Selectable warm and cold air intake.

[oil pan 4]

Winter is here and the carbureted vehicles that had a great lean burn turn in them are running very badly on start up.

Right now the air cleaner just draws warmed air from under the hood, it warm up eventually after everything else is hot. With the air heater tube going between the exhaust manifold and air cleaner I can have warm air less than 30 seconds.
The factory air cleaner is set up to run warmed air. All I have to do is hook it back up.
The way GM did it there is a pneumatic thermostat that opens and closes a flapper on the air cleaner intake tube. So it would go back and forth between 600'F air and cold air. You cant tune for that.
So I found a use for my http://ecomodder.com/forum/showthrea...ake-27400.html. Instead of running raw scorching hot exhaust manifold air to the air cleaner I will temper the air with this. Then the engine will have warm air that is about the same temperature all the time. I can tune for that.

Only problem is this thermostatic valve was built for a 1.6L gas engine, not the 7.4L that its going on.
So I will need to retain the cold air function.

I have a small 3 way vacuum solenoid valve to control this with.
I figure I will run the common port to the flapper valve actuator.
Run the normally open port to a vacuum source, likely a tee on the distributor vacuum advance. I figure this will be how its ran roughly 99% of the time.
Then run the normally closed port to atmosphere.
That way when the solenoid is deenergized the flapper valve in the air cleaner will actuate allowing in warm air, power on will close the flapper valve and allow full cold air to the engine intake.

[oil pan 4]

Well it absolutely works.
Fire it up and the engine smooths out as the exhaust manifold warms up, which happens very quickly, in about 20 seconds.
Put power on the solenoid and it opens to cold air.

Our sharp eyed readers might have noticed I did not use the Russian thermostatic air mixing valve. I needed a 2.5'' to 1.75'' reducer elbow to do a clean install, so I ordered one from frozenboost dot com.
I need that hot air on startup more than anything at the moment.

Cold air open.


Hot air flap closed.


Preheater tube attached to manifold


Vacuum solenoid.


Extra vacuum solenoid next to 15mm wrench.

Actual size.

[oil pan 4]

The thermostatic valve does work.
I have a feeling its choking the engine at higher RPM and under load, but that's ok because that encourages me to keep my foot out of it.
It can choke the engine pretty bad on start up before the thermostatic valve opens the cold air port. It takes maybe a minute for the exhaust manifold heat to start opening the thermostatic valve.

Now if I could only add a second air cleaner snorkel I would be all set.

[oil pan 4]

Here is what it looks like installed.

[oil pan 4]

I took this setup on its first little highway trip. Only about 20 miles each way.
The thermostatic valve did not choke the engine at higher RPM as I feared it might.

The warmer air has richened the cruise mixture from between 15 and 16 to 1 and brought it down to between 13 and 15 to 1.

[ExDelayed]

Neat post. I was thinking of doing something similar when I finally get my Dakota running.

[oil pan 4]

To keep the thermostatic valve made for a 1.6L engine from choking the 454 which is now an 8L engine (the old 454 went to the machine shop and is coming back as 489 cubic inches). The carburetor also has to get bigger, going from an edelbrock 650 to an edelbrock 800.
I have picked up another snorkel/flapper intake tube. The idea is to punch a hole in the existing air cleaner with my plasma cutter and weld the 2nd snorkel to the air cleaner and install a second thermostatic valve. Just a copy of the one I have and install tee fittings in the vacuum lines to control it.

The thermostatic valve just arrived from the Ukraine and the intake snorkel tube is in the mail.