Making short 102 runners
 

I am tired of waiting on fast so decided to experiment my self since I could not find anybody on web that has tried this and documented it should be going to dyno in a month previous setup made 605 lumberjack cam IPS stage 2 heads catted kooks and VR intake fast manifold 12.0 comp changes this winter 102 TB full 4" intake electric water pump and I took my cats out and these shortened runners my car has a cam that when designed on engine dyno with single plan made power to 7600 but peaks at 6400 with the fast so hoping these can move that up to about 6800-7k
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i got some more work to do on shaping and smoothing the bellmouth for entry but i wana know what all the pros on here think and how pronounced does the bell need to be the stock castings are not very good in opinion really only the bottom has a good lip

Looks good man. Interested to see your results. How many inches to you take off the runners?

BTW, I doubt you'll find any induction experts on this page lol.

Good luck with the project though!

i am hoping somebody will put me in touch with anybody that knows anything about this stuff runners are all 8inches long so i took off 4 inch on the long side basicially just the turn down i was going to go with a 5" length just figured that might be to short

In for results. I've wanted to do this same thing to mine over the last couple months.

Runner Length
 

So they were 12 inches now they are about 8 inches?

air is funny stuff. as you are doing this (and I suspect you want to do whatever it takes to provide volume and charge speed), keep in mind that the air going through the intake and all of its parts at times is traveling more than 100mph. So every little ridge/depression will have some affect.
It is too bad that no one makes a round bellmouth snap in for these runners. It would make a little difference to those wanting to squeak out a few more hp.
my experience has been that reducing the intake runner length the torque curve was more flatter while if the length was increased the torque output curve peaked more.
Tuned intake runners and air flow gets into a lot of math. Dont know if you want to get into all that?

Couple of comments..

The bell mouth / entry way is critical to flow, it makes a significant difference. I would try to reproduce the depth and outside radius of the bell as closely as possible.

If you really took a third of the runner length off, maybe you just trashed a set of runners.. That seems like a radical change to me.

Finally, what are you using to build up the entry with? How confident are you that the material will stay in place during the heat and vibration it will see in operation? What would happen if a chunk comes off and ingested?

Brave man, good luck. :cheers:

Did you check the legnths of the shortened FAST runners they came out with sometime last year? There were 2 shorter runners ( I heard they were a couple hundred dollars). If it doesn't work out, you could buy the shorter runners from FAST.

I have called fast every month for a year and various emails they are saposed to be releasing runners for the ls3 port only this month which I have been hearing for a year blah blah with no eta for ls7 ports very small market I guess

I ran into clearance issuies once I formed bell mouths so I had to cut them down to 6" and u found a heat gun set to 1200 deg shapes the raw cuts very nicely and when u look at te bell mouths they are a ****** design not much there really and from what I can tell by pics the high hp runners are about 7" and race runners about 4"

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This is what they are saposed to be coming out with
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Yeah, those red ones are SHORT, so I guess you are on-track. And from your post, sounds like you are just re-shaping the existing plastic with heat, so that is (probably) a pretty safe way to go.

Good luck, post a dyno run when complete if you can. :cheers:

i will deff post results win or fail hoping to be on dyno in a month month and half will depend on weather

and i should be able to lay it over my old graph and see exactly where gains or losses were made

You could use 3M panel bonding adhesive. It's very awesome stuff. Also there's a product head ports use called Splash Zone to fill and reshape intake ports.

Maybe this sounds like more than what you're wanting/willing to do, but if it was me, I'd be CNC machining the bell mouth out of a chunk of aluminum to ensure smoothness and consistency. If the interior matched the same as the interior of the plastic runners and the exterior was a wall thickness larger the joining end (opposite the bell) could be machined to match the plastic exterior and create a slip fit that could be glued in place. If the machining were really slick, it could incorporate a tab that allowed opposite bank runners to join with a simple connector held in place with a drive rivet or screw that would eliminate glue. You could make sets of different lengths and easily make changes from one length to another for testing by simply changing the length of the connector. There is no requirement to make parts from the same materials.

i am pretty sure with anuf heat and time i think i can up with a way to mold the ends to resemble very closely to that of a cr5 velocity stack we shall see today

Would be super simple to 3d print some ends.