Willwren was giving me some examples of the differnent parts on heads, and that they're different for a reason, and the port mismatch is one of those things i've kinda heard in a few places.

but i'll compare my pix of the L27 LIM i gave to Damemorder, and compare to the L67 one underneath my bed after class

What I recall telling you was that nobody KNEW if the heads were different, and that there was a possibility in porting difference. What I meant by that was COOLANT passages.

DrJay and I are comparing online pics right now. The block face of the heads looks the same so far. Some cast numbers match, some don't. So far.

I removed my exhaust headers ( manifolds ?) and ported them. I can tell you
they were not that bad from the factory. Infact they looked better than many aftermarket ones I have come across. They appeared to be CNC machined or something similar.
The gasket was MAYBE 1/32 off at the edges. I guess my point is I'm not sure it was worth all the effort. GM did a good job here. A high flow muffler may be a better choice and easier. They are a witch to take off and line back up. I recommend elongating the bolt holes just a bit. I've saw many post on the GP boards where guys are running high 12'* with stock headers.

JLathem

just to clarify, those are manifolds, not headers

Tubular manifolds. And that'* not surfer-talk. I gave that up years ago.

Well, I always thought that headers were pipes welded to a flange. My SSEI has pipes welded to a flange. Now they may not go all the way back in equal lenght to a collector like the SLP headers but, they are pipes not cast. They do have a flange that is CNC'd. I'm not saying they are " headers " like hooker'* or whatever, but they are not cast iron manifolds.
Hence my flip flopping on the term.


JLathem

Well i'm talking about the valvetrain.

Our exhaust manifolds are basically port matched from the factory.

I remember a guy who converted to L67 talking about the ports being different... Maybe it was just the Lower manifold?

Hell, I don't know. DrJay and I can't finish any conclusions right now on the heads either. We need pics of the intake side. I know exhaust is the same, and the block face LOOKS the same, but we see different and same casting numbers in different places.

We may need to start another fresh topic for the sole purpose of comparing the L27 to the Series 1 L67. Really nail down the unknowns.

http://www.bonnevilleclub.com/forum/...c.php?p=261296

For further discussion. Reference this topic, cut/paste if you choose, but back up your findings and conclusions with fact and alot of pics.