It’s no secret that I like thermostats. Early on in my auto hobby, I thought it was a good idea to run a my motors as cool as possible. This is so wrong I can’t even stress how much damage it does. I could never understand why I couldn’t keep my oil clean.
Metallurgy is a funny thing. It’s amazing how much engineering and science goes into the process of casting / forging of engine parts. It’s with this understanding of the expansion and retraction of metal at different temperatures that I came to understand the correct way to run an engine. For example, take the imports and newer cars of today. Emission standards and the desire by the consumer market have driven engineering to make engine that run cleaner and last longer. Take a Honda for instance. I have one as a daily driver. Some folks may frown upon this but take note; when my girl bought this car (it’s a Civic). It had the highest percentage of domestic made parts and assembly than any other car in it’s class and price range. Anyhow, getting back to the subject of temp. If you ever worked on or spent any time around one of this small fuel miser compacts, you will note that the fan comes on like ever 40 seconds when it’s at temperature. The point is, it’s so important to keep the engine right at the correct temp. It’s also why it has a tiny radiator and warms up so quick. The idea here is that it run most efficiently at operating temperature so they want it there asap.
So let’s look at the VW type one without a thermostat. You hit the key and start it. Right away the fan is spinning. It’s cooling the top of the cylinders, even though they aren’t even warm yet. Meanwhile the bottoms are getting hot but, slower than they should as the heat is finding its way to cooler metal. So eventually the engine gets hot, but not evenly. This wears the shit out of your cylinders. I learned a lot of this from experience and also from Bob Hoover. Take a look at some of the writings he did before he died a while back. So what you end up with is an oval shaped cylinder, improper ring seating and blow-by. Wondering why your oil is coal black in 500 miles? That’s why. Shooting oil out of your breather when you get into the high revs? Blow-by due to a worn out set of rings probably early since they have been running at the wrong temp their whole short life. Plus, if you have working heater boxes in your car, the thermostat really makes a difference in windshield defrost. This is because the fast idle caused by the choke warms up the exhaust first. The thermostat is keeping the flaps closed and all of that fan air pressure is blowing that first bit of engine heat that’s building in the exhaust (heater boxes) up to you and your windshield. Yay!
Also, take into account that most VWs of today aren’t running the oil bath air cleaner. It had 2 tools built into it that help heat up more quickly; The stove pipe that scoops air from under 2 cylinder and feeds it up into the air cleaner. The 2nd part is the thermostatically controlled flap that keeps the air coming in from the stove pipe until it warms up enough and lets the flap open. Then cold air in from the “snout” of the cleaner is fed to the engine. These very in style depending on which kind of air cleaner you have. Most people don’t understand what they do and how important they are. When I was young I admit that I to replaced a few of the stock air cleaners with the “cool” chrome one. Not only does this kill your warm routine, but it also hurts performance. People will argue with this fact because they see a gain when they add it. The truth is, NOBODY ever serviced the oil bath cleaner so it’s so gummed up, it’s not working well. What the original air cleaner has is a big velocity stack built into it. This helps flow to the carb venturi. Turn one over, you’ll see. Now clean the filthy oil off of your shoe Try and find a wax filled thermo switch (see picture) that works. I have 2 of them, they both work (for now) and I have about $150 in the 2 of them. Some oil bath air cleaner units had the warm up flap that runs off a cable connected to the fan flaps. This is probably an easier setup to find and get working these days.
This brings us to dividing point. The true artisan, the guy who will find a way to clean and service the oil bath and restore it’s function. Or the latter, some guy who just slaps a chrome one on la la la down the road.
Another big problem that is so seldom addressed is manifold heat. VW themselves makes the riser run through the intake and gets it hot. On aftermarket headers the heat riser just pops right out of the exhaust on the outside of number 2 and 4 cylinders. The factory had the heat riser coming out of the number 2 cylinder and then snakes down and around and goes in the muffler right near the exhaust pipe. The factory setup uses the “push” from number 2 cylinder and the “draw” of the exit point that’s right by the tailpipe to cause a steady stream of hot air through that riser. The aftermarket setup just pulses it back and forth. The aftermarket setup provides way less heat if any at all.
Fuel only burns when it’s in vapor form. So if the intake has frost all over it and the risers aren’t too hot to touch, you’ll never be as efficient as you could be. The fuel puddles and the motor sputters sporadically and smokes. The absolute most common setup you see at shows is a really rich “wack” carb adjustment that allows a car to run ok (crappy) because it has no heat riser / plugged up heat riser or the poorly designed aftermarket 2/4 push pull attachment points.
I’ve learned the hard way that a really slow and steady idle CAN”T be achieved without decent intake heat unless you have dual carbs. The aftermarket still only offers the “pulse” setup on most exhausts. They will never change because the jigs for these systems were made a zillion years ago and that’s not going to change. It’s up to you to modify them if you really want it to work right.
So many people run duals these days that it often doesn’t matter as much as it used too. If you want to run a progressive or other center mount carb you need a lot of manifold heat. Aircooled.net actually offers the service of altering the heat riser if you want to run a progressive. They also offer an intake that has heat all the way up to the carb base. A lot of folks think that running a center mount Weber progressive is a crap setup. In all truthfulness it is one of the toughest carbs to get to work completely right. When properly setup, it is the best performing single center mount carb available. The one only issue with the weber setup is the inability to run the stock air clearer and therefore not have the benefits of the warm up. However, if you don’t run the car in cold temps and have decent intake heat, you still will get a pretty decent running vehicle.