I am about to start my rebuild. I will be using my already assembled longblock from my other car. It is a 355, forged flattop's, good rods w/ ARP bolts, steel crank, and Dart sportsman 200cc heads with the chambers and bowls done, and the exhaust mildly ported. All head work was done by Summit Racing about 10 years ago when they started selling modified parts. I will probably be using a Comp hyd roller, the 305 on a 114 center.

The real part of my question is what to do with my TPI. I have a procharger 10 psi twin intercooled setup on the car already, so the TPI becomes less of a restriction since it's pressurized. I am determined to use the TPI, and a modified stock one would be really cool

Can anyone (who has done it) tell me to what length they have siamesed which parts and how much improvement whas made? I have read at ThirdGen.org about siamesing runners, siamesing plenum's(where the runners attach), and siamesing bases. One guy siamesed almost his whole base- but I am looking for some solid results.

I am a fabricator and am really up to the challenge. I understand the TPI's shortcomings and I am willing to trade some of that low end for better top end flow. The SC added so much low end I dont think it wil be missed anyway.

I was thinking about porting the stock base, possibly siamesing a porting of it, and fully siamesing the runners. For the plenum I was thinking about adding volume by increasing its height- or even better- its width. Which would require shortening the runner length and further increase flow.

Anyone who has modded their stock TPI please reply with your results.

 

You can check out results of a 1"x1" stock base port job on my site; the main result was a gain of 20chp at about 5,200rpm. I've seen those deep siamese jobs of that forum.

I cannot speculate about how it would work with a blower, but you might pick up a used stock base and give it a try. I bought a used set of base & runners for $100 for my experiment with siamese base & lower runners (I just cut about 1/4" up into the lower runner flange).

I don't think that a siamese base along with siamese runners would work well, but you could of course try that too.

 

From things that I've read, you'll need to do whatever your can to increase the diameter (volume) of the base and runners. The problem is that there is not much material to do so.

If you are a fabricator then just "weld in" larger diameter tubes for the runners...or just go hog wild and take some "j" piping and "weld" that to the base. Or just make your own super ram by cutting half of the tubes down and putting a big box on top of it.

Alas...or just do what we all do and buy an intake that is already done. You might want to look into the "first" brand full runner tpi system. :lurk:

 

Yeah I saw the FIRST system. Its seems ok but runner length is still a little long looking. I am thinking about siamesing the runners completely, siamesing the base some at the entry where the runner meets it, and maybe widening the plenum/shortening the runnersimiliar to the way a superram is but not to that extent. I have three TPI setups to play with, so I can try a few things.