Oil temps are (partly) rpm related, and when talking about high oil temps most automatically think "cool the oil", slap an oil cooler on the engine, and quite often this seems to cure the issue. This is treating the effect (or symptom), though, when one should be looking at what's causing the problem. Think of it as continually putting a cream on a rash that itches (which, don't get me wrong, is certainly beneficial) but not looking at what's causing the itch to begin with?
I know most of you guys have heard me rant on this before, but one of the causes of high oil temps (after ascertaining that the engine combo will live on street gas, all the under the engine sheet metal is there and it's tuned properly) is not enough airflow into the engine compartment. We build these things to make 2, 3, and even close to 4 times the power output of the original 1600 cc engine with no upgrade to the cooling system, stuff it into a restrictive space that is barely adequate for the 50 something horsepower stocker. The bigger engine now revs substantially higher (the fan using more air), the carbs consuming huge amounts of air (44IDF's will use 6-8 times the air a stock Solex 34-3 is capable of) and you have to wonder "where is all that air coming from? And the bigger question is "what happens when there's not enough air"?
With the varying rpm's and small loads imposed upon the engine when toodling around town, most of these cars seem to run fine, but have you noticed that when you jump on the highway the oil temps start to climb? If the car runs cooler on the highway on warmer days with the engine lid (even slightly) ajar there are a couple of ways to check on what's going on, one being the aquarium tubing test. Anchor 1 end of some aquarium air tube (10 feet is only a couple of dollars at the hardware store) to the middle of the fan shroud, and with someone in the passenger seat with the other end of the tube in a glass of water, start the car and let it idle while sitting still with the engine lid up. Note the water level in the tubing. What happens when you close the engine lid? Driving around town and out on the highway? How high does the water climb in the tube? Is there a water level difference moving with the engine lid open vs being closed? Does rpm affect the water level when on the highway? What happens when a piece of 2 or 3" flexible hose is used to direct air from under the car toward the firewall hole (I'd really love to hear the results of this one!)?
I first read about the aquarium tube test on the Samba. He eventually removed the over-the-bellhousing breastplate (you can't do a hole in the firewall because there's no space between the engine and passenger compartments in a Beetle like our cars) and found a huge improvement in the driveability in his 11 second street car during the summer months (iIrc he was from Utah). The gentleman also mounted a remote thermometer in the engine compartment and found that with the engine getting closer to the amount of air it needed, under hood temps dropped significantly and the engine kept it's tune (and made closer to optimal power) more of the time.
Time to start the morning routine- have a great day everybody (and yeah, I know, for you easterners the day is almost half over already!) Al
PS- I thought Gordon's temperature description was pretty good!
