How can you tell if you have a one or 2 piece rear main seal on an 86 corvette? (Short of taking the transmission off to check) I know some earlier engines used the 2 piece while the later ones used a one piece.

 

I believe that if you can ID the information right side of block forward of cylinder head you can confirm the originality of your engine build. Along with probably the VIN Derivative you should find ZJH, ZKA, ZKD, ZJS or ZJW. Do you have aluminum cylinder heads?

 

If the car is an automatic, remove the metal pan under the torque converter and rotate the engine by hand while watching for a welded-on counter-weight to be present on the front side of the flex plate. If present, it is a 1-piece rear main seal. If not present, it is a 2-piece rear main seal. IIRC, the counterweight 'surrounds' one of the torque converter bolts.

For a manual trans, remove the front bell housing cover and observe the type of metal just above the rear 'loop' of the oil pan that the gasket fits into. A 1-piece seal has an aluminum seal retainer that bolts to the block and receives the oil pan gasket. A 2-piece seal, the material is the cast iron of the rear main bearing cap, which receives the oil pan gasket, and holds the lower half of the rear seal.

For either transmission type: The rear flange of the crankshaft on a 2-piece seal is never "round". It will at a minimum usually have a 'notch' out of its circumference, and many times may even be rectangular. A 1-piece seal rear flange is always perfectly round because the seal must install over the end of the crank. This can also be observed by rotating the crank.

 

I don’t think I have aluminum heads

 

If it is a Convertible, it has aluminum heads. If it is a Coupe built prior to about March-April 86, it probably has iron heads.

Iron heads have 4 valve cover bolts on the perimeter. 2 on the upper 'rail', 2 on the lower.
Aluminum heads have 4 valve cover bolts down the center of the valve cover, through the top surface.

I don't think iron or aluminum heads have influence on the type of crankshaft seal used in 1986. 1986 is first year of 1-piece seal, and last year for flat tappet camshaft lifters. Unless the engine has been changed in the intervening 38 years, which is possible.

WVZR gave you the engine codes for 1986, although it is very difficult to observe them through the accessories on a 84-87 unless you know exactly what you are looking for, and where you need to look to find them. And even then, the pad is generally way too dirty, greasy, or rusty to read without cleaning, which is tough with everything in place.

 

ok that means I definitely have the iron heads because my valve cover bolts are around the perimeter.

my only gripe with it being a one piece seal (and I kinda hope it is) is that all the parts stores i go to only pull up the 2 piece in their system.


This is exactly my problem I don’t know the exact place I need to look and it is all covered in grime anyways.

 

I just checked my door tag- I should have done this in the first place.. it says the manufacture date is December of 85 so definitely is an earlier one. This being known would the engine still be the 2 piece because it was built before 86 or would the one piece seal still be implemented?

 

I believe that 'all' '86 MY(Model Year) regardless of the build date will be 1 piece rear main. You've been told how to 'verify' so I'd say the rest is up to you.

 

All 86s have the 1 piece rear main seal.

The '624 iron heads were leftovers from the 2-piece days, but not the blocks.

 

2 piece rear main seal engines have the engine oil dip stick on the passenger side 1 piece have it on the driver side.

 

That is NOT SO!!!!!!

 

I have a early 86 coupe. The original engine had a one piece rear main cast iron heads. The dip stick is on the driver side. Look at any 85 with the original engine and the dip stick will be on the passenger side. The 86 engines at least in the corvettes were a one off year. Also they were flat tappet blocks.

 

Is there any special tool you need to install the seal like on the ls blocks?

 

My 86E had it on the passenger side, 1 piece rear main seal, which I had to have replaced from leaking eventually.

 

I don't believe you can find an OE/GM build of any C4 with a 'driver side' dip stick for engine!!!!

 

L83 and 85 L98 have the dipstick tube on the passenger side as was stated before. If your L98 or L83 C4 has a driver side dipstick, its been swapped, as has my L83 . Which is now a fusion of an L82 with a crossfire intake.

I can confirm also from my iron head 86, that the rms is one piece.

If you have a manual, i would refrain from replacing anything other than a friction disc.

I am 2 for 2 on imbalanced aftermarket clutch assemblies on 4+3’s. Its possible that its me, but i doubt it. So if u have a manual, and you are tempted to “do the clutch while you are in there” i would simply replace the friction disc. Nothing else.

 

He has an automatic.

https://www.corvetteforum.com/forums...rmance/4854784-86-automatic-transmission-replacement.html

 

Do you have to take the oil pan off for the one piece rear main seals? I want to make sure I have all the parts I need

 

Yes and or No. Depends.

You can not remove the aluminum 'housing' that the seal is pushed into unless the pan is removed. So if you leave the pan installed, you have to install the seal with the crank sticking through it, and the housing rigidly fixed. If you've never done a 1-piece rear main seal on anything this way, it is sort of easy to mess up the new seal upon installation. There are two special tools to facilitate a 'no damage' installation, but almost no one has or uses them. You have to be careful that you don't 'tear' the seal lip on the end of the crank as you push it onto the crank and into the housing, which occurs almost simultaneously. Sort of fussy. Particularly for a first-timer.

When I replace the seal during an engine overhaul, I use my bench vice to 'press' the new seal into the housing. I don't use a hammer. When installing the housing with seal already installed, it is possible to wiggle the seal over the crank, push the housing onto its dowels, and install the bolts. Not fussy at all, almost no opportunity to damage the seal lip.

If you have any signs of leaks at the oil pan gasket, I encourage you to replace the pan gasket at the same time and do the rear main seal as per the second paragraph.

No one has asked this question, so I will: If you're chasing an oil leak, what has led to the conclusion that it is the "rear main seal"? Many items can leak and look like its coming from the main seal. Valve covers, oil filter/oil cooler, oil pan gasket (corners), oil pressure switch(s), China wall on the intake manifold. The 1-piece rear main seals almost never leak. Vikingtrad3r had an episode with rear seals, he's been in this thread, perhaps he'll elaborate. It had to do with the type of material and the manufacturer of the new seal. He had to do the job over. I don't recall the details.

 

Thanks! This is a good answer I was looking for.
I have done many rear main seals before just not with these engines. I don’t believe I actually have a leak from the seal, I am replacing the transmission and know it is a good time to do that as well. That being said, I would still rather take the aluminum housing off with the seal and replace the gaskets behind that at the same time. I will probably buy the oil pan gasket and see how I'm doing on time when I get there as I will be using somebody else’s garage and trying to get it done in a day.