AS41 Magnesium Alloy Case Welding the tricks

23rd June 2009
The Magnesium/Aluminium case design of the AS41 case i renown for being one of the lightest design engine cases even by today's standards. This was the brilliant invention of the VW factories in Germany who originally built the engine to power planes. The downside of this design is that the Magnesium/Aluminium alloy was a mixture that was hard to weld. The obvious risk of this being igniting the Magnesium whilst welding so that the hole part you were welding burned with a large flash eating away its form. Traditionally welding these materials takes a great deal of experience as the welder needs to be aware of the composition and must apply only enough heat to weld and not combust. It is also paramount that you have a hammer with you available to beat the crap out of the area you are welding so as to knock the burning magnesium out of the area. The downside of this is that i can leave a larger hole than you start with. Crucial to the weld is also the composition of rod that you use and traditionally the flame is better controlled by a tig welder. Most people believe wrongly you need an Aluminium rod with a Magnesium content to weld the AS41 case. The result of this I found out quite quickly was not the answer and the shop that I asked to weld the case up produced the hole filled and taped but not surprisingly the plug they had welded in did not bond to the case and was simply able to be pulled out.

The correct welding rods to weld an AS41 case are in fact Magnesium rods with a low percentage of Aluminium. The actual percentage being 8% Aluminium to 92% Magnesium. These are available from Armour supplies Ltd in Hastings, East Sussex UK .

Withe the case welded so that the main gantry was plugged I was able to get the case re taped with the 3/8" NPT tap. I used a workshop for this and had to remove all the engine main studs so that it could be mounted in their mill. you can see from the photograph that I decided to have the area made bigger so that the thread had a good fetch into the casing.

The finished plug looks stronger and more durable than the original. I am very suprised this can be done and it blows a large rasberry in the faces of everyone that says it cannot be done or to put it a better way the people that have kept this a secret from us for a long time are now all aware we all know,. I look forward to seeing a lot more cases re welded in the future.

As the answer is a vertible YES!!!!!!!!!!!!!!!!!!!!

A new 1300 dual port engine

5th June 2009
I had started to realise that with the break up of my relationship that my new 2L engine was going to be something further distant that I had planned. I was planning to have the engine in by the end of this year and with the custody fight and various other depressing events I needed to find a solution that would get the engine situation resolved as my friend had been very good to lend me his engine lump but obvuously I wanted this resolved. I managed to purchase a 1300 dual port lump that had been dry stored in a lockup for some years. Although the engine had some end float outside the allowed parameters generally it looked in good condition.

Initially I decided that the engine would need stripping and the piston rings would need replacing , but I also found that the con rod bearings and crank bearings really could do with renewing. I really had not planned for this and had decided against renewing at this time until i was placing the pistons back on to the case and pung one of the pison ring clps accidentally into the casing.

This normally would have been a disaster but to be honest I was already considering stripping the block down and decided that this was now had to happen. You can see from the diagram that the gudeon pin clip was lodged beneath the camshaft and was totally uneccessable from the oil plate. I took out the crank hsaft and camshaft and cleaned the engine parts thourougly with gink and then jet washed them off to remove any final engine residue.

The engine casing parts cleaned up fairly well and without the use of a dishwasher I was unable to get them as clean as I had with the other cases I had worked on. I couls ssee from the bearing journals that the crank had not damaged the casing and the case was in good condition. I decided whilst I had the case apart that I would full flow the oil system so that it would be able to cope with any future upgrades. This consisted off tapping the casing outlet of the oil pump for a 1/8" NPT thread and tapping the main oil gantry to provide a return a 3/8"NPT thread. The oil pump casing was quite easy to tap and this can only be done with the negin in half. The 3/8"NPT main return thread was a hole differant ball game. The thread would not take in the casing and instead just powdered up and dug a hole . This was a disaster as there was not much room in the casing to put in a case saver. I new that I would have to delve into the world of case welding something believed to be a Pyrotechnics black art.

Engine Overhaul - replacement crank case

1st October 2008.

After reeling from my engine case problems which occured when I was overhauling the original engine crankcase. I soon realised that there really was no way that the existing case could have been bored out to 94mm to accept the new barrels and pistons I had purchased. The main reason for this was that the 1300 box used adapters to hold the 8mm heads into the crankcase These adapters are know as case savers and where fitted to the later engines. These would have not allowed the cylinders to be bored out without cutting into these threads. This would therefore have not worked. Fortunately my original case had developed problems when I taped the oil gantries out to take the brass plugs. One of the 1/8NPT plugs under the fly wheel had split the case rendering it unusable. I am presuming that there was a fracture in the case prior to me cutting the thread that had spit when I used the extracter to remove the brass plug.

I managed to find a replacement crankcase on VZi from a gentleman in the other side of Brighton. Luckily the new crank case had been bored out to 94mm already and was already machined for full flow oil. The full flow oil process requires that the outlet of the oil pump be threaded and a plug screwed in and the main oil return be taped with a 3/8NPT tap. Generally speaking the new case was in good condition and had never been line bored as it was 64mm on the main bearings.

I decided that as i did not know the condition of the oil gantries that i would have to tap them. I started by removing the pressure valves. These are located on the bottom of the case at the front and back of the engine. The pressure valves and springs are covered by a screw in plug that has a large screw driver slot in its top. The easiest way to get these undone is to tap the right side of the slot with a screw driver and hammer , so using them as a punch to knock the cap undone. With the caps removed the springs can be removed giving access to the pistons. These are usually pressed tight up into the engine. I use a piece of cane that I cut down to gain the correct width to just fit into the piston. Once you have the right diameter you can knock this into the piston so that you can twist the piston out and ease the cane and piston out.

The gantry caps could then be removed from the case. I used a 1/8 drill to drill the centre of the caps and a wood screw turned into the cap until it was firm enough to allow a claw hammer to pull the screw and the cap out together. The exposed gantries could then be drilled and taped with their respective threads 1/8NPT, 1/4NPT and 3/8NPT. There are four 1/8NPT holes that need to be drilled out to 11/32". The two 1/4NPT threads can be taped straight into the gantry as the hole is already the correct size. The two 38NPT threads require the gantry hole to be drilled out to 9/16" before they can be taped. Generally speaking you need to drill the hole a bot longer than the length of your plug. I found that when taping the threads it was better to start the thread with a taper tap. I cut down a second taper tap to make a plug that was the same length of the screw plug that I was using. With the used together I was able to get the plugs to seat below the level of the casing.

Once I had taped and cleaned out the gantries I decided I would like to get the case media blasted to bring back its surface to look like new.

I also found out via a friend that as I was building a large engine I would probably be best to locate a new balanced forged crankshaft although I hadnt figured this into my budget I new that if my existing crank failed it would damage all the other components around it and so was really not worth the risk.