change up - change down or leave

[T1 Terry]

The engines can rev to 95km/hr ,or more, in 3rd so 60km/ hr is no sweat.
Too lazy at mo to work out the appropriate revs
As you noted, they are air cooled so pick revs over lugging anytime.
I sometimes have it in 4th @ 60km but any hint of a upward slope i change back to 3rd.
Less strain on engine in my view 

Thats for 1800 and 2 litre. Stock ish OD tyres.

My '74 kombi has an 1800 motor and 2 ltr gearbox. The diff gearing is a bit higher in the 2 ltr gearbox and 60km/h in 4th is for flat running and slightly down hill. 
Not only is the cooling less at low revs, so is the speed the oil pump is turning. Not so much on an issue with a newly build engine, but in a well worn engine it means less oil pressure. Lugging also destroys bearings, excessively high revs scuff rings, but the 1800 revs happily to 5,500 rpm and that takes my kombi up to 100km/h in 3rd, though I don't generally do that rpm to it unless it's been running for a few hrs and well warmed up and only so I can snatch 4th on a slight uphill climb or just as I crest a big hill to get away from the B double that will appear in the mirror on the next hill 
I'd estimate 80km/h in 3rd is well within the rev range that the engine is happy to spin at ....

T1 Terry

[merrymike]

Hi,

I have owned Mr K for many years and had his motor reconditioned (now 2.1L type 4) a year or so ago, so there is plenty of torque (its all relative of course ).   Many times when driving I find,  on a gentle hill at say 60km 4 gear means the engine is handling it ok but working hard, whereas 3rd gear means he is revving fairly high ( sorry about all the generalities)

So.......my question is .....is it ok to let the engine operate under obvious load for short distances or go for the higher revs to take the load off it and suffer the higher revs (and wear?)  My understanding is as its air cooled, labouring at low revs means less air cooling from the fan which pushes engine temp up and increases strain on engine components.

cheers

Shifting back to 3rd when going up a hill at 60 km/hr will put your revs up to where the engine would be spinning in 4th at ~90 km/hr.  So you aren't flogging the crap out of the engine by shifting down in that use case.

If you have a type 4 gearbox the 4th gear is pretty tall, 0.889, so unless you're on level road, you'll be working it pretty hard.

As a rule of thumb, if I find I'm driving up a hill in 4th and the engine can't maintain the vehicle speed, or I have my foot flat to the floor and it's "just" keeping it, I'll drop back to 3rd.  I'm happy to go up to 80km/hr in third up a hill. 

I would recommend getting a 123TUNE distributor as well - it can shift the timing on individual cylinders by a +/- a degree so your engine is a lot more balanced, quieter and smoother at higher revs.