LS6 PCV and steam tubes:
There really are some differences in the ls1's between all the years of LS1s. As mentioned earlier I swapped heads from a 98 to late model. Man did this ever burn me.
-98 coils bolt directly to valve covers not to a bracket then to the covers like the rest of the years (I knew this)
-98 valve covers have a different bolt pattern (around the perimeter rather than the normal 4 bolt up the center style <- I didn't know this)
-oil filler cap on the 98 valve covers doesn?t use the riser tube (GM #1255-9505). You?ll need this or the cap will interfere with the front-most coil
-98 coils can be used with 99 brackets but one coil on each bank has to be flipped over to mount properly
-there are TWO types of coils that came on the 99-02 ls1. Brackets DO NOT mix and match (guess who got the wrong ones.)
The other detail about heads was that the valve covers I ended up with only had one port on the passenger side. This meant that the 98 ls1 pcv system wasn't going to work. I had ordered the breather kit from Speed Inc before doing much research since I was pushing hard to get this done. The idea is that you put a breather in each head, or even just one head if you trust bay to bay transfer. The problem is that while you do relieve the pressure you don't clear out any blowby gases and the life of your oil goes to crap because of the junk getting in it.
So I caved and bought the ls6 valley cover. Yanked the intake manifold off one more time.
Here's the difference in valley covers:
By sucking vapor from the valley you get a lot less oil consumption, plus as mentioned, the PCV still works properly and that was the only way it was going to happen with my valve covers. There's a good write-up on how to do the swap and the parts needed on ls1howto.com.
The only piece they don't talk about much is the crossover tubes (AKA the steam tubes from my inquiry earlier in the thread.) In order for the stock ls1 tubes to be used I had already done quite a bit of rib carving on the bottom side of my ls6 intake. However the PCV pulls from the a line which conflicts with the stock tubes such that I decided not to keep bending and prying.
Instead I just did it right and used the ls6 tubes (which is really a single side to side up front and plugs for the back) I got a while back. I thought the ls1 would be better but as the engine does tip up somewhat those back vents probably won't do much for letting coolant bubble out anyways.
[Ed note: if you?re feeling hardcore you can get adaptors for these fittings into AN lines. That lets you run all 4. See 65imp?s ?TVR? build for details.]