How does grinding out the divider between the ports on the TPI intake help with airflow and RPM. Its a trick done on LT5s and helps a ton but Ive never seen any results on a TPI intake. That combined with SLP runners also ported to match could help. Anyone with info and pictures please help.

 

Here's a link to Mike Davis' site where he dynoed and track tested a siamesed base.

http://www.eecis.udel.edu/~davis/z28...age010511.html

He later hurt the engine with the intake, but it was not definitive whether or not the intake was the cause. I knew a couple people back in the late 80s that siamesed their base intakes - both slowed down, much like Mike's example and one hurt his engine,, same cylinder as Mike.

As seen in the dyno and subsequent track results, when you do this, it rolls off more power in the lower RPM than can be made up for on the top end,, especially for lower stall speed automatic cars. It might be an OK stop gap for a 383 or larger engine or a 350 with steep gears and manual transmission, assuming you're able to tune yourself,,, but I wouldn't run one - ever. You just end up with the worst and most inefficient single plane on the planet.

 

I've heard the same thing. I don't have any links of the top of my head, but everytime it comes up, there's never any real info showing benefits, and you always get the stories about how circumstantial evidence suggests it can be problematic.

....and if I'm not mistaken, keeping in mind that it's past 1am, I believe the LT5 lower manifold has more runner distance before the chambers, correct? Kinda Superram-ish? Whereas the TPI runners actually bolt up MUCH closer to the chambers? Wasn't the issue with the TPIs some sort of air/fuel/cylinder distribution issue?

 

You can't compare the Lt5 split runners because they siamese too the same cylinder. A pair of runners goes too the four valve heads, two intake valves per cylinder. The Lt5 mod turns 16 runners into 8.

Most people siamese a tpi too almost the same runner length as a superram runner. Turning their intake into a ghetto supperram, shorter runners and a larger plenum. Any more and you might as well switch to a short runner intake like a miniram or a stealthram.

 

I am running a fully siamesed TPI setup. All it does it create more of a volume for the combustion chambers to draw from in turn raising your RPM potential, nothing is lost down low when you tune for it, it still takes its' air in though from the same size throttle body, so remember that before people who haven't siamesed their own setups tell you that it is detrimental. You need to tune for your lower end to help O2 correction, meaning your VE and AE, as well as your SA. You also need to run a higher stall speed to see/feel any real benefit while driving. Pics of my system that I ported are on the first page of my build but I will post some here because you requested pics, and I also threw in the latest video I posted which embellishes the intercooler location, but I throw a few revs of the siamesed 305 if you want to hear it run with no hiccups. EBL-P4 runs the show. Audio on the camera isn't too great, and it is running an open downpipe...

 

Ho lee chit, mahn! Great looking engine

Did you check out the sticky on "Quest for a better flowing tpi"?

 

I will post up my results from a test drive when I'm finished. I did get a new aftermarket tpi intake and ported my plenum ans slp runners. I still have the stock heads and cam so this will be a true test from down low takeoff to high rpm highway driving, I will get back to you on my test.

 

I will post up my results from a test drive when I'm finished. I did get a new aftermarket tpi intake and ported my plenum ans slp runners. I still have the stock heads and cam so this will be a true test from down low takeoff to high rpm highway driving, I will get back to you on my test.