So after a full rebuild, and 250 miles of driving so far, I noticed an oil leak. Sure enough its the rear of the intake manifold. My question is, with so few miles on the engine are the cork gaskets reusable?

 

What cork gaskets???

 

On the late model LT1's there are no cork gaskets. It's just sealant between the block and intake manifold surface and since it's such a large gap it can be a tall order to keep oil where it belongs.
This is a very common problem with all late LT1's. Do a search and you'll find all kinds of info. IMO if you run into something that tells you to either scuff or dimple the block/intake surface it really isn't necessary. Just taking your time, making sure all mating surfaces are spotlessly clean, making sure to install the intake striaght down onto the block, waiting several hours for sealant to cure and retorquing the bolts after a weeks worth of driving is a good combination. Quality sealants to use are either Ultra black/copper or GM sealant.

 

You need to have your manifold installed by someone who know's what they're doing.

 

Ok...

So originally when the engine went caput, I was told there would be a dissassembly fee by one particular engine shop. The price was good otherwise so i went that route. When I was ready to take it, the shop owner had a personal issue so I found another builder who...charged no fee for disassembly. Too late.

Well, when I pulled the manifold off, obviously the sealant is there, but there were also 2 cork looking gaskets that went between the head and intake ports. Note: I have the paper history for the car and about a year before I bought the car, there was a shop repair fixing the same problem i have now. I assumed that the same type of gaskets were used during the most recent rebuild which is what led me to ask my question.

edit: found one of the old ones, not cork but it's a very brittle material different than conventional gasket material. Also found out it's a good idea to put a thin layer of sealant on the gasket itself during reassembly, I'll be ordering some fel-pros shortly. Thanks for the input guys.