I'm trying to get as much HP for my dollar as possible. How much hp does an aftermarket base with aftermarket runners have over a ported-as-much-as-possible-and-siamesed-1-inch stock base and aftermarket runners? 5hp?

Is it worth it that much to go with an aftermarket base?

I have an Lb9 car and I'm debating between modded TPI or LT1. I love the way Tpi looks and I know it's limits and all, but I also know car lovers can exaggerate quite a bit. For instance, when I was with the GTP community they would say a certain header would yeild much better gains over another header, eventhough dyno was w/i 1-2 hp of eachother and 1/4 times were the same.

Please give me a non-biased opinion and if you've dealt with both TPI, modded TPi, and Lt1 that would really help.

 

If you're talking about an engine with the potential to make less than 400 horses (at the crank) there will be liittle difference in ET from a fully ported (NOT siamesed) stock base and a mild clean up on an aftermarket base. However, you'll need a 6" burr and a dremel with a wand attachement to be able to port the intake from entry to exit.

In your case, if we're talking basically stock 305 with stock heads, all I'd do would be remove the lip / radius at the entry area and smooth the casting out (end to end). I would not siamese the base at all. You'll trade off more midrange than you'll make up on the upper end,,, especially with a basically stock engine with highway gearing and a stock torque converter. I started slowing down after siamesing SLP runners to about the halfway point on a 400 - 415 horse 355 with 3.23 gears and a 2800 -3000 rpm stall. So, in my opinion,,, bang for the buck in your case would be ported base and cleaned up SLP runners.