milling out the factory casts in the plennem

[captbane]

hi all! im running a 1989 coupe (auto) with an open k&n airbox,enlarged intake has been cut through the front of the frame to come out where the lic.plate would be, high pro.dis. and coil,a flow foil in the intake tube,hypertech theremomaster and 160 thermo. ex. is stock 1991. this car really flys for the motor in it, i have no idea what else has been done because i bought it from a dealer, i havnt cut out the mass air flow screens yet(good idea? bad?) but ive been told there are 2 half moon castings inside the plenem that would greatly increase hp if they were removed. anyone ever hear of this? tx all! see ya on the road! dont forget to wave! capt bane

 

[Ken]

Welcome To The Corvette Action Center captbane!

Glad to have you with us.

Sounds like you've got all the pieces in order for getting fresh air to the engine, I hope it can exit as easily.

I have heard about the casting shapes of which you speak, but can't remember at the moment where it was I saw it. At any rate, in most cases, it's always best to have the passages as smooth as possible for a clean airstream to the cylinders. I certainly cannot see a reason for not removing them.

As for the "greatly increased" horsepower... My guess is that it would be more like one or two, maybe five, horsepower; it's all contingent upon the performance capabilities of the rest of the engine parts.

 

[RoadReady]

Never heard of cutting the MAF screen out, but just cleaned my throttle body (wow, what an improvement) and found quite a bit of trash on the screen!! Can't imagine how it got there since the air intake system is stock and the filter was seated correctly. Still, I had to use a toothbrush to get it out of the mesh. Suppose a piece of trash could damage the MAF wires?

 

[Edmond]

Never heard of cutting the MAF screen out, but just cleaned my throttle body (wow, what an improvement) and found quite a bit of trash on the screen!! Can't imagine how it got there since the air intake system is stock and the filter was seated correctly. Still, I had to use a toothbrush to get it out of the mesh. Suppose a piece of trash could damage the MAF wires?

I don't think a piece of trash big enough could get to the MAF wires. But if it were small, the MAF would burn it off after you turn the car off.

 

[captbane]

re: on topic start

Thanks for the input all!! Cleaning the t-body sounds like a good idea too! What did you use? Capt Bane

 

[RedRagTop]

Interesting. Guess I better check mine after it comes back out of storage.
www.c4vettes.com makes some serious claims in HP gain for some of the mods you mention but I take them with a grain. Mine has K&N, cut lid, chip, free-flows and I'm sure it made an improvement. I have yet to pull the corvette challenge MAF screen removal as I'm nervous about the horribly expensive MAF wire being damaged. The screens must be there for a reason...

 

[Edmond]

The screens must be there for a reason...

I believe the primary purpose of the screens is to smooth the air flow as it passes through the MAF.

 

[Moonunit 451]

Hey Captain, welcome! I just took a good close look at the plenum off my 86. There are several "half moon" protrusions in there, but the are all smooth and clearly are there fo securing bolts that attatch the runners and other items to the plenum. I suspect that they are nessecery (sp) to keep the threads from stripping. Surely the bolts associated would protrude into the plenum in each case. Hope this helps

 

[bill mcdonald]

hmm, never heard about removing and half moon shapes.

I have heard about cutting out the intruding walls directly behind the throttle body, and smoothing them out for more flow though.

I went about on my aftermarket intake and removed all the casting flash I could, base, plenum and runners.

 

[Eagle85C4]

Well let me put this to rest...

Yes there is 2 half moons behind the throttle body in the plenum.
The reason they are there is to provide a venturi effect for the 9th injector. Close observation to the holes directly behind them lead you to the injector.
I used a hole saw to remove both of them, then dremeled the area to smooth it out below the throttle body holes. I then continued and removed every bit of protruding aluminum in an attempt to polish and port the plenum.
I placed the stock gasket on the edelbrock runners, cut out the excess material over the holes to smooth it out, then placed the gasket on the plenum and opened the holes to match the runner, this is called port matching. The same was done for the intake as well.
It did make a big difference. Smoother running and it revs up quicker.
My advise....cut away....

 

[Mad-Mic]

i descreened my MAF earlier in the spring and have had no problems at all! i did the MAF, cut lid, K&N filter, and TB Bypass all in the same day. i could tell there was a big difference in HP. Definetly pulled harder

with just some very minor mods and alot of tuning i'm running 13.2's-13.3's very easily. i'm trying to crack a 12.9x on a stock TPI motor, trans with stock 1600 stall, stock 2.59 gears. i think it is very possible! look at my mods below for details about my car

 

[captbane]

port matching

port maching is something ive heard of, and in the spring im going that way too along with the plenum smoothing. thanks all for the valuable input to my orig. quest.!! see ya on the road !!