T/A KID

iTrader: (12)

Guys what is the purpose of the small holes in each of the 8 runners in the intake manifold?? I have heard they deal with smog? Also they may have something to do with the IAC and split BLM's? I noticed my edelbrock intake has them as well. But a lot of aftermarket intakes other than the LT1 do not have these nor do sheetmetal LT1 intakes I have seen.

Any help is appreciated

blkm6formula

iTrader: (2)

I do believe that is for pcv, but without having one in my hand I can not say for sure

SS RRR

iTrader: (2)

Indeed. It is a vacuum source for the PCV system.

speed_demon24

iTrader: (6)

Actually its for the IAC. The pcv is just a secondary function for it.

SS RRR

iTrader: (2)

Yep, forgot about the IAC. Those vacuum ports feed the IAC port, PCV as well as the ports on the sides of the intake. Don't think there's any "primary" or "secondary function"though.

speed_demon24

iTrader: (6)

Plug the holes and it won't run due to the IAC not getting any air to the motor. I think that would qualify feeding the motor air through the IAC its primary function.

SS RRR

iTrader: (2)

Fascinating. I never looked at it like that... and still won't since those ports supply vacuum for several other important functions. What you point out just so happens to be instantaneous. "Plug the holes" for the PCV or for a vented opti, maybe even the EGR solenoid and in a matter of time it could have the same effect.

T/A KID

iTrader: (12)

Thanks for the info guys. I have seen a modified LT1 intake setup for an airgap that had them totally removed? http://www.camaroz28.com/forums/show...+airgap+intake

Also From my understanding no other style of intake has them?? Makes me feel like there really not a necessity.

SS RRR

iTrader: (2)

First off let me clarify an error on BOTH speed's and my part- The IAC port on the outside of the manifold is routed into the plenum just on the opposite side of the wall that the TB mounts to. It does not use the vacuum ports on the intake runners. If you look from an upward angle looking down into the TB ports (with the TB off) you can see it.
Secondly from those pictures the only thing removed (at least from what I can tell) is the EGR port. The air gap still retains all of its vacuum ports on both sides of the manifold. I'm not positive, but I think ever LTx manifold has vacuum ports in the intake runners for a vacuum source. I believe the '94 intakes used a vacuum port on the drivers side of the manifold for a PCV source instead of below the TB since the opti was not vented. This is a stretch, but I also think the '93 intakes did not have an IAC port at least routed into the plenum.

1SWT95Z

Have you guys ever heard of casting problems/differences with these holes causing split BLMs? Or the IAC ports not lining up correctly with the throttlebody causing split BLMs?

T/A KID

iTrader: (12)

My buddy has an 93 LT1 intake and that intake has the runner holes as well. Overall I like the design of the 93 intake better than the 94-97 LT1 intake in respect to the actual intake manifold.

IF you take the 4 threaded Npt fittings off the bottom of the intake they open up to the small holes (2 from each runner)
The thread I listed above has all of the vaccumm ports on the side of the intake but no longer has the PCV setup on the side or front, and since he done the airgap the way he did, he is no longer using the holes in the runner.

GMRL

Im pretty sure those are there to hold the injector covers on the Vettes.

hyperzone

If anybody needs a visual on these "holes"... I posted some pictures way back when I was wondering what they were for.

Heres a thread with some pics

T/A KID

iTrader: (12)

If that is the case how do single plane intakes and other intakes for the LT1 idle correctly without these holes in the runner???

Formula350

iTrader: (3)

I'm not seeing the holes in the external pic from the first page of the home-made air gap. Even the underside I don't see 8.
http://www.lt1intake.com/images/L99%20intake.JPG
Other than that. I see 4 bolt holes, 2 between each injector bung on both sides. Then 2 more up higher on the plenum on each side. Under then is just those 5 NPT plugs. Where are these 8 you're seeing? :\ The only 8 holes (one in each runner as you mentioned) are the ones for the injectors

hyperzone

^^^ formula... look at the link in my above post.. I posted some pix in another thread and mentioned these holes.. you only see two or three of them in my photos but, there's one in every runner. Its not just the injector holes.. the ones they are talking about are on the bottom side of each runner.