Siamesing Your TPI Intake

I really didnt like how every race I was in I jumped out front of right away spinning and didnt have much of anything left after 4000rpm so here’s what I did and here’s the results.

I have been looking into either miniram or superram but heres a SUPER way to get right in the middle.

Before starting I made sure to have eye protection, a cheap yet effective breathing mask, and long sleeve t-shirt. I removed all of items before going back into the house because just to have one metal sliver from my eye cost me $475.00! I also put on a set of headphones and had a fan blowing the metal away from me, and cooling because it gets hot in a long sleeve shirt this time of year.

By siamesing the runners I made more area for air to be freely grabbed by the engine

I smoothed out the plenum also to fit perfectly with the new larger runners. I didnt just take out the center. I left some of it in the center so help smooth the air before it entered the siamesed intake.

Doing the runners took a total of 5-6 hours after smoothing and polishing was finally finished.

The intake was done by me also, it was very time consuming (4 hours).

Gasket matching was very important to me and to be exact here’s what I did:

  1. Order aset of BIG MOUTH MANIFOLD gaskets from TPIS ($18.00) and cut them with a brand new SHARP razor into a siamesed shape.
  2. After You have cut the gaskets and left enough room on all corners for a proper seal take the gaskets and set them on the runners with a little bit of silicone. Line them up with the bolt holes perfectly.
  3. Get some flat highly visible spray paint. Using gloss seems to stick to the gaskets and doesnt alow the gaskets to make a proper seal once installed. Spray the inside edges of the runners, plenum,and intake. Now you have the perect outline for porting these to match perfectly.
  4. Get some gear oil (not motor oil) and dip your carbide tip in the oil every 3-4 minutes allowing the bit to be lubricated while cutting helps heat dissipation and extends the sharpness of the blades while helping you get done faster. Gear oil seems to work better than motor oil. I dont know why but it does.

I was having serious traction problems that could have eventually had a toll on my drivetrain and expensive rear tires.

I took it out for a spin and a few races and heres what I noticed.

Before: The 383 and TPI are both TORQUE monsters, so from a launch I was spinning sometimes until shifting into 3rd. After hookup I didnt have much less after 4-4500rpm do to tuned port injections limits in higher rpm’s.

After: From a launch I still burn the tires, but only for about 5-8 feet. Through first my car doesnt seem to have the same insane pull, but after it hooks and shifts into 2nd gear the car jumps into hyper mode and definatly hits a hot spot all the way up to 6000rpm’s and feels great doing it.

Tools needed:

  1. Carbide cutting tips. I would recommend 2-3 these can be found on ebay fairly cheap. You can also find them in Post Tools.
  2. Air Compressor with a cutting tool with at least 33,000,00rpm capability. Dremel will work but will take much longer.
  3. Cutting oil for the tips. I used Gear oil.
  4. Spray paint NON-gloss
  5. Some type of measuring tool for matching. I used a micrometer.

Dont bother using the grinding stones on aluminum. They just get caked with aluminum and fail to work properly.

This mod will succesfully help you gain upper rpm’s. I would only recommend this modification to a aftermarket manifold if you are confident in your porting skills. If you have a stock manifold I highly recommend this modification. I have read posts on the TPI board over at where madmax (who was the first person to post this modification on a stock manifold. There is also actual DYNO results proving this modifications validity) siameses a stock manifold and yielded more rpm’s a smoother powerband and increasing TQ in higher rpm’s.

Important note: On the SLP Siamesed runners I noticed there are sections that are thinner for proper bolt clearance. Be VERY careful not to port through the runners. If you do, take it to a muffler shop and have them weld it. You are going to have to grind it down and fix it. Be smart patient and save alot of time.