Max cruising speed

[Bobs67vwagen]

Very informative points by all. As pointed out I think vw could make statements like "cruise and maximum speeds are 80mph", because with such a short warranty period.they designed the motor to be simple to remove and tear down. Vw then had a guaranteed future of service and parts sales. In the peak days of vw sales they had a dealership network that was very well stocked and able to quickly do engine repairs and replacements. That being said, I have had many acvws and never drove them flat out for extended periods. They were not intended to be fast cars in stock form. Where I grew up most were used as commuter cars to and from work. It was cheap transportation. In those days if you wanted speed you got a GTO or similar muscle car.

[sonoma_vw]

Easily you can stay within the user manual guidelines for cruising (that others have posted) and you can go all day, but only if all your engine tin is properly installed: no gaps, no missing parts, screws, or seals.

Idling a hot engine at a traffic light with any amount of gaps in your engine bay will soak up all the hot air from outside below the car, both from the engine itself and the hot pavement heat. Seal up all the engine bay gaps and it will drive all day without any issues.

I had a "tired" 1600d on a 1960 - the previous owner replaced all the stock metal with chromed tin, and there were massive gaps or missing sections. That car ran hot, and REALLY did not like hitting 65, but it was dependent on time of day/ weather. Put a fresh 1776 with properly sealed engine bay, and ok a temperature set oil cooling fan, and it can go nonstop 75-80...only dependent on how stable the road handling is.

[Bobs67vwagen]

I am still not convinced that you should rely on the 60 year old manuals saying you could drive these cars flat out for extended periods when you now have a 55 plus year old car with a rebuilt engine that was probably rebuilt by someone who may or may not have set engine specs to factory specs. Besides the tin being installed as designed, you have many other variables in carb jetting, fan and belt condition, timing, and condition of passages in oil cooler. I think as a general rule you probably would want to be a little more careful in your expectations that your old car could run flat out all day, unless you like rolling the dice with what could cost you an engine and considerable inconvenience. Your car may run very cool but to suggest that if the engine tin is in order on these cars that it is ok to run them flat out all day will not work for all acvws.

[KTPhil]

I think part of the history behind the "max and cruising speed are the same" goes back to the early cars and engines. VW designed the engine to be limited in power in order to increase durability, especially given the air cooling. Carburation and intake sizing limited the amount of air that could be pumped through the combustion process. This meant the car would only go so fast (especially in light of aerodynamics, too), and that balance of speed, cooling, and service life worked well. For those that drove 25 and 36 HP engines, there was no point even trying to wind it out over a certain speed. But they could cruise at that speed (full throttle) all day long.

But as power was increased to cope with modern expectations and roads, this balance began to get out of whack. Add emission related changes (limiting timing and leaning out mixtures), the stress on the engines was increased, even as HP increased to yield higher maximum speeds.

The doghouse shroud and Type 3 oil cooler were steps to mitigate this imbalance, but eventually it just couldn't be sustained as emission limits got tighter.

So today, our cars probably no longer equate maximum and cruising speed, even if professionally rebuilt and fresh. I don't recommend it. Mine seem happiest at about 3500 rpm and can drive that speed all day. But pushing it higher, I can tell they are NOT happy and will only tolerate it for so long without shortening their life and reliability.
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Current Fleet:
- '71 Fastback
- '69 Westfalia
Retired:
- '67 Beetle
- '65 Beetle (x2)
- '65 Bus
- '71 Squareback

[aquifer]

[Zundfolge1432]

[67rustavenger]

[KingAir42]

This topic is so interesting. I was going to ask this very question, but the OP beat me to it. I have been intrigued by the old vw ads about driving the cars all day long flat out! That sounds exciting, I love driving slow cars fast.

I’m pretty sure vw said the 40hp in a bug could reach a maximum and cruising speed of 72mph. I have a big bore 40hp and it will go faster than 72 flat out. I don’t drive it faster than 65 normally, but I was doing some testing that day. This will sound odd, but in a way I was disappointed that my car went faster than 72 because that meant I couldn’t drive it flat out, I would have to back off the throttle. For some reason I just really wanted to experience flat out. In fact I wanted to experience it so much that I pulled my big bore 40 out and installed 77mm pistons. I got to experience flat out all right, that engine was a turd. 0-60 in one minute, it was awful.

That was my fault though. Mukluk helped me with the problem as to why that engine was a dog shit. So now I have my spare big bore 40 installed and I’m back on the road.
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A stitch in time saves nine

[Bobs67vwagen]

I got my first bug in high school in 1968. I have been driving bugs buses and type 3s since that time. I have always thought the design was great and I have never destroyed an engine on any of those cars. If anyone interpreted my post to mean that you are a dummy if you rely on a 60 year old manual that is certainly not what I meant. I thought that a young person new to these cars should not be led to believe that because a 60 year old manual said you could drive these cars flat out all day that they should do so. There are far too many variables at play here for that to be relevant in 2025. A very experienced person who has built these engines might be able to do that, but obviously that does not apply to all owners today. My daily drivers for many years have been hondas. I very often hear people say " hondas run forever". Those of us who have worked on acvws know that a statement like that is not accurate. You may be able to run your vw flat out all day, providing EVERYTHING has been maintained and set up correctly. That is what I meant. Regards Bob

[pastellgreen]

[Cusser]