/8 inch offset so the bearing cap parting line does not line up with the seal parting line
simply push seal up in clyinder case 3/8 inch - this offset will be on the bearing cap as well
Roll the seal around crankshaft using the tool as a "shoehorn"
Install the other seal half in the bearing cap
Apply sealant (we like Permatex Ultra Copper High Temp RTV Silicone Part No. 81878)
to the bearing cap to case interface, keep the RTV off the seal split line (only on the cap mating surface next to the seal)
Install the rear main cap and torque to specs.
RTV area on rear main cap (Error in the picture NO RTV on the blue seal)
Another picture to stop any confusion