Well it dawned on me today, that i never really thought about what those small tubes on each side runner are for. I see from porting the plenum that one side is through to to 2 holes just inside the front of the plenum, and the other side is from the triangle shaped hole between the throttle bores. They follow and enter into the intake base, but then what? then where? Are they purely vacuum or do they flow air? i almost feel embarased to be confused about this hahaha.


And a side question...

Whoever had put plenum to runner gaskets on the car before me mixed them up, and the holes for those small tubes became about 75% restricted by the offset gasket. Could this of messed with something? My whole intake, base, runners, plenum, TB, were filthy with black soot. like carbon buildup i guess, and very hard to wash away. could these holes being blocked casue this black buildup?


thanks for anyone who can tell me something about this, it is appreciated.

 

The small tube is for the egr system, not sure how the system would react if the tube was partially blocked.

 

Both of the gasket sets I have installed on my TPI had that small tube hole in the wrong location and covered the hole about 75% up as well. I dont know why, they were installed correctly.

 

just EGR passage. even if you had GM gaskets, installed by GM, most did partially cover the holes. This is because even GM wasn't worried about the "port match" of the egr passage. Also the carbon you noticed caked on everything is due to EGR.
egr (exhaust gas recirculation) = carbon dumped back into the intake

 

Yea this all makes sense. The black carbon crap is very hard to clean off, especially in places where i cant reach with somehting to scrub it off. Does anyone know of some sort of cleaner which has been able to break it up and remove the carbon?


Oh, and when I replaced the plenum to runner gaskets, the egr holes did match up almost perfectly, when they were flipped to the wrong sides they were blocking the holes.

 

2nd post

http://forums.corvetteforum.com/show...24&forum_id=48

 

Systems that run no EGR also build up varnish in the intake. It isn't all due to EGR gasses.

 

I imagine PCV would draw plenty of gunk in there also.

 

The EGR system has no feed back to let the ECM know that exhaust gases have actually been recirculated. The EGR system reduces NOx emissions, but there isn't a NOx sensors on our cars.

 

True even a carb from years ago builds up varnish, hence carb cleaner works miracles on. TB cleaner is supposed to be slightly different somehow. Both will clean the varnish buildup easily.
That crap the EGR adds to the mix can get hard as a rock. Literally
have to chip it off and as said sometimes it is in a not so easy to reach place. Have had intakes chemically dipped at my job where we overhaul JET engines and have chemicals that will DISSOLVE
aluminum and some other types of metals and that carbon is a tough one to remove. Hence do yourself a favor and get rid of EGR altogether and tune it out of your computer. I know you are a proponent of EGR but no one will convince me hot dirty air REintroduced into my engine to combust is a good thing.