87 Stock TBI 350 air cleaner lid flip upside down? Does it help? does it hurt? good or bad idea?

[Keith Seymore]

GM spent millions designing this but your Uncle figured out a way to make it way better after just 3 beers.

Well said. Much more concise than my version.

K

 

[Matt69olds]

I’m betting the airflow needs on a mild small block are easily handled by the air inlet. Automakers spend millions on testing trying to find the best compromise between cost, noise, power and emissions.

Flipping the air cleaner lid more than likely does hurt power. Probably not enough that the “butt-o-meter” can tell, but probably enough it would show up on a dyno or timeslip. The noise probably makes the truck “feel” faster.

The air under the hood is much hotter than you would think, and the factory air ducting is far more beneficial than you would imagine.

It gets pretty hot and humid here in central Indiana. 95 degrees with humidity just as high isn’t uncommon. My 69 Olds has the factory W-31 style air scoops under the bumper, and has Holley Sniper EFI, with an Intake Air Temp sensor. The IAT always reads 8-12 degrees above ambient temp. I have a friend with a 68 Olds (almost exactly the same car) with a standard open element air cleaner, also with Holley sniper EFI. It’s nothing unusual for his IAT sensor to read 40-50 degrees above ambient temps.

The factory knew what they were doing when the designed the air intakes.

 

[Dooley]

Setup on my 1988 V30.
Big block.

 

[Big Ray]

we did that when we were kids to get a more muscle sounding engine noise...in the 70's.
It was silly then, it's silly now

 

[Bextreme04]

So, from an engineering perspective...

It is FAR more important to have a source of cool air for any kind of EFI. In a carbureted engine the latent heat of vaporization cools the intake air charge down to just above freezing regardless of what the intake air temp is. In fact, it is almost preferable to have a warm enough charge to get all of the fuel to fully vaporize rather than pooling in the intake. A TBI system is forcefully vaporizing the fuel by ejecting it in a spray pattern under high pressure and therefore doesn't take as much heat out of the air charge during the phase change. Port injection is the worst for this and does almost nothing to cool the air charge. It's one of the biggest reasons that modern vehicles with port injection use rubber or plastic intake components and take the air in from outside the engine compartment.

Engine masters actually did an episode on fuel temps and on intake temps related to overall power and found the same thing.

 

[Big Ray]

Love watching Engine Masters. Even Steve Brulee is surprised by what he's finding out. He's been working on and with engines for decades. He's forgotten more than I'll ever know.

 

[RecklessWOT]

I always ran mine flipped for years, or just used open element air cleaners. Now that I'm older I use it in stock form. Technically on paper it should create a little less power flipped (unless you have cowl induction then it's probably a wash), but I will still say to this day it does in fact sound a lot cooler (and that makes you think you're going faster lol). Power gain/loss is negligible either way, won't really hurt or help much either way, just sounds cooler. But I leave mine closed nowadays because technically it was designed that way and yeah cooler air makes more power whether I notice or not, and the filter lasts a little longer.

 

[GTX63]

My cliff notes based on doing it starting 40 years ago.
Pros-It sounded great.
Cons-No performance gain.
No gas mileage gain.
Increased bugs and debris around the filter.

 

[75gmck25]

I used to own a ‘69 Torino Cobra with the 428 Cobrajet Ram Air engine. It did not have a shaker hood like the Mustang, but there was a hole under the fixed hood scoop and it sealed the hood to the top of the air cleaner. With high engine vacuum the flapper pulled closed and the engine drew air through the air cleaner snorkel, but when engine vacuum dropped it popped the flapper open and drew air through the hood scoop. The only flaw was that the flapper opened when you turned the engine off because there was no vacuum to pull it shut. Not good when snow drifted into the open hood scoop and down into the air cleaner.

When that hood scoop opened and started drawing air directly into the holley carburetor it made a “whaww” sound every hotrodder could love. Inside the car it was a more distinctive sound than from the exhaust.

 

[Ken B]

Wow there is alot of knowledge in here.
Just reading while killing time at a pdr shop(paintless dent repair).

 

[RanchWelder]

I designed the engine air induction system for the GMT800 program (7 different powertrains), introduced in 1999. Most of the components are still in use today.

I can say with authority that you gain more from picking up the cool air at the front of the vehicle than by drawing hot underhood air. You more than offset any increase in restriction due to the ductwork.

I ran a dual snorkel setup same as what Craig 85 is showing, with a flat hood on my Chevelle for many, many (many) years. It was easily worth .2 sec reduction in ET, from 12 flat to 11.80's.

K

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That looks just like my Cutlass 442 without the Hurst Nose!

Man I miss white swivel Bucket Seats and a solid white interior...
This is not the hood owned, but it is the one I wanted for my ride:

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Yes, I was stupid and flipped my air cover because it sounded cool in 1990...
A very patient man taught me I was going to pool water in the soup bowl created and during heavy rains, it was possible to hit a puddle hard and flood my carburetor with water down the bolt hole and into the lower air intake cover. One big gulp and hydro lock... the end.
So I put it back... before I snorkel'd it the bad way... and replaced my inner fender well water shields using old inner tubes and zip ties.

The Chevelle SS we drove as teenagers had cowl induction and ran off vacuum from the 454 Qudra Jet. The flap opened/faced backwards, so it did not suck in water, when driving in the rain... opened at the windshield near the wipers. It only opened when you floored it... or at 80mph... Tires were comparatively cheaper back then too... the 70' SS was the ****...
There were 3-4 rock crushers laying next to the driveway all broken up...

 

[legozombie]

@Craig 85 or anyone else reading this, what is this part called? I can't seem to find it for my K20 or the air cleaner for that matter. I've looked up variations of snorkel tub and carburetor intake hose. I also think I'm just dumb however that's a different story

 

[RetroC10Sport]

@Craig 85 or anyone else reading this, what is this part called? I can't seem to find it for my K20 or the air cleaner for that matter. I've looked up variations of snorkel tub and carburetor intake hose. I also think I'm just dumb however that's a different story

Air Inlet Duct. Part No. 14024595 discontinued.

 

[sidschev]

mine is not flipped but cut. really had no choice the engine fire destroyed everything. so i modified everything. i like it. i dont worry about heat cause its not hot under that hood she has way too much air flow in the front..

 

[SquareRoot]

mine is not flipped but cut. really had no choice the engine fire destroyed everything. so i modified everything. i like it. i dont worry about heat cause its not hot under that hood she has way too much air flow in the front..

So the exhaust manifolds are just for looks?