I have a 1990 Chevy g20 with a 5.7l v8 -
I changed the oil pan gasket quite a few years ago and at that time i almost did the rear main seal but life had other plans and I had to button it back up in record time so it didn't get done then.
Now The engine is leaking all around again and I will be doing the oil pan gasket amongst a bunch of other things.

For the life of me i can't track down that seal! I remember it being a half circle that you have to snake into the engine block and around the crank shaft. (i'm looking at the directions and pictures in Haynes Manual so i know i'm not crazy)

I have searched in every way i know how and keep coming up empty handed. will also be checking the timing chain variances so will be doing all those gaskets as well. Not sure if the front seal will be part of a timing chain seal kit but I haven't found anything in a half round shape. Everything that comes up under my searches is a complete circle seal. Are these meant to be cut to size? I swear the part i bought all those years ago was a half circle seal.. . really confused so if anyone would be willing to illuminate me I'd be grateful to say the least.

 

when I google it a bunch of seals come up that look right but all the sites say it's incompatible with my van . this is the type of thing that's coming up as a fit...

 

The 2 piece rear main seals were phased out in the mid to late 80’s - by 1990 there was a cover plate was added to allow for a 1 piece seal that didn’t require removing the rear main cap to replace.

If your engine has a 2 piece seal, the engine may have been replaced with an earlier block. Check the casting number and Google it to decode and verify.


Number on the right is the casting number.

 

Ah, okay thanks for the response - this is interesting.
I do know the block was replaced before i bought it almost 10 years ago. this would probably solve a few mysteries. once I can get the number how do I look it up to get the specifics? thanks

 

Here’s a good website I found - lots of good info - the casting numbers & decode start after the first few paragraphs.

https://www.chevyhardcore.com/news/r...sting-numbers/

 

this is great thanks. getting that code will have to wait until i get in there and remove the alternator i think. seems like it's buried behind the bracket. will be a few weeks before I can start. will report back once I get to it. thanks again

 

Actually it looks like you need to take the engine cover off inside the cab to see it from that pic.

 

ha! yeah been a long day. totally right. will check in the am

 

Both answers may be correct.

The casting numbers are sometimes on both ends of the block, so there could be one on the front end as well. I can’t recall exactly which engines do have it on opposing corners - and truth be known, I could be confusing it with Ford or Dodge - so no guarantees.

Either way, I’d still prefer pulling the dog house over the alternator.

 

Due to more gasket issues all around I've decided to pull the engine out and go over the whole thing so I don't have to worry about installing the RMS while the trans is attached.