[SD455DJ]

Originally Posted by Skip Fix

My 78 has had a lot of street miles as my daily driver years ago and even in the rain the open Shaker did not seem to be a problem.

I can see where just running through the snorkel would limit it. I'm not sure how much difference between the round 78 180 HP base vs the 220 hp oval base there really is as it takes an adapter to go from the round hose to the oval portion on the base.

Not sure if the larger "Dude Scoop" opening makes a big difference. I have one I've just never used it.

I agree...just breathing through either single snorkel is a choke point, but opening the shaker would allow ample air.

Dennis

[SD455DJ]

Originally Posted by Formulajones

I've never had rain hurt any of the cold air setups.

We were caught in a torrential downpour in dad's GTO, open scoops with the L88 setup, you can literally look in the scoops and see everything. Cruising along, never a problem.

Has never been an issue in my 70 RAIII formula either with it's front and center forward facing scoops and I've been in the rain in that car more times than I can count.

FJ, don't the Formula scoops have a vertical baffle an inch, or so, behind the RA grills along with a couple small drain holes directly below for any rain to drain? I always thought that removing that baffle would improve the ram air effect by providing a straight path vs. the 180 degree convolution the baffle makes the air flow around.

Dennis

[Cliff R]

The factory Shaker assemblies have PLENTY of opening to support big HP. The problem I found with them are that the later variety were redesigned and used a shorter top and it moves the air cleaner lid too close to the carburetor. I had both available to me when I was drag racing the Ventura and installing different engines and making changes to make the car faster at the track. The FIRST issue I ran into was trying to use spacers and/or taller intakes which required the shorter Shaker top and shorter air cleaner element. This INSTANTLY produced a HUGE hesitation/stumble/bog that would NOT tune out, plus "surging" in the mid-range and not able to get the engine to pull hard to the shift point.

If I removed the air cleaner top and ran nothing at all the engine ran fine everyplace, car left hard and it pulled right to the shift point with no issues anyplace. Any attempt to install an air cleaner lid on that shorter filter element and no-go.

So to run the RPM intake, for example I had to run nothing at all over it, seal off everything except the opening in the Shaker, and make a custom air filter for the opening. For many years I raced the car in that configuration, then decided to go back to the factory cast iron intake, no spacer, and re-installed the taller air filter and factory lid with the large rise in it. The car still ran just as quick everyplace without any issues anyplace at WOT and still only sucking thru the rear opening in the Shaker.

So there are some draw backs to some of the factory set-ups but the problems are NOT related to the opening in the Shaker not being large enough, at least from the testing that I did here with several varieties of them.........FWIW......

[Skip Fix]

One of the issues with the 78 types is even the metal that the fiberglass scoop rivets to does not have a really big gap around the filter lid for the air to get in.

The lean pop in face face at a dark track was quite a deal! Buddy even saw it in the stands!

[zippy]

Originally Posted by ta man

I find this calculation accurate. Also lid height over vent tubes makes a big difference.

Is that CFM or SqIn of filtering media?
Comes to 135 for my engine, yet a 14x3" filter only has 42 SqIn

[ta man]

Originally Posted by zippy

Is that CFM or SqIn of filtering media?
Comes to 135 for my engine, yet a 14x3" filter only has 42 SqIn

Area is diameter x 3.14 x height

[djustice]

Originally Posted by SD455DJ

FJ, don't the Formula scoops have a vertical baffle an inch, or so, behind the RA grills along with a couple small drain holes directly below for any rain to drain? I always thought that removing that baffle would improve the ram air effect by providing a straight path vs. the 180 degree convolution the baffle makes the air flow around.

Dennis

My '73 formula has a vertical baffle about 1-2 inches in, so there is quite a few turns the air have to make. First over the vertical baffle in the hood, then a 90 degree out of the hood down trough the rubber boots, and another 90 degree out of the boot into the aircleaner housing. Another curved 90 degree out of the airfilter and down the carburettor/throttlebody into the plenum, but that applies to all except velocity stacks. But it is atleast ambient air temp beeing fed to the intake.

[SD455DJ]

Originally Posted by djustice

My '73 formula has a vertical baffle about 1-2 inches in, so there is quite a few turns the air have to make. First over the vertical baffle in the hood, then a 90 degree out of the hood down trough the rubber boots, and another 90 degree out of the boot into the aircleaner housing. Another curved 90 degree out of the airfilter and down the carburettor/throttlebody into the plenum, but that applies to all except velocity stacks. But it is atleast ambient air temp beeing fed to the intake.

It sure is a convoluted path to get to the carb with a Formula hood!

Dennis

[steve25]

Some air cleaner flow rates done to SAE j726 procedures.

[Formulajones]

Originally Posted by SD455DJ

It sure is a convoluted path to get to the carb with a Formula hood!

Dennis

Yes it is, but with the testing I've done with it, at speed, it's very effective. I was having issues with the crank case filter element coming loose at the track. After every pass where I trapped over 100 mph that element would be laying right in the center of the back of the air cleaner. If I made a pass where I shut down early and didn't reach those speeds it would stay in it's holder. The air coming in at higher speeds was enough to lift that thing out of it's pocket. I ended up securing it with wire.

Then tried running the car without an air filter in place. That was a huge mistake. The car absolutely hated it. It backed up to the mid 14's after just running 13's the pass before. I could tell the first 600 feet or so of that pass the car was down on power. My guess is the air coming in was way too turbulent and it just screwed up the carbs ability to meter fuel. I put the filter back in and the car went right back into the 13's. I guess the air filter slows down and straightens the air path to some degree.
I've never experienced that with any other type of cold air setup on a car, they almost always respond well to no air filter if the base is left in place. Not the Formula, it hates no air filter.

[SD455DJ]

That is very interesting. I know that my RAIV judge runs 2 tenths and 2 mph slower if I close the scoops. So those small openings in the boundary (dead air) layer do have a positive effect...cooler air, not ram air.

Dennis

[AG]

The boundary layer is thin, probably only 10-15% of the entire opening of the RA scoop. You definitely are getting a ram effect of the air at 100 mph. If I remember correctly, it's about 2 psi at 134 mph, just use Bernoulli's equation to calculate it.

[Formulajones]

Yep, like I mentioned with dads 69, just those 2 tiny openings in the hood are all that's feeding over 700 HP and it seems to work. Well enough to go 128 mph in a 4120 lbs car. Those hood openings aren't even big enough for me to stick my hand in.

[steve25]

What I wanted to post back in thread 69.

[jhein]

I came across this article about Pontiac shakers. It mentions the differences in the lower air cleaner to properly locate the scoop. It also mentions the specification of a lower height filter to allow for clearance between the shaker and the air cleaner lid. So the fact that the TA air cleaner has a dropped base and a shorter filter requires the domed air cleaner lid to allow for clearance over the carb. Formula Ram Air lids are more-or-less flat. So if you put the taller filter in a TA, it will fit, but the lid will be jammed up against the bottom of the shaker and will not allow for air flow.

https://www.motortrend.com/how-to/04...r-hood-scoops/

"Contrary to what many believe, Trans Am-specific lower air cleaners are unique to Trans Am models due to the required drop producing specific scoop height and clearance. While appearing very similar, standard 4-barrel dual-snorkel air cleaners may not locate the scoop in the proper location nor produce the correct drop without modifications. Because of reduced clearance inside the air cleaner assembly, the shorter and smaller diameter AC A366C filter was specified as the original air filter used on all '70 1/2-72 Trans Am applications."

[Skip Fix]

Last night I pulled out of the attic and extra 180 hp base and a W72 base I'll take pictures of the snorkel and measure them . W 72 definitely a larger oval

[Skip Fix]

Here you go Dude scoop side and rear-forgot to measure the opening

[Skip Fix]

Here is a 180 HP base the outer round hose entrance is 4" OD 3.875 ID. Inner oval opening inside to the filter is 5.125" x 1.625". 8.328sq in
W 782 220HP maybe a repop round to oval adapter 3.75" OD , 3.25" ID. Outer oval opening where adapter fits 5.875x 1.875-11.01 sq in. inner oval near filter 5.875" x 1.75"-10.28sq in.

So does the slightly smaller round entrance restrict the W72 -8.29 sq in, vs the 180hp 11.75 sq in (or js ust this repop round entrance smaller, or does the smaller 180 oval entrance restrict it vs the larger.?

[Formulajones]

Those pics got me thinking, maybe just an illusion but those openings look huge compared to what I'm used to seeing. My Chevrolet factory air cleaners are no where close to that large, and I'm talking circa 1969-1970, not the smog era. I find that curious.

Here's a shot of the Z, with it's single snorkel air cleaner. That opening is shaped like a bell and necks down to only 1 1/2" !!
My Chevelle has the dual snorkel setup that was commonly used on LS6 Chevelles when cowl induction wasn't optioned, I simply removed the lid and put the seal on but if you can imagine a full lid on that air cleaner and only sucking through a pair of 1 1/2" openings, that's what they used on non cowl induction LS6 Chevelles. Not a lot of air flow there I would think.....

[Skip Fix]

Nice cars!