Bore Wear
Not worried about changing that thermostat? I suppose you are fully aware of the implication of running an engine that isn't up to temperature?
If you have a carby engine you would know fully well how the idle suffers, especially on startup, because the fuel isn't able to get into a gaseous state coz the manifold isn't hot enough:- that's why the choke is closed and loads of fuel is pumped in via the emulsion tube circuit in an effort to get some vapour action going.
So your cylinders aren't up to temp and you're throwing loads of liquid fuel into them. The economy isn't great, but that liquid is also giving the walls a good flush so the lubrication isn't too brilliant as a result. The oil also starts to sludge and eventually it cakes your oil screen and coats your rockers. For the sake of the argument let's say this is not a factor and just focus on the bore wear because the walls aren't up to temperature. The following table gives you an outstanding reason why faulty or even a missing thermostat is a problem.
You can make your own mind up about starting the car and letting it warm up gradually under idle or running around with the thermostat removed thinking a cool engine is a good thing.
| Water Temp °F | Wear after 60 hours (inches) | °C | mm | Increased wear factor |
| 200 | 0.0002 | 93.33 |
0.00508 |
0 |
| 180 | 0.0004 |
82.22 |
0.01016 |
2 |
| 160 | 0.0006 |
71.11 |
0.01524 |
3 |
| 140 | 0.001 |
60 |
0.0254 |
5 |
| 120 | 0.0016 |
48.88 |
0.04064 |
8 |
| 100 | 0.0022 |
37.77 |
0.05588 |
11 |
| 80 | 0.003 |
26.66 |
0.0762 |
15 |
| 60 | 0.0045 |
15.55 |
0.1143 |
22.5 |
| 40 | 0.0075 |
4.44 |
0.19685 |
38.75 |
Below 40°F the wear races away.