Joined: Aug 2017 Posts: 422 Threads: 89
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Location: CALGARY AB CANADA
Two questions:
1) On a standard 1929 engine in stock configuration what would the red line or maximum RPM limit be?
2) We are experiencing temperatures down around the Minus 30s Celsius. How well would a '29 seven cope with this if one was drive in it?
Observations, suggestions and opinions invited.
Thanks, Stephen
(in the frozen Great White North where the temperature warmed up to minus 20 today !)
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Location: Auckland, NZ
The sports engines run at sustained rpm with reasonable life with original cranks, esp later thick ones. But forces increase as the square of revs, and a modest increase has a huge effect on fatigue life, so consideration of crank life largely determines excesses, esp if car has original thin crank. In stock non sport cars, valve bounce limits revs to somewhere around 4,500, over 60 mph even with the lower geared post 1932 cars. In their day most owners of 1929 thin crank cars would only reach 3,000 when in 2nd (26mph) most now run the later cranks and, if their ears can stand it, routinely hold 30 mph, about 3,500 (about the same rpm as 4speed cars in 3rd, corresponding about 55 in top for those models, above normal top speed)
The temps would seem to be a rare example of an overwhelming case for a thin multigrade! Car could/should be run with the fanbelt removed and radiator blanked off. (My car had a tiny hole in the radiator cap so boiling could be judged!) I guess starting would be the hard part but with a second person and crank not impossible. Where does antifreeze protection end?
Joined: Aug 2017 Posts: 3,392 Threads: 106
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Location: Darkest Bedfordshire
Pretty much what Bob said.
A standard, unmodified 1929 engine with original crank probably won't go much over 4500 rpm without valve bounce and that would be a prudent place to stop accelerating. For a tuned engine with a sound original crank 6000 rpm was generally considered the limit; but those cranks are 90 years old now...
If you want to drive at -30C, the car is likely to cope with it better than the driver! Of course you will want anti-freeze in the radiator, unless you drain down as soon as the engine is stopped.
The main risk is oil flow from start-up and you need a multigrade engine oil grade which is thin enough to circulate well at those temperatures - forget about straight 30's and 40's. Give it a good, slow, gentle warm up before going out on the road. I'm not a fan of radiator muffs, but at that temp it may be worth considering; or slip the fan belt off. People often don't realise that coolant temperature and sump temperature are two entirely different things - your radiator may well be warm in half a mile but the sump oil is still frozen treacle. If this was a regular thing it might be worth considering ways to gently pre-warm the sump.
Keep in mind Austin Sevens don't have ideal brake distribution. It's possible you might lock up the rear wheels on ice and spin the car. Having said that, I've always found mine enjoyable to drive in snow.
If there is salt or other de-icing material on the road wash it off after using the car.
And wear some warm gloves!
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Location: Scottish Borders
I've been contemplating using a multigrade such as 10/30 in normal use.
With thermo-syphon and no thermostat I doubt the engine would ever get up to working temperature at 30 below.
Split braking is fun on ice:
Apply handbrake, front wheels lock.
Steering to full lock, car continues straight ahead.
Simultaneously release handbrake and apply footbrake.
Car stops moving forward and spins round and round.
Hours of fun in the ice covered Law Department car park at Dundee University in the 60s.
Jim
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I can at least confirm that 20W50 works fine in my engine, though it is a slightly modified (pressure fed) engine...
I did some measuring last autumn and found that at 10 degrees ambient it took an hour for my 6 pint sump to reach 65 degrees © or so, and it never got any higher. This is not really hot enough.
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I was out in -27c temperatures last night. I can confirm, as suggested, the car would have almost certainly fared better than the driver in such conditions...
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Location: Wellington, NZ
I remember visiting an uncle in Calgary once and seeing the cars with block heaters and connectors so you could plug them in to keep them warm.
I think driving a car out in in -30 air would be fine if the engine is warm. Colder, denser air so it probably goes better. But the amount of damage being done if the car itself was at that temp and you tried to start it must be bad. What happens to the clearance in an engine that cold? Does everything tighten up? Combine that with thick oil and you'll get more metal to metal contact and wear.
Simon
