I’m gonna be getting some headwork done next spring for my LS (which will have cams/gears/i/h/e at that time) and am thinking of either getting my IM match ported or spending a lot more extra cash on a skunk2 IM. I don’t really want any bottlenecks, but I don’t want to spend $250 on something I don’t really need.
Will the larger runners will help put more torque all across the powerband or more peak hp? Just curious if a Skunk2 IM is a good idea with a 4-1 or a 4-2-1. Thanks!
A skunk2 manifold is basically an ITR manifold that will bolt up to your head. Not an exact copy, but similar in style. It has shorter runners and a larger surge tank. Both of these will increase your top-end power although the manifolds are not known to decrease low- and mid-range power too much. I would go for it over a ported stock piece. Any cams you get will be biased towards high-rpm power so the skunk2 will get you the most power out of them. Of course, the skunk2 is known to have a good bit of casting flash left in it, so getting it extrude honed and port-matched would probably net you a few more horses. The best price I’ve seen on the skunk2 is $299 from nrg-racing.com.
I actually noticed an increase in low to mid with my skunk2 IM. It’s much more torquey at lower RPM’s. Everyone says there supposed to be highend power gains… I can definately tell the difference at lower RPM’s. I portmatched a 68mm TB myself with a dremel. It wasn’t hard just took a little time.
you care to share the “how to” on port matching the TB yourself? I’m sure many members here would love to know how to do that.
-Steve
DAY U IZ: Port matching and overboring a throttle body or anything for that matter are different. Port matching usually refers to the actually end of the ports being the same size to reduce the strong immediate turbulence air can experience when going from a pipe 64mm in diameter to 68mm. Overboring can not be done with a dremel as it requires the whole interior of the tb to be enlarged and a new butterfly valve to be fabricated.
How to Portmatch a larger TB to a smaller intake manifold. I have not ventured to port match in the opposite direction nor would I suggest it. skunk2 intake manifold is 64mm stock. most aftermarket TB’s come in 62 or 68mm. I bought a 68mm. I used my dremel, got the router attachment (router attachment really helps to make a strait cut) and a steel cutting bit. It, the steel cutting bit that is, looks kinda a small serated drum. Next I took the 68mm gasket that came with my tb. I lined up the bolt holes in the gasket to the bolt holes in my manifold. BTW the manifold is not on the car nor would I ever dream of porting it while the IM is still installed. Once the bolt holes and airpassage of the gasket are lined up with the manifold, I used a black el marko to mark the exposed manifold area. Essentially making a 4mm wide mark around the opening in the manifold to show how much I needed to cut. Next I started to cut on the high RPM settigng. The bit size I had only cut less than a fingertip deep so I used the adjustment on the router attachment to keep pushing the cutting bit deeper. Be careful to not cut too close to the air passages, 68mm in a perfect circle gets too close to one of the airpassage on the TB so I left a bit of a bump near the air passage. Remember I was using a b16a stylewith one air passage, the Type R and B17a have two smaller airpassages and I am unsure if they would get in the way of a 68mm TB. I took me three stages to cut as deep as the router attachment would allow. I then switched to a similar bit that looks like a dull pencil to clean up the rest of the inside of the IM. Wear a breathing mask and goggles aluminium filings and dust are not good for your eyes or lungs. Make sure you clean all the dust out of the inside of the IM. You might even want to stick something inside the chamber before you start. It took me forever to clean all the shavings out of my manifold.
If you elect to go with SI components like I did you will have to extend the wire for your map sensor, you can keep your same plug but will need the map sensor off a B series IM that has the map sensor located on the Throttlebody. The Skunk2 is a pretty good manifold, Endyn is using this manifold a lot and claim some awesome gains. It is also pretty cheap if you buy it from Sheng at jdmhondaparts.com. Last price $255 I don’t think he carries the b17 model though.
I have my new Hi-tech headers(about 6" longer than stock) on and will be cutting off my cat and jury rigging my exhaust until my new RSR shows up. I’ll post the results on how much low end I loose from missing back pressure and how much I gain top end. I will also have my friend host my gen2 webssite that has pics of everything I have done to my car. I’ll post the URL once the site has been transferred.
For acknowledgements sake my friend Shin did most the actual cutting as it was his dremel and I was sick as dog and barely awake. He did an awesome job, I have a picture on my website but it doesn’t show great detail.
Anybody here modified an ITR manifold to fit an LS? I’m thinking of getting one for cheap and getting my machine shop to machine a flange onto it to fit. Will probably still end up being cheaper then a skunk2.