Well since my MK-I engine is about ready to get fired, naturally I want to start looking towards a MK-II design. That being said MK-II is going to be about more power and seeing about working around the limitations of the stock TPI. I was wondering if any one had ported their TPI intake in the way described and if they had results from it. What I'm wanting to do is take a stock TPI base, cut holes where the red is (see attachment) and then make it so that the floor is "flat." in this area. Overall I would like to reduce the length of the runners here from 6" stock to 3-3.5". The idea is to create a series of 4 small "plenums" in the base. After that plates would be welded or epoxied back on to cover up the holes. Thoughts?

 

This is what most do

https://www.thirdgen.org/siameseport

 

Yes, but I'm not sure cutting and welding in plates in that area is really going to make much difference over just cutting inside the intake itself there. The port at the head is very small and needs to be made as large as possible.

 

The design of the TPI just does not complement high RPM usage very well, regardless of how much you modify or siamese the base. The base was designed to get long runners under the hood and has a funky entrance angle. The curved runners impedes flow and heats the air while being pulled against the sides,,, and the travel (heat up) time is the same from t/b to valve whether siamesed or not. Basically,, after siamesing the base,,, you'll end up with the worst flowing and least efficient short runner intake on the planet.

The tuned effect the extra runner length gives is about all the GM based TPI has going for it and to an extent allows it to over come the basic design inefficiencies. There is definitely a point of diminishing return as far as how much you can siamese,, and usually that’s somewhere within the RUNNERS,, not the base. Meaning at some point you'll take away more midrange power than you can make up for on the high end - regardless of the combination.

 

If you want to port your TPI base, you should start here for info:

https://www.thirdgen.org/forums/tpi/...owing-tpi.html

 

Anyone have real numbers from a siamesed based?

 

Mk I and Mk II what are you referring to?

Personally I wouldnt do it, just put a good short runner intake on there if thats what youre after. Its like making a fat woman dance on stage, she can do it but it just dont seem right.

Havent done it myself but unless youre throwing cubes at it most have reported noticeable torque/ET losses that werent worth the gain meaning raising the rpm ceiling. So it revs higher big deal doesnt mean its faster overall.
Theres always the exception to the rule but imagine someone with a miniram trying to weld metal on to extend the runner length trying to build low rpm torque and not lose hp kind of rediculous no?

 

Yes, after thinking it does seem kinda off a backward way to go. Like taking a short tube setup and putting on a bad flowing intake on top of it. I'm still undecided, but thinking a lot. I HATE that I want to stay TPI so bad(for the look and originiality. My combo is a 355 with AFRs and a BIG Vortech ysi supercharger. Search my name for the build thread...

 

ahahaha