One more stupid question in case I'm going mad

Relief valves
Long spring at the pulley end, short spring flywheel end, yes?

Doon..... run engine for 20 minutes. Use a infra red temp reader on each head see what you get. A seriously overheating engine will start to bind and you will hear this as revs drop.

Dont have a temp reader but drive last night for welll over 20 minutes and performance was fine just temp climbing.

Weird.... Oil is critical in heat transfer in any engine. I am not understanding why you have a constantly climbing temperature when the buggy is in motion.I would only expect this with a duff cooling fan or slipping belt or knackered oil pump or defective valve not allowing oil up through the gallery to the oil cooler and back or gallery blockage. But with oil not going thro` the cooler I would expect a very rapid oil temp rise up to engine running issues

Paul
Can you confirm
Relief valves
Long spring at the pulley end, short spring flywheel end, yes?
That's how ive fitted them, clutching at straws here.

Hi Dave, yes, long spring at the pulley end and short spring at the flywheel end. Right, oil pressure and cooling!!! When you start an engine, the oil is cold and thick and the pressure is high. So the first oil relief valve opens and sends the oil down an oil passageway to by-pass the oil cooler! As the oil warms, the pressure drops, the oil relief valve then closes and lets the oil through the cooler.

So if you have too much oil pressure from HD oil relief valves springs, too larger oil pump or too thick engine oil, your engine can run hot because the oil is by-passing the oil cooler when it is up to normal engine temperature. It is the oil relief valve on the flywheel end which generally governs the over all oil pressure. So ideally, if you are running a standard oil cooler, you shouldn't go above a 26mm oil pump! Some of the after market, combined oil pump/filter units are now coming with 32mm oil pumps when advertised as 30mm. So these can cause big over heating problems unless you use thinner oils.
People building performance engines often get over heating problems because they think they need big oil pumps but they don't, unless they are running external oil coolers

Hope this helps

Thanks Rob, thats interesting.
No idea what pump is on there, the engine was built by Dan Simpson who i believe is no longer with us.
It has an external filter and an oil cooler withb an 80* thermostat

Ive refitted the original valves which have standard springs rather than the :performance " ones which were all I could get. 
Ill take it for a run when I get a chance but not too far.
I was taking it to Rustival Saturday but going in my mates Golf now.

My concern is that missing sump plug magnet, if that's lodged in a gallery. How a magnet drops out of a steel plug i don't know and there's negligible flow over the plug to pick it up so I was hoping it fell out in the oil tray when I drained it and went with the old oil.

If all else fails it will have to come to bits and inspect all the galleries

Want the job?

If your magnet has come adrift in the motor it should stick to the pick up pipe as that is the first metal it passes before the cast pump or steel gears and if it got there there would be serious damage as they try to crush it. You could put a bore scope up the tube or remove the pump cover if not already done.

That's acrelief keith. Ive had the pump apart and pushed a magnet up the intake pipe

getting hotter and hotter on a run you could try a digital thermometer to see hot spots you could have retarded timing or a slightly weak mixture at a higher rev range causing the heat, is the standard cooler clear of debris the fan sucks in and are the cooling flaps in the open position.

If you are running a standard Fan housing the flaps are open by default as long as they are free to move. If you have the original arm coupling this should have it`s spring in place and the daft coupler to rod clips free to move with the small rod like. connections

 Go back to basics......   (See if this makes sense to you).

This has always been my first "port of call" when I have suspected an oil flow issue or even a stuck exhaust valve...
Get two containers that you can place under each cylinder head/rocker cover area. Thoroughly warm up the engine so that you know, that in theory, the oil is hot enough to go through the oil cooler route. With the engine hot remove each rocker cover so that you can see both sides easily. Start the engine and let it idle. You will not get covered in oil.... maybe just a flicked bit from the rockers so have your old clothes on. Oil makes it`s last travel up the pushrods out of the little hole on the domed end. Covers vale springs rocker arms etc before falling to the lower part of head rim. Oil goes back home to the sump down the pushrod tubes. Firstly look at the rockers and springs and you should see a decent flow from the [pushrod area back down the tubes. (You will get a bit of overflow at the lower edge of the cylinder head into the containers each side but there is plenty of time to take a good look). (Bear in mind that I have never seen both sides with exactly the same oil flow. One is always a little more than the other).
As I see it when I look at things in this manner if I have a decent flow of all from all pushrod tube tops and oil going back down the pushrod tubes then the oil flow is un-interrupted through the oil galleries. If there is any sign of "no flow" from one or more pushrods then there is a blockage. Most often, but not always, in the pushrod. If there is no oil then that`s bad news but is very unlikely.
I would then argue that if the engine temp` continues to rise past a normal operating temperature then either a restricted flow or none at all is going through the oil cooler. This happens. It can be crap in the oilway to/from cooler. Can be dismantling cooler seals. Can be a cooler issue itself but if original VW no matter how old it`s rare.

A few words there but I am describing a simple thing that only takes 30 minutes at the most and it gives you an idea of wether all is well or to save much time second guessing it`s out with the engine. One other thing that I consider critical is whatever is used to determine temperature is climbing way past what it should needs to be accurate. What, in my opinion, is not is aftermarket sump sensors and gauges. Take a look at a Smiths gauge cost compared to an "ebay" chinese special. I am not being critical here but I fitted one of those aftermarket finned alloy sump attachments with the brass temp` sensor and an ebay gauge. Had these bits on a week during a summer and took them straight back off. A lot of money down the pan if you are looking for accuracy. Used a pan to heat up water alongside a known lab quality mercury thermometer and the results were useless.
Anyway Doon. I hope this quick check may help you decide if it`s engine out or not. At least it`s keeping you occupied 
Here is what my VW stuff says is typical temperature range in a type 1 engine within it`s Beetle home...  180 - 220 degrees F     82 - 104 degrees C 

Thanks both

Never thought of that rocker covers trick, great tip.

Full engine tune is never a bad thing Keith

It all started after an oil change.

Just an oil change......  I think the answer lies there. Many, many years ago I was told that the "simplest answer is usually the correct one"....

I have seen so many oil flow issues since the introduction of "silicone mastic"....  After it has been in oil for a while bits hanging about around "sealed" areas become jelly like, come away and I have seen large bits get straight through the mesh oil strainer. I think there is a good chance that something has got into an oil gallery. A potentially easy fix but you will know that will entail a strip down and crankcase galleries made accessible to an airline. If you have access to Trike even better. (No I didn`t mention that chemical it was a typo error honest  )

Builder didn't use solicone mastic, neither do I. So unlikely to be that.
Also have an external filter, I know some bypasses, but filter changed as well.
Even if that were the case id expect traces to be visible on the mesh.

I'm using Classis oil, always have.

Odd Doon.... I will be really interested to learn what the issue turns out to be.