I noticed in some pics that Gulstrand used to almost siamese the TPI runners. It probally would'nt be to hard to cut and weld them.I thought this would be a cheap way to shorten the runner length to have a little more high end power. This is not the greatest pic but you can see they are joined together in the middle. I wonder if you could do this with JB weld ? http://www.vetteweb.com/features/vem...ldstrand_gs80/

 

Ive wondered about them myself in the past before...I even have the Vette maagzine from the 80s when this car was featured in it.
The rpm claim is 5500 rpms with their engines.Keep in mind its heavily modified for its time.I love this car,and it was a great set up throughout.

I do not know if doing this will raise the rpm wall that high...

I believe TPIS did this siamese mod to their large tube runners but stopped because of problems with the welds holding/cracking over time.The stock and large runners have very thin tubes and because they are curved,I really doubt JB weld or some type of epoxy would hold that long over time.

I had a few spare TPI runners before..a stock set I cut one side open to see if it could be done.Youd have to weld a plate to the inside of the runner tubes before cutting the outside because its very weak.

Then you can do the mod from there and weld the back or outside plate onto the runners to close it up.

Theres very little room for error since theyre so thin walled..these days you can find super cheap runners for sale to mod if you want to try it..however,youre better off finding someone to weld them correctly and not use JB on it if you cant weld aluminum at home.

Im very curious to see if it is possible to raise the rpm peak of the TPI by shortening the runners down inside..one other thing,I dont know if there can be reversion with this mod.Its TPI but its not,and dont know if the flow/is it harmonics? can go backwards or whatnot.

 

Why not just cut a 1"high x 1-2"deep hole in the intake base runners.

This mod effectively doubles the runner diameter yet retains the runner length. The effect is to make a compound oscillator of the air column so still have some of the stock ram air effect at low RPM yet breaths well up top too.

My L98 now pulls well to the 5,800rpm WOT shift points; before & after dyno pulls on my site (click on the label below the Vette pic).

I would also recommend porting the base, though I have not yet done this as I do not have a die grinder and a Dremel is just too damn slow.

 

If those cars are breathing at 5500 rpm than our cars should do the same since they would have the same intake on them. The JB weld was sort of a joke but I did not realize it would be so difficult to do this mod. It would be better to bring to a welder.