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I have the original air cleaner system on my '78 but I see a lot of cars here with the open air cleaner.
Is this something I should swap out? Does it make much of a difference? I need a pic of the engine....will get one soon.
Those in the know claim the stock airfilter with the cold air intake works the best.
most of us go to a open airfilter for looks or because of high rise intakes. Completely non stock engine setups, Completely different carb or throttle body's.
In the beginning I lost the stock airfilter for reasons of looks alone.
if you remove all the heat riser tins from the left side of the engine be mindful that you will need to install the J shaped heat shields above the spark plugs like the right side has or you will be burning spark plug boots.
Those in the know claim the stock airfilter with the cold air intake works the best.
One summer maybe 40 years ago I bought an open chrome air filter. Looked great....old school.
That Fall when the air turned cool I thought I'd put the original system back on & see if I could feel a difference.
It's been stock ever since....
Performance is improved with cold air intake vs hotter engine compartment air. 78 L82’s dual snorkel intake worked so well compared to L48, GM used the dual snorkel for both engines in 79; claimed 5hp gain. If you have L48 switching to dual snorkel requires a different AC line from back of compressor; and they are hard to find. I went with a custom fiberglass CAI sold by a CF forum member on fleabay as rfengineer21. It only fits electric fan conversion, not stock fan shroud. He’s made 100 of these and is on about the 6th version of tweaking the design.
Charlie
The dual-snorkel system works great, if that's what you have. The single snorkel (which I think was used for both 78 and 79 L48s), not so well.
Please post some pics!
I converted my 79 to a dual snorkel system to match my 80, and tossed the stupid aftermarket system that a PO had installed. Both cars have full cold air all the time, with no provision remaining for heated air or flapper valves.
Here's a graph that shows the difference between ambient engine compartment air and what the carburetor injests through the CAI system. Note that to make the most of this difference, you need to tune for it, or ideally run an EFI system. Prior experiments in my 79 showed an even greater difference.
IMHO, the factory air cleaner only works if the cold air tubes are installed to the get the cooler air in. I like the chrome open air cleaner so I can hear those carb secondaries open.
Its been said for several yrs that the (almost) cold air duct is worth 5 horse.
But that's at the flywheel. Then, you have to deduct 17% due to drivetrain friction, to achieve the rear wheel horse.
So, what are you going to do with that, one horse gain?
Its been said for several yrs that the (almost) cold air duct is worth 5 horse.
But that's at the flywheel. Then, you have to deduct 17% due to drivetrain friction, to achieve the rear wheel horse.
So, what are you going to do with that, one horse gain?
That math looks backwards to me; 5-17%=4.15. By itself, insignificant; but combined with all the other “little tweaks” available with other mods, will add up. I can’t quote an exact episode, but Hot Rod Garage did an episode on exactly that. Before and after dynos showed a worthwhile(exact number?) cumulative gain with a modest list of modifications.
Charlie
Wasn’t the increase in hp claimed net?
also if u drive in winter the preheat is helpful. I think they wanted ideally 130f air and WOT opens direct cold air plenum..
in addition to bikespace readings here https://www.corvetteforum.com/forums...l82-4m-ac.html
Unless you run around at 5000+ rpm frequently to get that few extra hp, then it doesn't really matter which air cleaner type you use. You won't notice any difference at 2500 rpm. So put on whatever air cleaner that you think looks good on your engine.
Going to be hard to beat that duel snorkel air cleaner for performance reasons.
Me, I'd gut out, delete the hot air flappers. I never run in below zero weather. And those flappers are a bit in the way restricting flow.
Put a chrome lid on it if you want to pretty it up.
.Or rip it off for a much cleaner look. Maybe give up a couple high RPM pony's. But a much cleaner look.
You have what is called a TAC or Thermostatic Air Cleaner...
It is part of the emissions system and used primarily for cold starts.
On a cold start, under hood temp under 85* fresh air is closed off from entering the air cleaner and only pre-heated hot air from the stove pipe is allowed in.
There is a vacuum sensor inside the air cleaner, when that sensors temp reaches at or above +85* - 128* both fresh and pre-heated air are allowed to enter the air cleaner.
Under hood air temps above 128* only fresh air will enter the air cleaner.
That's the way it should work anyways...
You can see there is a vacuum actuator on each air inlet of the air cleaner, this controls the (flapper) on both the drivers side and passengers side.
On the drivers side, it also controls a gate that allows or closes off hot air from the stove pipe.
You can remove the flappers by driving out the hinge pins that hold them in place. Block the heat stove hole with aluminized tape and paint it. You can also remove all of the then redundant vacuum lines and TVSs. I've done this on both of my C3s that never see snow.
So a few years ago after pulling my rad and swapping to electric fans I decided to go for a drive with the hood still off my car... I was pleasantly surprised at the increase in power I felt with the hood off and cooler air getting pulled into the carb. (some of this was also from the freed up hp from the lack of the clutch fan drag)
So I built my own cowl CAI setup using a spectre piece. I wanted to make sure it was working so before I did it I installed a dual temp gauge with a thermister in the engine compartment down by the back passenger spark plug location and another sensor inside the air cleaner.
What I found was my new air cleaner setup keeps temps very close to ambient when the car is moving and while sitting still its still at least 20-30 degrees cooler than in the engine compartment.
upper temp is inside the air cleaner and lower is engine compartment at full temp just pulling away after stopping at a light. When moving on an open road the difference in temps climbs I do not have the flaps installed above my control arm and I have open space between my hood and the top of my rad which normally isnt a great idea but I have a high rise hood and found the engine compartment stays cooler this way with my engine temp also still being consistent.
And no the gauges are not hindering air flow and the temp sensors are accurate. The vents in my hood are functional as well.
Last edited by augiedoggy; 07-19-2023 at 10:27 AM.
Performance is improved with cold air intake vs hotter engine compartment air. 78 L82’s dual snorkel intake worked so well compared to L48, GM used the dual snorkel for both engines in 79; claimed 5hp gain. If you have L48 switching to dual snorkel requires a different AC line from back of compressor; and they are hard to find. I went with a custom fiberglass CAI sold by a CF forum member on fleabay as rfengineer21. It only fits electric fan conversion, not stock fan shroud. He’s made 100 of these and is on about the 6th version of tweaking the design.
Charlie
Forum member Pauldana is the person who designed and builds these CAI’s.
He posted data in a thread several years ago and you can do a search to find it.
I have a highly modified engine going into my 73.
Once it is in and I can measure all clearances with my new hood, I hope to run one of these.
I acknowledge that cold air makes power, and as a result of that the factory setup is probably superior. However, I have a 3" open element air cleaner for two reasons. One, it fits over my Holley carb, which I can't say for the factory setup, and two, I like the way it looks with the hood open. And my 427 pretty much makes up for the 5 hp it's costing me.
07-08-2023, 04:46 AM
Air Cleaner
One summer maybe 40 years ago I bought an open chrome air filter. Looked great....old school.
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