Resurrecting this older thread as I'm now starting the top end porting work. Port matching the plenum and injector housings has been straight forward on three sets that I now have. While I haven't put a burr in the castings yet, I'm happy with the relative alignment between the plenum and the injector housing runners.
I can't say the same about the primary runners between the injector housings and the heads. They are considerably off centerline. With no porting, there is a shift between the two resulting in a sharp step, which would really hammer the flow pattern. The offset isn't there with the secondaries, only the primaries. Placing the gasket on the head, then comparing it to the injector housing quickly shows the very poor port matching..
If my '91 is anywhere close to a representative example, I understand why the LT-5 responds so we'll to top end porting..
I'll try to get a couple of pics tomorrow morning to post for illustration.
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