I researched what cars came with the intake manifold spacer, and found two different part numbers of spacers.
17108-PGK-A00
2003-2004 Honda Pilot
2002-2004 Honda Odyssey
2001-2002 Acura MDX
17108-RDJ-A00
2005 Honda Pilot
2006-2008 Honda Pilot 4WD
2006-2014 Honda Ridgeline
2003-2006 Acura MDX
Aside from the price, I couldn't find out any difference in the parts. The PGK costs $44, but the RDJ is only $23. After looking back here, I think I found the difference. The PGK has knubs that stick out, and have threaded holes. The RDJ, of which is pictured above does not have these knubs. However, the car I took mine from (2003 Honda Odyssey) did not have anything attached to them. After milling down the spacer, the knubs interfered with the fuel rail, so I sawed them off.
Here is how it looks before the spacer:
After:
Here is where the spacer sits, right on top of the intake runners. Before:
After:
Those pictures were taken with the standard sized studs still in place. I was smart enough to grab the studs from the Odyssey the first time I went to the junkyard. Here is a comparison.
What a difference!
Unfortunately, I didn't think I needed the bolts from the Odyssey because I thought they screwed into something else I guess. So I needed to take another trip to the junkyard to grab these:
The spacer was too tall stock, so it had to be milled down, I already knew this from the start. I test fit the manifold with spacer before milling it, and was surprised to see the hood actually close without bulging. Clever placement of an iphone in video mode showed that the hood was resting on the manifold when closed. It needed to be milled. Milling this thing was a huge PITA until I made a somewhat obvious yet brilliant revelation. Screw the friggin' clamp that required a ridiculous amount of leveling to get to an acceptable level. Just take the damn thing off and set it on the mill's table directly. Voilą! No leveling needed! The spacer I got was about 1.55-1.6" stock, and we milled it down to about 1.3". On driveaccord I heard most people were using .75-1" spacers, so more torque for me!
Here is the spacer milled and de-knubbed:
After getting the correct bolts, the spacer was ready to go on. Or was it...? That little extra height added by the spacer caused three major problems, and one minor one. First, the connector for the variable intake motor was not long enough. Thankfully after some not-so-careful tugging, it gave the extra room needed to reach the plug.
Here is the plug in question, and a good picture of how the spacer fits in there.
Second, there was some sort of sensor attached to the back of the intake manifold that no longer cleared the strut tower bar. Again I shall use the words not-so-careful to describe the solution to the problem. Bang on the bracket with a hammer till it was bent enough to clear the bar with some room to spare. I need to remember to not back up too aggressively or else the engine may pitch forward and take out that sensor.
The third problem was not so major, but it did prevent my car from going back together for another day and necessitated two trips to the auto parts store. This problem was a coolant line connected to the throttle body. With the added height of the spacer, the line was too short and would not allow the throttle body to reach the height of the manifold. After a new hose from the parts store, my dad discovered the old hose clamps were not sufficient to hold on the new hose. Cue the second trip to the parts store for proper hose clamps. I removed this exact hose on my 4 cylinder accord and it resulted in air getting into the cooling system and overheating the engine, so I remembered to bleed the cooling system this time.
The last, and thankfully, minor problem was that due to the added height of the intake manifold, the intake hose leading to the throttle body would be more likely to tear because of the awkward angle it is stretched at. I simply unbolted the airbox and pulled it slightly further away from the downstream intake piping to give it more room. I later reattached one bolt because the airbox was rattling.
I got the car back together after two days of downtime, bled the cooling system and took it for a ride. First impressions are that there is more torque at low rpm. Can't say anything about higher rpms, since I never got above 3000 rpm. It could just be that I was driving a miata around for two days, but I think it did improve low end torque. On one of the usual hills I go up at 45 mph in 6th gear at 1500 rpm, I usually have to really put my foot down to maintain speed, but with the spacer installed I didn't have to. After I got back from my test drive I discovered that the bolts holding on the throttle body were only finger tight.
I tightened them up and haven't driven it since.