When to shift?

[Schyrjajew]

Hey guys. I am from Switzerland and I have a '68 Valiant 170 cui with three on the tree. (not running at the mom.)

In Switzerland about 80% of the cars have manual transmission, so I know how to shift and the position of the gears...

BUT I never drove a car with less than 4 gears.
Now I just want to ask you (because I can't wait till I can drive it myself ) when I need to switch the gear?

For example: With my 6-gear-transmission I switch from 2 to 3 with 30kmh (18 mph)

How is it with three on the tree?

Sorry about my orthographic mistakes

 

[72bluNblu]

When you hear the valves start to float, shift.

But, more seriously, you have a small engine without a ton of power. So, you'll want to shift to keep the engine in it's power range. Shift too low and you'll bog down. Rev too high and of course you can damage the engine. But the gear spreads on that 3 speed are pretty wide, so, you'll have to shift significantly higher than with a transmission that has more gears if you want to keep the engine in its power range when it drops into the next gear.

It will also depend on your rear axle gearing and tire height, which you haven't mentioned.

@AJ/FormS is the gear ratio guru, maybe he can get you some more exact info based on your set up.

 

[Schyrjajew]

When you hear the valves start to float, shift.

But, more seriously, you have a small engine without a ton of power. So, you'll want to shift to keep the engine in it's power range. Shift too low and you'll bog down. Rev too high and of course you can damage the engine. But the gear spreads on that 3 speed are pretty wide, so, you'll have to shift significantly higher than with a transmission that has more gears if you want to keep the engine in its power range when it drops into the next gear.

It will also depend on your rear axle gearing and tire height, which you haven't mentioned.

@AJ/FormS is the gear ratio guru, maybe he can get you some more exact info based on your set up.

Thanks 72bluNblu for your answer.
The Valiant was also made in Schinznach, Switzerland, and the standart engine was the 170...

I have also a 198 engine in my garage. Do you know if the power-difference is noticeable?

 

[72bluNblu]

Well, I'm not really a /6 guy. Looking at the stock specs a '68 170 made 115 hp and 155 ft/lbs of torque, where a '70 198 made 125 hp and 180 ft/lbs.

So, that's not a big difference. The hp difference isn't something you'd probably notice by the seat of you pants. The torque difference is though. It's not like it would turn the car into a rocket ship. But as they say, there's no replacement for displacement. And anything you did to a 170 to build power would make more power with a 198. It's a bigger displacement change than going from a 318 to a 340, or a 340 to a 360, and we all know how people feel about those engines.

 

[yellow rose]

The fewer the gears, the higher you have to shift above peak power.

If you are talking about just cruising around, shift it when you are comfortable.