I have finally managed to get some free time in the garage and thought I would set about my engine rebuild. The bottom end I got from Farmer Rob last summer was indeed in very good condition, but for the sake of a few nuts an bolts, I thought I would tear it down anyway for a proper look inside. Annoyingly, I have lost the pictures I took as I went along so you now see it here on my engine cradle reassembled.





I have been deliberating for a while which direction to go with this, and have decided to build myself a completely standard block, but to get it as close to a new spec engine as I can for reliability and longevity. The knackered engine currently in the Buggy needs so much work, that I may well go a bit mad with it and build something a bit lively, but for the moment, I just want something that will not let me down this year.

Great Dave. The more buggys that have working reliable engines the better for people like me and Dave C.....

I assume you are fitting a toe bar.

I`m in 2 minds whether to refit the tow bar as the trailer tent has now been sold - I guess it depends on what I will be doing with the Exhaust, as have a few new plans for that too.

Come on, you need somewhere to store the old tennis ball !

Quote from: Hugh on January 14, 2017, 05:49:10 PM
Come on, you need somewhere to store the old tennis ball !

  You are right - Ok, it gets refitted 

My plans were to re-use the old cylinder heads on the new engine, but to give them a quick once over before I did.

I removed the left hand head and was confronted with a very sooty and carbonised chamber, which is hardly surprising really, given how bad my carbs have been running and that I had just thrown on another set without even setting them up, just to get me on the road. Still, all that carbon has got to be removed and cleaned up. In the old days, it was known as De-Coking, but most youngsters (and Halfords staff) have never heard of that term.





There are various chemicals you can use to remove the carbon deposits, but I used a small Dremel with a wire brush attachment to clean it all up, being careful not to go too heavy around the edges where the cylinder head gasket ring would go. Unlike Beetle heads, these T25 ones are not prone to cracks, but its still worth having a close inspection just in case.

One of the jobs I do want to do though is to check the valve seats, especially as its such a simple job to do. First of all, the valves need to be removed using a spring compressor. That can be problem number one, as most of the compressors on the market these days do not seem to have the right shape end on them for the VW heads. Luckily, I have an old school tool that has an angled head on it allowing it to be used to compress a spring into a recessed hole, whereas most of the modern ones just foul the sides of the head.





The tool is nothing more than a big "G-Clamp" and the other end is pushing against the centre of the valve inside the chamber. Tightening it up allows us to compress the valve springs so that the 2 split collets that retain the valve can then be removed. Once these have been removed, the clamp can be undone and the valve should just drop out.





The valve seats are critical for maintaining compression and the smooth running of the engine. I had no reason to suspect that there was anything untoward here, but I thought that I should re lap the valve seats whilst I had a chance to. What you are doing here is ensuring that there is a really good seal when the valve is closed and this is done by grinding the valve and seat together to make sure that they are a perfect fit. There are various grades of grinding compounds available, but as I was just giving them a light going over, I opted for a fine paste.





The valve seat and underside of the valve edges are lightly smeared with grinding paste and you then use your lapping tool to rotate the valve. Its worth buying a new lapping tool before you start, even if you have several in the back of the garage somewhere, as the rubber suckers on the end do perish and you only find this out once you start. Yeah, I found out the hard way too, hence the new tool shown in the picture. The idea is to spin the valve one way and then the other and if you think along the lines of rubbing two sticks of wood together to make a fire, you get the idea of what is involved. Lift the valve every few goes just to allow the paste to settle, and then start over. When you first start it sounds really gritty, and within a few moments the sound smooths out.





It doesn`t take long to do each one, and the engine will certainly benefit from it. You can see the ring on the valve and the valve seat that has now been lapped, and they look clean and of uniform shape. Unlike the face of one of the combustion chambers, where you can see from the indentations that something has been rattling about in there at some point in its life, and probably a nut or washer that previously got dropped down the inlet manifold during reassembly. The top of the piston is dent free though, so its obviously something that happened when the head was on a previous engine.





Head reassembled, cylinder head gaskets in place, and looks a damned sight better than when I started. I have also given the head a coating of engine paint because the cooling fins can get very oxidised and furry behind the tinware, and the coating of paint does seem to slow this process down a bit which in theory should mean they will be a little more efficient.





I just hope the other side goes as smoothly

Great explanation there and hopefully when all this is done things will be a lot better   

Peter

Nice work with the lapping Dave.  Looking at the pictures I think something may have spent some time bouncing around in the right pot?

A few weeks ago, a big box arrived from VW Heritage containing a brand new set of Mahle Barrels and Pistons. Its always worth popping the pistons out of the barrels for a close inspection, just to make sure that there are no damaged rings or bits of debris in there from the production process.

I knew that the top two rings were the compression ones, and that it is important that the gaps in any of the rings are rotated to be as far away from each other as possible, and I also knew that the lower ones are the oil rings. Until watching an engine build DVD kindly lent to me by MickyB I had no idea what the significance of the green and red colours were though, although I have seen them before. Turns out that these colours are printed in such a way that if the oil rings have been badly assembled, then they will overlap and only one colour will be seen. As long as you can see both colours, then all is well.





Unlike Beetle Cylinders, it is advised to only fit these pistons in from the top, because only the top edge of the barrel is flat, whereas the bottom has got a few cut outs that are used for aligning the Gudgeon Pin. If you try to insert the piston from underneath, then chances are that the rings will catch on the cut out sections and break. As you can see here, the rings stick out quite a bit and need to be compressed to get them into the barrel. If you are doing this bit properly, then it is really really messy, as you will have given everything a really good coating of engine oil for lubrication.





The Piston Ring Compression tools can sometimes be quite complicated and expensive, and those of you that are careful can usually squeeze the rings into the bores one by one using nothing more than the ends of your fingers. Its not ideal, but I have done it very successfully that way for many years. However, Machine7 do a very basic tool for under a tenner, and its worth investing in one of these if you are undertaking this sort of job.





The tool is really simple to use. You clamp it tightly around the piston rings with a pair of pliers, and then give the top of the piston a very gentle tap on the top and the piston will drop into the cylinder.





I`ll stick these to one side now until I am ready to fit them onto the engine.

Pretty sure I have a 1970 vintage ring compressor in the garage if you need a loan
Used it on my 105e and works a treat as it is quite wide so aligns everything well

The pistons are fitted to the Connecting rods in the engine by a big bit of metal called a Gudgeon Pin, or Wrist Pin if you are in the USA. I have turned the barrels upside down and pushed the piston through just enough that the pin can be slid over to one side. You need to be careful doing this as if the piston moves too far, the rings will be exposed and you will have to take it all apart and go back a few steps.





Assembly is made much easier if you fit one of the small circlips whilst its still on the bench. Fitting the other one when attached to the engine is hard enough, so you may as well make life a little easier for yourself. What you then have to do is guide the barrel down the four studs whilst trying to blindly align the Gudgeon Pin through the connecting rod of the engine, slide it home and then refit the other circlip. Sounds easy enough, but everything is an EXACT fit, meaning that nothing moves or slides as easily as you would like it to.





The gaskets are fitted to the cylinder base, and sealed with a layer or Permatex. Its the first time I`ve used this stuff, and have to say that I am quite impressed so far. I guess time will tell when the oil starts spewing out everywhere, but when applied with the brush its far less messy than the tubes of Hylomar that I am used to.





One of the top tips I picked up from watching that engine build DVD was to make sure that you fit No:4 cylinder first. The reason is because of the limited access on one side due to the oil filter mounts that stick out, and if you fit the other cylinder first, then you have no room to play with the gudgeon pin. This does also mean that you have to think ahead as to which barrel is going where and fit the circlip in the correct side for assembly. There is also the correct orientation of the piston to consider too, but I`ll show you that one in a minute.





This is one of the easier ones to fit. Whilst supporting the weight of the barrel and piston, you have to guide the gudgeon pin through the connecting rod hole, which will be a very tight fit, and this is done whilst trying to line up the four long studs through the holes in the cylinders. Its a bit of a faff, but if you take your time, its not actually that hard to do.





I mentioned earlier about the orientation of the pistons. If you have a look at the top of them, you will see a small arrow that has been stamped into the crown. It is very important that the arrow points towards the flywheel, as this is how the pistons have been designed to operate.





Cylinder head can now be fitted making sure that the nuts are tightened in the right sequence and to the correct torque.

Again, another brilliant write up with photos and well explained, I'm going to have bookmark all this
for future reference 

Peter

Cheers Peter, and feel free to use anything on here that may be of use over on your site too   

Thank You, I shall, as I have been having ideas lately 

The photos are so clear and the thread is a great reference point at which to start 

Enjoying reading this Dave. Hopefully I don't have a rebuild on the horizon though!