OK, I have read the "Siamese TPI intake base - question" and I have thought of a few ideas from that article. My question is this: I decided to leave the bottom four inches of the runner/divider wall in the base(siamesed the top 2 inches) port matched to the cylinder heads. I have a two pairs of SLP runners(unported and fully ported) and a Plenum (only ported behind the throttle body). I read all of the information posted on runners and "ram" efects and pressure. What I was thinking was if I were to siamese the Plenum to the SLPs and vice versa and only siamesed the SLPs in about one inch with port matching and a smooth transition. Then siamese the SLPs at the bottom inch to two inches max. That seems like I would have a fair amount of runner length left for the "ram" effect and to keep pressure there to keep air moving when the valve is closed. I do not know if this would make the runners a potential "Plenum" or it would make virtually the whole system a "Plenum."
I had thought about only leaving the bottom 4 inches of runner/divider in the base and then just port and siamese everything else up. I did not know if Ed Maher or MadMax or swapmaster had done this yet. I thought that Jake Jr was going to try this idea from one post but I was not sure. Any opinions.

 

I wouldn't siamese the base in at all* - rather I would just enlarge the openings as much as possible. As far as the SLP runners, if you only siamese in one or two inches on top & bottom, they'll retain a long actual runner length for velocity and yet they will flow signifcantly better up top. It isn't rocket science so don't hurt your head with detailed specifics. Basically, the further you siamese into the runner, the shorter you are making the actual length - not so much a plenum extension, just a runner that "acts like" it is shorter.

*there is a risk of unequal air charge from non-precise work. Even if it looks totally fine to the eye, things are quite different when the engine is breathing in thousands of times a minute. You can bring a very early death to the engine by starving a cylinder - scary. Just not worth taking the risk for a few extra horsies.

 

People have been siamesing for a while and the people who have not gone extreme in the siamese have seen good results. Raising the powerband and improving horse power and torque. Which is what my engine will need when the rebuild is done, a slightly higher band.

I am pretty much dead set on samesing the first 1/2 inch to 1 inch of the SLP runner to the plenum. I was thinking that the siamesed base would act as a H-pipe in the TPI.

The other way I thought of doing it that have have pretty much decided against was to port everything from th base up. I decided not to do this because I was worried how it would affect vaccum accesories such as my MAP sensor, FPR, etc.,. This also would have only given me four inches of runner total in the whole system. Basically making it (runners) into the plenum because it would out flow my heads. I would also think that from the information from the thread that I would lose almost all of my "ram effect" moving the power curve higher in the RPMs to pull the same/more power.

My other option that I had thought about seems to make the most sense to me. Leave the base stock, unsiamesed but ported, and siamese the top have of the runner to the plenum. This set-up would seem like it would be able to pull in more air but still have a bit of "ram effect" to keep the air moving when the valve is closed.

Which one of these set-ups sounds the best, or what did I get wrong?