hrspwr

iTrader: (3)

For a while now I have been looking at different threads in regards to Siamesing TPI intakes. There are basically two ways that everyone says works. The first is doing the runners about 3/4 of the way down, where others leave the runners alone and do the base. Both shorten the runner length but one more than the other. Correct me if I am wrong, but when you siamese the base about 2-3" in, the intake valve in now drawing air from two runners instead of one. Is there not more turbulence in the air at the point where it has been siamesed compared to if you siamese the runners only?
I want to see if anyone has done one and/or the other in a compare to see which is better. I am in the process of siamesing a pair of stock runners just to see what it will do as i have an extra TPI intake to play with. I am looking for any input and experience you have.

cuisinartvette

There are some out there, if they could would siamese everything down to THIS!



Dont siamese the base where it goes into the head all youre doing is slowing down and skewing your intake charge

If you do anything just go in the top of the runner some. Port the rest of the runner and base best you can and you got what you got.

If you want more get a shorter runner intake system.

A fat chick can work at a strip club but that dont mean she looks good doin it

hrspwr

iTrader: (3)

Basically what I am going to do is siamese the runners the same way that ASM did theirs, except a bit more.
But the thing that still has me wondering is siamesing the base, and not the runners at all. Want to know how much a difference there would be between the two types (siamese base with untouched runners vs. siamese runners untouched base).

ASE doc

It seems to me from my knowledge of fluid dynamics that siamezing the base and leaving the runners alone would create a void where the velocity produced in the runners would be lost. This would basically kill the ram effect that TPI is all about. If you look at proven successes in siamezing TPI, they all involve siamezing from the plenum down as far as 2-3" from the heads in some cases. If you are using extruded tube runners, you will be limited to the upper 3/4 of the runners because you need to retain access to the mounting bolts. This prevents you from siamezing the entire runner set. The most extreme of the those siamesed TPIs that have shown success used SLP runners because they lend themselves more to siamezing. To make this work you need to cut open the runners. Then you can open the up and weld them back together.

The most extreme and successful siamesed TPI I have seen was done by Alan in California(89GTATransAm) and Dyno Don. It made 420whp on the dyno. You can PM them for details on how they made it work.

I would have to say the photo cuisinartvette posted above is a great example of how to ruin a small block chevy head.

hrspwr

iTrader: (3)

The picture just appeared, as the last time it was not there. That is a great way to ruin a sbc head....
I agree in the fact that opening the base and leaving the runners untouched would slow the velocity of the air going through the port. I would assume it reduces peak tq, but would it make a broader power curve and not fall like the TPI is known for?

ASE doc

With the right heads, cam, and hi flow parts ported for maximum flow, you can go a long way towards curing the low rev ceiling of TPI. A large cam like the ZZX that I run(240/240 @.050 .560/.560 112LSA), along with hi flowing heads and intake and large primary headers will reduce peak torque but at the same time broaden the power significantly so that overall power is vastly increased. To take this even further, add siamesed large tube runners or siamesed and ported SLP runners.

I beleive that siamesing the base and leaving the runners stock will probably not spread the power band enough to compensate for the loss of peak torque.

There are many differing opinions on these things. I really don't have any experience with siamesed systems as I have not siamesed any of the TPIs I've built. I can only draw on my knowledge of fluid dynamics which is sketchy. I know only what I've done and my own results.

As for your own ideas, factory TPI bases are a dime a dozen. Buy a couple and play with them. You can try whatever you like and find out for yourself. Let us know how it works.