I was talking with my friend who has owned quite a few LS cars in his day, and now owns an LS2 C6, and he was mentioning that there were some decent gains to be made on the LS2 by cleaning up the intake manifold runners. Basically, where the plastic pieces of the intake manifold are glued/welded together, they didn't do a very good job lining them up, so there are ridges and edges sticking out into the runner. By going in and just cleaning up the ridges and basically smoothing out the wall, he claimed people have seen some really number good increases from this (5-10 whp).

I came home and looked at one of my manifolds, and the HR intake manifolds have the same ridges (see image below). I was wondering if anyone has played around with cleaning up these edges and have some good comparison numbers?

 

I obviously haven't tried it yet but from my reading of other people doing it on a Z32 when i had my Z32, they have made the same claim about grinding down and matching the upper and lower plenums. Same concept me thinks.

 

thse 2 pieces arent that bad, you should see the fitting bettween the upper and lower intake manifold. !!!

 

I have also heard from various people both internet and person who are very car-tech savvy and they say that the manifolds are designed that way to cause the air to, for lack of a better term, swirl and mix better with the fuel. However this is just hear-say, and i have noticed gains from people port matching them.

 

Extrude Honing:

http://boneheadperformance.com/extrude-honing/

 

You want a swirl and tumble effect in the cylinder, but not in your manifold. Turbulence in the runners will effect the pulses the engine *should* be designed to take advantage of.

 

Wow! I hadn't looked at that. I will say, some of the misalignment I have seen with the two pieces of the upper manifold have been rather large. This one is about 1mm, where the largest I would say is 3mm. That misalignment of the upper and lower manifolds looks to be about 2mm per side, which is awful. Thanks for sharing this picture!

 

keep in mind I looked at both HR and VHR upper / lower intake manifold.

They are all the same. Speaking of the fitting but not the runners lenght or bolt pattern.


this picture is when I was finish with the matching of the port.

 

I know what I'm doing this weekend lol

 

if you have the time, everything should be gasket matched

 

the problem with the HR/VHR is that you cant really do this gasket matched thingy
because the gasket is squares of flexiable rubber.

so the only way is to remove the lower intake manifold and scrach with a small scribber the aera to remove on the intake runner lips with a dremel or something

 

I'm lost....

are we looking up through the runner into the lower intake manifold?

Also how are you filing it even?

 

both pictures I posted is a view from where it would meet the head.

the lower intake manifold is like the cast alluminum and the upper intake manifold is the black looking part ( plastic )


and like I said in my previous post , I used a scriber to scrach on the side where I would need to dremel the side of the plastic port.
it took a couple hours doing it

 

My original picture was looking into the runner of the upper intake manifold. Nissan injected multiple pieces for the plastic manifold, then glued or plastic welded the pieces together, which is very common practice for plastic manifolds. The problem is the pieces don't fit together very well, so there would be a performance benefit from smoothing out the ports by removing material at the misalignment. I was wondering if anyone had tried it, and how much there was to gain.

 

So I'm attempting this now and it's pretty straight forward on filing and smoothing out the differences...

Who would have the ***** to trim down our stock mainfold

From


To this


From looking at the bottom, it looks like it can be done?

 

Whoa is that even the same manifold in the second pic?? Looks like a completely different one rather than one they shaved from the OEM plastic..

 

I know one of the guys from Polk Performance when they were still around back in Arkansas mentioned doing this and finding some gains but I never went through with it. Ill be interested to see what others find out.

 

Slightly different but it's basicly a skeleton of the stock one

shoots as a few post above mention. If there is anything to gain it a well worth mod!

 

I'll post pics when I get off work...

Even if this mod only yields 1hp...was easy and worth it to me. Forget what I mention about cutting it up to look like the manifold posted. After looking into the manifold from the TB side it's all one open piece. You CANNOT trim it down.

 

Ive always wanted to somehow split the plastic manifold in half (top and bottom) and add like a half inch of plastic between the two then plastic weld it back together haha.
Then run two 09+ maxima TBs with bigger intake piping (plastic, not metal) going to the stock air boxes with TiTek ram air scoops feeding directly into the air boxes , also my filters would magically disappear at that point. Just for ***** and giggles of course