There's a big hidden lesson in that thread. For those who haven't taken the time, PatG did that with a fast 90 intake, AFR 205 heads, and a 23x/24x cam, and - dare I say it - YT rockers. Think of how much "better" hardware we have now vs 2007 when PatG wrote that thread.

He chose AFR 205 over the AFR 225 - smaller port, better airspeed. Airspeed > flow numbers for making power. He even mentioned it in one of this posts. Ever stop and think about this: Why do so many end up in the 450-480 hp range with bigger heads, bigger cams, fast 102 intakes, etc, etc, etc? Talk to any of the big boys out there, and they'll tell you the top three concerns for designing heads are airspeed, airspeed, and airspeed. All too often I see people go for the biggest port they can find so they can make the big power numbers and fall short. I'm to the point that I recommend spending the money on a 5 angle valve job before porting the factory heads - especially the LS3 heads.

There's a part of me that wishes I had more time for this type of build, but I'd love to put together a LQ9 bottom end with AFR 205's and a single pattern 220/220-110+4 cam for an absolute torque-monster of a truck engine.

 

David Vizard has some good power videos on youtube. One thing I picked up on was that airspeed on a cathedal port is on the top side of the runner. The lower side has slower airspeed. Hogging out the runner is detrimental. He showed how raising the intake port floor increased velocity.

 

I think i read that somewhere too.

 

that's kind of why I was under the assumption that the 102 intake was killing low end torque... And waiting for the 215 trick flow heads versus the two 220s.. Velocity / Air Speed

 

I did email him yesterday.

 

I think the same is true for the LS3 ports. If you fill in the bottom and soften that short side radius, I think the port velocity - and consequently the power - will increase, even though the port is smaller.

 

The 102 makes for very strong midrange torque. As to the port size, what I try to look at is the flow vs the port size. the heads on my 346 were 220's, but they flowed 330 cfm. Now, if you take a 205cc head and spot it 300 cfm. Then look at a 215cc head that also flows 300 cfm, you can take to the bank the 205 head will outrun the 215 head. Unfortunately, it isn't as simple as "go bigger / go smaller". Sometimes you have a perfect port size, but the valve size is too big, and the cylinder wall shrouds it. Other times, the valve is too small, and it kills low lift flow numbers.

I find the fast 102 is a better intake vs the fast 90. I wasn't trying to trash it at all. I was more stating what PatG did was all the more impressive, given that he did NOT have the fast 102 available. I did a comparison thread with a ported fast 102 vs the msd on my motor, and you can see the midrange ont he 102 is really strong. I'll try to find that thread. It was in the external gen 3 section....

https://ls1tech.com/forums/generatio...o-fast102.html

There it is. Post 9 has the curve overlays

 

The Fast 102 has about 1 to 1.5 inch shorter runners vs the Fast 92. That might make for faster airflow since it's less distance traveled. I'd assume the plenum is slightly larger as well.

 

Those shorter runners will also weaken low end power compared to if longer ones were available.