Tech Tips – Thermistor Upgrade

A regular topic at club meetings, events, online and the occasional anxiety fueled text message, email or phone call is Corvair operating temperature and how to keep it down.

For over 60 years, Corvair engine temperature continues to remain a hot (sorry) topic among Corvair owners. There are many tips and aftermarket upgrades out there from the simple and cheap (setting timing correctly, running synthetic oil, de-flashing heads & making sure you have no debris on your engine) to the more complex and expensive (Nash Fans, EFI conversions, and H20 injection to name a few).

While gathering info for this topic, I stumbled upon an article written a few years ago by Jim Simpson in Group Corvair (Washington DC area) for their newsletter about thermistor upgrades made by Vairtrix and sold by Clarks.

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From Jim:

“Way back in 2016, I collaborated with Dale Dewald to publish a series of articles on the Corsa and Sypder cylinder head temperature gauge in the CORSA Communique. They came out in the May, June and July/August issues. These articles were based upon an investigation into the actual electrical characteristics of the Delco thermistor sensor and the gauges Chevrolet used in the Corsas and Spyders.

In these articles we showed that the stock system was marginal at best, with inaccuracies as great as 50 degrees from the actual temperature – and that was with a known good thermistor. (As the thermistors age, they are becoming increasingly erratic and new ones are unavailable.)

A year after the articles appeared, I received an email from Vairtrix. They had read the articles and were working on a solution to both the inherent design flaws of the gauges and the non-availability of the thermistor sensor. They were designing a system based upon a modern thermocouple sensor and a microprocessor to drive the stock gauges while correcting for their inaccuracies.

Vairtrix needed our raw data as a starting point for the design; I was happy to supply it. Subsequently they produced a “plug and play” system that replaces the old thermistor and drives the stock gauge. There are two versions, one each specific to the Corsa and Spyder models. These are now being sold through Clark’s Corvair Parts.”

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As it stands right now, Vairtrix and Clarks offer a thermistor upgrade for any Corvair engine (80-180hp), BUT!, the car needs to be equipped with a Spyder or Corsa dash with a working cylinder head temp gauge. Vairtrix is working on replacement gauges for Corvairs, but there is no ETA on that as of right now.

There may be workarounds like finding a Corvair stock CHT gauge and fabricating a single mount under the dash if you are concerned about a stock appearance. If you decide to try this and it works, let us know!

A google search will also show a bevy of aftermarket analog and digital CHT gauges and senders. If you decide to go this route, make sure that the gauge is rated for air-cooled engine temperature (up to 600 degrees). Clark’s also provides an aftermarket option designed specifically for Corvair applications. Most of these use a sender with a ring the goes under the spark plug.

What are some tips and tricks you use to keep your Corvair running cool? Did we miss something? Let us know in the comments.