Open Element question

[someotherguy]

I believe Someotherguy has said that GM used the inner ducting early on, and then dropped it.

Yeah, years ago I got in a debate with someone on FSC a while back about it, because I mistakenly assumed the earlier trucks were like 94-up, just open inside the fender. The earlier trucks in fact have a piece of plastic ductwork inside the fender that some feel is a restriction. It's fairly easy to remove; has a push-pin in the mouth of it and a single screw up near the battery, grab it with vise grips and snatch it out as it's slightly flexible plastic. Pretty sure I checked a few 93's I had on the lot at the time too and determined 88-92 trucks were the ones with this piece, hence the captioning on the pic:

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Richard

 

[Caman96]

That is interesting. I never put much thought into how the air in the fender got there. I just pulled up some parts diagrams and it looks like that duct you drew the arrow to was used in both the TBI and Vortec trucks. From what I can tell it's just a short little piece that directs air into the fender cavity. But... It appears the TBI trucks got some extra ducting inside the fender that the Vortec trucks did not.

TBI 350 diagram:
https://nemigaparts.com/cat_spares/epc/chevrolet/53c-c/03/tc03-015/

Vortec 350 Diagram:
https://nemigaparts.com/cat_spares/epc/chevrolet/54c-c/03/tc03-035/

So Schurkey's "bigass plenum" assessment looks correct to me for the Vortec truck fenders, while the TBI trucks might have some extra potential restriction going on. I wonder if you'd see any improvement by removing the inner fender duct (part number 1 on the TBI diagram) and running without it, like the Vortecs do? Or is that piece necessary to secure the rest of the intake to the fender?

Another random thought... Is the cavity in the fender air tight? I'd imagine that cool air can get in there from places other than just the duct in the core support, at least with the Vortec setups.

The plot thickens...

I can see why they eliminated that part, looks too restrictive.

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[someotherguy]

I can see why they eliminated that part, looks too restrictive.

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Lower part still exists at the "mouth" end on the core support, but simply feeds into the open space in the passenger fender. Ductwork inside fender eliminated from 1993-up. It does seem the initial opening in it is the choke point in the system as all the other openings appear larger, but without actually doing some engineer-style math (which is above my pay grade) I don't think I could say one way or the other, but since GM ditched it, I don't see any harm in doing the same.

Richard

 

[Caman96]

Lower part still exists at the "mouth" end on the core support, but simply feeds into the open space in the passenger fender. Ductwork inside fender eliminated from 1993-up. It does seem the initial opening in it is the choke point in the system as all the other openings appear larger, but without actually doing some engineer-style math (which is above my pay grade) I don't think I could say one way or the other, but since GM ditched it, I don't see any harm in doing the same.

Richard

It’s funny I was just looking at the lower duct on my Vortec yesterday while grille was off(did 4 High Mod).

 

[RichLo]

If you really want cold fresh air in the fender, you could attach a Fiero style side scoop to the fender...

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[Pinger]

Right at the front of the truck though is a high pressure zone which will aid the air's passage through that initial duct and into the fender cavity.

 

[PlayingWithTBI]

TBI 350 diagram:
https://nemigaparts.com/cat_spares/epc/chevrolet/53c-c/03/tc03-015/

Vortec 350 Diagram:
https://nemigaparts.com/cat_spares/epc/chevrolet/54c-c/03/tc03-035/

So Schurkey's "bigass plenum" assessment looks correct to me for the Vortec truck fenders, while the TBI trucks might have some extra potential restriction going on. I wonder if you'd see any improvement by removing the inner fender duct (part number 1 on the TBI diagram) and running without it, like the Vortecs do? Or is that piece necessary to secure the rest of the intake to the fender?

That would help, I guess, removing part #1 but, IMO the port and part #22 still look fairly restrictive to me. Plus, the port is pretty well blocked off by the grille and light lenses.

Further testing is warranted here, between IAT and MAP feedback, we may find out. Or at least, maybe see a trend. I know my truck runs better with cooler ambient temps. When it's 100° plus around here, not so much

 

[df2x4]

IMO the port and part #22 still look fairly restrictive to me. Plus, the port is pretty well blocked off by the grille and light lenses.

True, but... I think Pinger may be onto something. That port may not be as restrictive as it looks if the truck is moving.

Easy fix for the grille/lights though, just remove the high beam bucket on your passenger side quad beam assembly.

 

[454cid]

I'm not 100% sure I have the lower ducting on my 99. When I had my grill off last year for lights, I think it was just a hole in the core support. Now I'm curious..... but not curious enough to pull my grille on a cold cloudy weekday. I bought my truck at 6000 miles, so it's absence would probably be original.

 

[Caman96]

I'm not 100% sure I have the lower ducting on my 99. When I had my grill off last year for lights, I think it was just a hole in the core support. Now I'm curious..... but not curious enough to pull my grille on a cold cloudy weekday. I bought my truck at 6000 miles, so it's absence would probably be original.

I guarantee it’s there, unless your really looking, it just looks like a hole in core support. I don’t think light fixture would restrict it too much, it’s actually above opening. Once at speed, whatever available air is there would still go in, I mean even if it mounted on the grille face I don’t see it functioning that much more. I’ll go talk to the HVAC guys…….