HOT

[Ayr Hed]

My '64 110/4-spd is running as hot as a pistol. After about 45 minutes of mixed highway and intown driving. i open the hood and the motor and all the metal surfaces are very hot to the touch and still hot after an hour of "cool" down. I searched the website for "hot" and got no results. I rebuilt the carbs a couple of months ago and it was running cool. Set the timing to 12 degrees and it ran fine ;still runs good..but gets way too hot now. I blew out the oil cooler and it was clear. The fan has a new belt and has proper tension. The dizzy holds 12 degrees. Where do I go from here? Could it be mixture is too lean or rich (I set it to specs when I rebuilt) ? ( If so how do I adjust..besides trial and error) Any advice will be appreciated

[bbodie52]

Is there any possibility that some "critter" crawled into your engine compartment and built a nest under the top shroud? You may have to remove the upper shroud to take a look. Such a nest could be hiding under there and obstructing cooling air from passing through. You should also check the exhaust damper doors to be sure they are fully opened when driving and the engine is warm. If one or both were to be jammed shut for some reason the flow or air could be restricted.

[91blaze]

Are you sure it's actually getting "too hot"? Is the overheat light coming on or have you checked the actual temp with a infrared gun? These engines do get very hot to the touch.

[Ayr Hed]

Hey Brad...no critter nests...re: the exhaust damper doors. are these the flapper under the oil cooler and the flapper on the opposite side of the engine ? If so, with spring tension holding the flap in the up position, is this open or closed ?

Hey Blaze...no light..re: the infrared gun..what is considered a safe max temp ?

[91blaze]

At the heads 250-350 is about normal after driving, although this may vary greatly depending on the outside temps and condition of the engine. Overheat light comes on at 500 (or 450 if you somehow get the wrong sender like I did). If you have access to an infrared gun, go for a 10 minute or so drive and get the head temps by opening the damper door on the right side and aiming where the temp sender is. As for the doors, they are closed (up) when cool, then the bellows expand with heat to open the doors. If those are not functioning correctly you will run hot.

[bbodie52]

Here is a somewhat extreme example of a critter nest on a Corvair engine. As you can see this would have some negative impact on engine cooling, as the air flowing past the cooling fins on the heads and cylinder barrels is limited by severe critter intrusion. In this picture the oil cooler is also blocked...



The thermostat-controlled air control doors are fully closed when the engine is cold, and gradually open as the engine warms up. They are there to allow the engine to warm to normal operating temperature quickly. Each thermostat bellows opens fully if it leaks and fails, so it would be unusual for anything to cause the doors to stick shut. You should be able to push on the bottom of each door when it is closed and cause it to open manually against the spring pressure of the cold bellows thermostat.

The door assembly and thermostat is depicted on the Clark's Corvair Parts catalog page shown below...

http://www.corvair.com/user-cgi/catalog ... w_page=106

Here is a comparison of a normal (lower) and a failed (upper) Corvair thermostat:

[terribleted]

Verify that the thermostat doors are adjusted correctly and manually open them to ensure they are not binding (sheet metal damage and bad door pivot bushings can cause them to bind). They should be adjusted so they just barely close when the car is cold.

[Ayr Hed]

Hey Brad...All works as it is supposed to. Went for a drive today..temp normal. The last few days the temp has been in high 80s..today much cooler, about 72...can this much difference in ambient temp cause the motor to run a WHOLE LOT hotter ?

[bbodie52]

The ambient temperature certainly has some impact, but I remember crossing the southern California desert (near Needles, California) in mid-summer during the day with temperatures around 110° or more. The car was fully loaded with a family of four and all of our luggage (140 hp Corsa). I tried to make a phone call at a payphone, but the handset was so hot I couldn't hold on to it! In spite of this, the Corsa never overheated and did well on our three-day cross country marathon from Atlanta, Georgia to Thousand Oaks, California. The family was overheated — The Corvair was not!

[miniman82]

'Overheated' and 'hot' are 2 different things, Brad.

Outside temps can have a huge impact on how the engine runs, especially if it's on the verge of not being tuned right to start off with (or about 1000 other factors). Corvair engines are cooled by air so if the incoming air is already hot, you're not going to transfer as much engine heat into it. Result? Engine runs as if it's sluggish, or possibly feels down a cylinder. If you push it, it may ping at you at any throttle setting above 1/2 way depending on how good the fuel is and what the actual temps are outside. On my car ('66 180 turbo) I found that once it got much past 87*F outside, any type of spirited driving was off limits. All it would do is detonate, and head temps get pretty out of control. My advice? If you must drive in weather that hot, put an egg under the gas pedal unless you really know what you're doing. Contrary to popular belief, you DON'T have to be at wide open throttle to melt an air cooled engine when detonation occurs. All it takes is ping and time, and you get 6 melted pistons for seemingly no reason.

I would learn what detonation sounds like now, so you can train your right foot to avoid it.


On the flip side, air cooled engines (especially the turbo ones) LOVE cold weather. While in the summer I sometimes had to drive cautiously to avoid ping, when it dropped below 65 during the fall I found that I could add a lot of timing back in and stand on the gas in every gear and never worry about it. Boost through all 4 gears at every light was not a problem. Engine would never get too hot no matter how hard I beat on it, in fact the harder I pushed it the better it seemed to run!

So yes, OAT's do have an impact and it may be more than you think. Less so with N/A engines, but the effect is the same. Hot air is less dense, so it makes less power. Hot air also makes the engine run hotter, all other things being equal. Learn what your engines 'norms' are, and when you notice it's protesting because it's hot out just go easy on it. These engines are very durable, but no matter how strong it is nothing will last if you ask it to do something it doesn't want to/wasn't designed to do...

[azdave]

Here's some more info since we are discussing driving Vairs in high ambient heat.

It was 92 degrees at 5 am this morning when I drove my pure stock 65 Corsa to work on the freeway. It's a half mile to the freeway at 45 MPH and then I drive a constant 70 MPH for 9.8 miles and the head temp indicated by the OEM gauge was right at 400F. I have no reason to belive the gauge is not fairly accurate.
When I exit the freeway it does NOT ping as long as I don't accelerate hard enough to engage the secondaries. The ping I hear once the secondaries open up is slight but I do back off of course. After the freeway it's a 1/4 mile to my work at 30 MPH and the temps drop to 350 by the time I park.

I did a 20-mile freeway round trip today at lunch time. It was 106 degrees. Temps at freeway speeds never exceeded 425F per the gauge and when cruising mostly at 60-65 MPH due to traffic the reading was just a tick over 400F. This is with full lower shrouds and properly working thermostat bellows in place.

[Ayr Hed]

overheat problem solved...after blowing out oil cooler..I reinstalled the cover plate upside down restricting airflow..stuped mistake.