My 86 C20 5.7L is leaking oil BIG Time.

[1970pelle]

I'm using 3 qts a week depending on how much I drive the truck. I'm trying to keep it at a minimum till spring break. I won't need the truck while my boys are out of school. And will have some help also. I'm leaking out the rear main seal area, it appears. The flex plate and torque converter are cover with oil. And I have a river of oil running down from the back of the right side cylinder head. So head gaskets will need replaced. And I'm blowing a cloud of blue smoke at start up after setting for awhile. Valve stem oil seals.

My thousand dollar question is my truck is a 1986 5.7 with perimeter bolt valve covers. Do I have a two piece rear main seal or a one piece ? Is there a way to find out before removing the oil pan. I don't want to waste time dropping the pan to find out I have a one piece seal. Then turn around and have to pull the engine. I would much rather pull the engine. And do a engine bay cleaning and repaint.

With the part numbers on the right side deck of the block give me the info needed ?

Thanks Ken

[RUN GMC]

Read this on another site....I will provide the link............

I have an 85 k-10 305. I have oil pan and pump off how do I tell if it has a 1 or 2 piece rear main seal?

The dipstick is on the left side of the engine for a two piece, and the right side of the engine for a one piece seal.
The one piece goes on over the back of the crank shaft to replace it.
The two piece you need to remove the rear main bearing cap to replace it.

http://forum.73-87chevytrucks.com/sm...?topic=22760.0

[1970pelle]

I replaced many rear main seals in my 54 years. Looks like it coming out, dip stick is on the right. No worry's, I'll just detail the engine bay while apart.

Thanks Ken

[ZacharyDouglas1992]

one way to be absolutely sure (as older heads could have been put on a newer block, etc...) I would use the casting number on the engine. Here's a link to where you can look that up.
SBC CASTING #s

Of course if it is leaking as bad as you're saying, and you plan on doing head gaskets, it may not be much more work to remove the motor anyhow. Depending on the equipment/help you have at your disposal.

[ZacharyDouglas1992]

oops looks like you already decided. No matter, maybe that link will help someone else haha.

You may consider having the heads machined if you're going to have to do the seals for the valves. I did with my 87 r10 and definitely glad I did while I already had the heads off.

[geezer#99]

You don't get oil leaks from head gaskets. Water leaks but not oil.
I'd clean it off spotless, make sure the pcv system is working and fix the oil leaks you find up top of the motor.
Might not even be the rear main leaking.

[1970pelle]

Depending on the condition of the heads, I can do just about all the head work here at the house. Also with the nice weather here finally. I'll pull the oily mess outside the garage on the pad to keep trashing my garage floor.


Ken