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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
I know this sounds more like a 'body part" category, but it relates to engine performance. Seems to be some controversy on the function of the power bulge hoods on the early 3rd gen. T/A,s, and the Formulas. Could some of the members elaborate who actually have one, and driven them, give their opinion on their experiences? They are the ones that are open to the air cleaner housing, and curious if anyone has had any performance issues with how their engines ran. "Big power", runs like a raped ape", or, "got sucked into my motor, and fodded out the eng.,", or maybe.."doesn't make a damn bit of difference, on the street". just curious if anyone has their druthers. Thanks.
So I got mine working on my 83 T/A, and i added an LED strip on the cowl so i can see when it opens and closes while driving.
My biggest surprise was how seldom it opens, and how short it stays open. I did some testing on the vacuum switch, and the switch only closes at damn near 0 HG and opens again at 5-7 HG.
So this means that the engine needs to not only be at high throttle, but be under a pretty good load for the flap to open. It usually doesnt open for me in 1st or 2nd gear, even romping on it.
That said, does it make a difference? The butt dyno says yea, it adds a little kick. Earth shattering power? Nah, but its pretty cool, i like having it, and showing it off and explaining to people how it works.
Its not adjustable. I toyed with the idea of adding an adjustable to get it to open more and longer, but havent, just have it working the way it was designed.
I found an adjustable vacuum switch for a 700r4 trans that might work, was looking into it.
Again, would it make a huge difference? Nah probably not. You probably dont want it opening except under heavy load anyway. But would be something cool to experiment with.
Tinkering is the fun part of the hobby. I wish my car was at the point of tinkering. Still in the "get it together" stage, but you know what they say. The journey is 1/2 the fun. LOL. (They haven't heard what comes outta my garage, when I'm working.)
The functional mechanism only existed from 82-84, then the hood went away until 1987. When GM revived the hood on the 87 Formula, through 92, there was no functional feature, and a block-off plate was used, making the bulge purely ornamental.
Too bad, too, because it would've been a nice feature on Formulas with LG4 and LO3 engines that would've set them apart from, and given them a slight advantage over, Firebirds and Trans Ams that received those same base V8 engines.
I've read that some people with LG4 and LO3 engines have gotten the parts to make their hoods functional; I would've if I had one of those engines. And I've also read that some people have propped open the flapper for functionality 100% of the time, but I think that was only after their vacuum solenoid failed, or simply to avoid trying to install a vacuum solenoid when adding the feature to their hoods.
It apparently worked well enough to be recognized by the butt dyno, and lightweight debris, such as leaves, could be seen getting sucked up against the grill screen in the bulge.
Camaros had the openings above the headlights for direct intake airflow, but Firebirds didn't, so that functioning bulge gave Trans Ams their own direct intake airflow.
Id definitely be worried about water getting in if it was blocked open all the time. One pop up storm and your carb is sucking water like...I dunno a fish or a dolphin or something. Maybe an elephant.
The 2nd gen T/As went back and forth with their shaker hood. same principle, pulling high pressure air at the base of the windshield. My 73 had the plate removed, and I drove it daily, with it open. Rain or not. When it rained, you could see a few small droplets entering the scoop. Never did any damage, or created any problems. . Call it a "natural" water injection system. Even had it's own drain tube from the air cleaner base.Just like the early 3rd gen functional one. Has it's own plastic trough, to catch water, and drain it down and away. With the 3rd gen T/As, the carb is centrally mounted, and the hole on the top of the air cleaner is sealed with a small 4" opening, and offset. (The pic below, I can't delete or move, cause it ended up where I didn't want it. It shows the limited clearance with the factory Air Cleaner of my 301 turbo eng. The hood won't shut. Where do I go to delete, or move the photo down?)
. Maybe that isn't perfect, but it's gutta be better than sucking in hot underhood air, even from the fender area. For a daily driver, that's not tuned for it, Probably doesn't matter a ton. but if you're gunna drive a performance car, isn't it nice to have one functioning, if it's available, reasonably?
My 301T turbo project car puts the carb right under the bulge. But because it's so much higher, complicates the plastic pan. Mods are necessary, but will be completed, just because.
Man, did this post get screwed up.
Last edited by tajoe; Oct 27, 2022 at 10:19 PM.
Reason: other
On these cars the dual ducted air cleaner with the twin air inlet ducts to the top of the rad support works as good or better. No opening mechanism required. This cold air "ram air" ducting picks up cool dense air from the front of the car.
The rear opening of the power bulge hood is not close enough to the best area of the base of the windshield like the old 60's camaro, chevelle and vette "Cowl Induction".
a NOS system WOT throttle switch on the carb linkage operating a common A/C solenoid could be wired to open the flap at any throttle position that makes you happy.
More show than go on this one.
Might be cool to custom mount a AFR or a manifold vacuum LED strip display guage on the rear facing block off plate.
Last edited by F-BIRD'88; Oct 27, 2022 at 10:21 PM.
Can you modify the air cleaner to mate up with the hood bulge? Kinda like the image below. I’ve seen this done on race cars but don’t have pics. Found the one below on this site but it’s on a camaro.
Can you modify the air cleaner to mate up with the hood bulge? Kinda like the image below. I’ve seen this done on race cars but don’t have pics. Found the one below on this site but it’s on a camaro.
Another good idea, and another thanks. appreciate the tips.
Does Edelbrock have a good intake for the naturally aspirated form of that engine?
You maybe could get much better throttle response and a lot more power by using that type of intake with an elbow and a modern approach to turbo induction layout. And you know.... Maybe close the hood too.
Now that's thinking outside the box. I do have a N/A 4 bbl intake for a 301, but the entire purpose of my build, is to use the original turbo plenum, as designed by the engineers, just for the "nostalgic" look. what they had at the time. The hood does clear the carb., just not with the factory cold air package made for the N/A 305 air cleaner.
I'll just have-ta fab something else to seal the carb to the hood. I'll be digging thru my scrounge parts to see what's lying around, that might work. I'm leaning towards the system that Battman posted above..
But thanks for your idea.
Even had it's own drain tube from the air cleaner base.Just like the early 3rd gen functional one. Has it's own plastic trough, to catch water, and drain it down and away. With the 3rd gen T/As, the carb is centrally mounted, and the hole on the top of the air cleaner is sealed with a small 4" opening, and offset. (The pic below, I can't delete or move, cause it ended up where I didn't want it. It shows the limited clearance with the factory Air Cleaner of my 301 turbo eng. The hood won't shut. Where do I go to delete, or move the photo down?)
