After a rain, the carbureted V8 in our Ford station wagon seemed to have more power!

Was water in the air turning to steam in the cylinder combustion and creating more force?

Should we inject a tiny amount of distilled water to gain more pressurexpansion in the cylinder?

Thank you.

If I remember correctly, Tom and Ray Magliozzi used to recommend spraying a small bit of water into a carburetor to get rid of carbon buildup that could cause pinging and dieseling (continuing to run after you shut off the engine).

If that’s what’s going on here, the smart move would be to prevent carbon buildup by regularly replacing your fuel filter and air filter, using top tier fuel, and occasionally spraying some carburetor cleaner into the carb with the engine running. If the gain was that noticeable, you might benefit from a full carburetor rebuild. It also might not hurt to pour some fuel system cleaner or carburetor cleaner in the fuel tank every few months.

I wouldn’t make a habit of deliberately introducing water into the combustion chamber, because you could easily hydro-lock your engine if you use too much.

Most people want to keep water out of their engine, you are the only one I know who wants it inside the engine.

The air is cooler and denser after a rain providing a lot more air molecules than warm air would (up to a point). More air and you have a better running engine.


Water in the air is already water vapor, so it doesn’t turn to steam in the combustion chamber. Your carb is set up for ‘average’ conditions, it can’t adjust much to changes, so maybe the combination of conditions after a rain is slightly better for your wagon, as described by @kurtwm1 above . Or maybe it just seems that way.

This was back in the late 1960s.
Mother first noticed it on her own. Then when I attained my driver license, I.ndependently noticed it.
Already being water vapor, I could not figure how the H20 could further expand.

Afterains, I considered cooler air being more dense. But when I drove into low areas where the air was much cooler, I did increased power even though expecting it.

There’s also more wind resistance with denser air. If the road is wet there is more rolling resistance.

Some aircraft in WW II were equipped with water vapor injection to increase horse power and for years J.C.Whitney offered a contraption for injecting vapor into the intake of cars. I’ve seen a few of those installed and it was a crude contraption.

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I seem to remember in the 60s and 70s a few of us thought cars ran better in the rain. No verifiable evidence on my part.

Water vapor is a gas. If you heat water vapor you get hotter, expanded steam.

What the water injection into the engine does is cool the intake charge because its temp when it enters the engine is lower than the combustion temp so it makes more power.

Early turbo engines - the Oldsmobile 215 V8 and the Corvair Monza both had water injection as standard from the factory. People forgot to refill the water, a lot.

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Pretty sure water injection systems injected a mist of liquid water, the benefit was in the heat absorbed as the water drops were vaporized.


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Yes, they definitely did squirt liquid water but turned to vapor in the hot, compressed air in the manifold before even getting to the intake valves.

No intercoolers back then

Wasn’t it special colored water that the dealers sold at a pretty profit?

I remember when the 63 Corvair Monza Spyder came out. I was driving a 56 Studebaker Commander and the kid in the Monza challenged me at a light. My $45 Studebaker ate the Monza’s lunch.

The day after I threw a rod in my 56 Desoto, I set out on foot to find a car with $50 in my pocket. I walked down Hertel Avenue and then North on Delaware ave in Buffalo. There were a lot of car dealers there. I goy to Delaware Motors and they were in the middle of moving there car lot when I spotted a lonely Studebaker against the back fence. It was a 4 dr with an ugky combo ao faded yellow and brown rust and the headlight rims were missing.

When I asked the price, they said they really did not want to move it so they would take $125 for it.I told them I only had $50. They said they could not sell it for that, I said I am not arguing what it is worth, just telling you that I don’t have any more.

Isaid, I may be the only person in the world that wants that car and the junk price is only $25. The agreed to sell it to me for $50 but would not inspect it. I said I could only give them $45 because I would have to pay for an inspection. The salesman said, fine I will take the $45 but I don’t want to see you or that car again.

The key did not open the trunk and when I got home I forced the ytunk and found two Atlas snow tires that had never been on the ground.


I spent a lot of my childhood on the stretch of Delaware Ave. between the main entrance to Forest Lawn Cemetery and the Delaware YMCA just south of Kenmore.

Cybercruising the neighborhood on Google Earth, it looks like the neighborhood hasn’t changed all that much. The names of the businesses along that stretch or road have changed, but not much else.

In the 1950’s and earlier among performance enthusiasts/geeks kits to inject a little water spray into the carb were a known way to get more power. You could buy them at right out of the JC Whitney (super popular auto parts catalog pre-internet that all us older guys will remember) catalog.

As for the rain and power boost, well known. In the country and western song “Maybellene” by Chuck Berry here are the relevant lyrics: :wink:

“…I saw Mabellene in a Coup de Ville
A Cadillac arollin’ on the open road
Nothin’ will outrun my V8 Ford
The Cadillac doin’ about ninety-five
She’s bumper to bumper, rollin’ side by side
Maybellene, why can’t you be true
Oh Maybellene, why can’t you be true
You’ve started back doin’ the things you used to do
The Cadillac pulled up ahead of the Ford
The Ford got hot and wouldn’t do no more
It then got cloudy and started to rain
I tooted my horn for a passin’ lane
The rainwater blowin’ all under my hood
I know that I was doin’ my motor good…”

If you google
carburetor water injection
You’ll find dozens of kits for sale.

Water injection was used in aircraft engines in the 1940’s.

… and many other places for the techi details on how water injection (with or without methanol in the mix) improves combustion. The gains are substantial enough that it’s worth doing. But then there’s the PITA of keeping a water reservoir filled. And offhand AFAIK is only easy to do with carb cars :thinking:… and nearly all of ours here are fuel injected.

Water injection can also improve MPG.

I don’t think humidity will do anything.
The water has to transition from liquid to vapor to get the cooling effect.
In the case of rain it’s tiny droplets of mist going into the intake.

In the Clark Gable/Barbara Stanwyck movie “To Please a Lady” Gable waits to just before the rain starts to make his Indy 500 qualifying run.
Starts raining just as he completes his laps.

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