what speed then?

[monkeyvanwestybike]

:lol: :lol:

 

[Trikky2]

Am pretty jealous of some of the speeds posted here!

I have a 2lt Air cooled T25 (apologies, etc ) and anything over 67 - 70mph feels to much and n fact isnt always possible! I have heard they are almost twice as heavy as a bay.

That sounds about right for a 1600 aircooled T25 or a non turbo diesel but it sounds seriously underpowered for a 2 litre (unless it has a large high top fitted).

The T25 is larger and heavier than the bay but not so much as to blunt the performance of a 2 litre down to the equivalent of a 1600. If it were mine I would investigate further.

 

[strongy]

in my opinion most of the failing and hot running engines are mostley just down to the fact its old and worn.ive driven aircooled stuff with no tin, bits missing ect and still had it run right and cool and ive driven stuff with everything there and done as it should but running hot and slow.dont get me wrong a looked after engine will make a difference,but a worn old engine is allways going to be a worn old engine.

 

[Trikky2]

a worn old engine is allways going to be a worn old engine.

This is true. Worn engines are a risk.

It seems like a contradiction - but worn engines are prone to overheating and subsequent failure.

One would think that a worn engine with loose bearings, clearances and lower compression would be less prone to overheating - but in fact the reverse is the case.

Blow by from worn rings will overheat the oil in the crankcase and pollute the oil reducing its ability to lubricate. Significant blow by can cause hot spots on the edge of the piston which erode and can even glow.

Worn valve guides give the same effect as incorrectly set valve clearances because the valve will not seat evenly. This doesn't just give poor running and low compression. The poorly seating valve is unable to properly transmit its heat to the valve seat and starts to overheat. The heat travels up the valve stem and burns the oil off the stem causing rapid wear on the guide, causing more uneven seating - a vicious circle. Edges of the valve will erode and can start to glow.

Glowing parts of the piston or valve will cause serious pre-ignition of the mixture damaging the piston, hammering the cylinder head,straining the studs etc. and causing a lot more overheating.

The poorly seating, overheating, valve will start to seat so badly that it starts to flex the valve stem, which at these temperatures will rapidly start to suffer from metal fatigue.

Because of the nature of this "vicious circle" situation, it can quickly escalate to the point where either the piston fails or the valve head breaks off the stem and gets crushed through the crown of the piston.

With the engine tucked away at the back of the van, when going at speed the poor driver often has little warning, other than a lack of power and/or some uneven running or hesitation. For the uninitiated these symptoms can be easy to miss and the first thing they notice is the bang of the engine destroying itself.

So, in summary, don't push a worn out engine too hard - or better still, don't keep running with a worn engine, rebuild it before things get really expensive.

 

[Pete B]

Trikky 2, what a pleasure to read such informative dialogue. Those years in the VW trade have produced fantastic insights for the rest of us. Listen up guys, this is a man with genuine experience with our beloved VW's. Take note of his advice. Alex too, (Jesus) knows a fair bit!!!! You can't run a bus , 1776 at that, not a 'big' one, like he does without having a good solid motor and a proper understanding of how to treat it. Jon also speaks great sense. These vehicles are from a period when a 45 to 50 mph cruising speed was the accepted norm, not the 80 mph plus we see today. Start driving at 60 mph everywhere and going hard through the gears to keep up and there will be big problems. Servicing on modern stuff is usually not less than 10,000 miles/12 months. On a bus, oil 3,000 miles max (I do 1,500) valve clearances every 3,000, plugs and points as needed. In the mean time I treat it with respect (mostly!) and so far it has got me everywhere. It is a 1600 single port, supposedly 'overhauled' before leaving the states.....
Now, onto speed/revs etc. Mr Haynes says 47/50 BHP @ 4000 rpm, along with 81.7/82 lb/ft torque @ 3000 rpm. Torque, that's what you need, bugger the BHP, torque is what pulls up hills, means not having to change down to accelerate and also means fuel economy. Max torque is max pulling power, max volumetric efficiency, max fuel economy, minimum load on engine. This is the point when cruising that it just feels 'right', light throttle, good exhaust tone, an unstressed happy engine!! On mine it does appear to work at about 3400 rpm (too high I know!) equating to an indicated 68 mph, 54 mph on Graham L's sat nav (He would have been happier going a bit faster, top bloke, stuck with me) I think this is pretty much what would have been expected in the late 60's as reasonable performance.
So chill, as Jon says, 'We are on holiday'
Just my opinion obviously. And it means getting one up from that rather scary number of posts.... :|