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June 2007

Right, in May, we didn't get much done. Progress was slow, and to be honest, June hasn't been much better.

The rebuilt engine was fitted, the electrics were all connected up, and then the engine was cranked to test compression. Fingers were crossed. Disaster. The compression problem was not solved. The broken piston rings were not the cause of the low compression as will be revealed shortly. Cylinder 1 was putting out 75psi and cylinder 2 was putting out 60psi while on 3 and 4 we were still getting 125psi.

The engine had to be pulled again... along with my hair. I was so frustrated, I had no idea what the problem was, so I resorted to some technical advice on the Volkszone forums. I was given some suggestions on what to check on the heads, and to look to see if the barrels were out of round. With the engine back on the bench and stripped down, again, I checked over the head. I sprayed a little WD40 into the combustion chamber, and sure enough, it trickled out of the exhaust port. Something wasn't right with the exhaust valves. So I stripped the head, and found that both exhaust valves had burnt out, causing the valve seats to look a little suspect, and also a tiny crack had started to appear in the head. That head was scrap.

I did a bit more investigating, and out of curiosity, I took the other head off to double check things were ok over there. That head was water tight, no leaking valves. However, the top piston rings were both broken on this side of the engine too, but yet these barrels still returned good compression results. I wanted to know why the rings had failed, so inspected closer. The rings that had snapped measure 0.25mm thinner than the new replacement rings that were now fitted... I didn't know rings came in different widths!!

With a new head delivered, and some new tools to help with the building of this and future engines, I was back in the garage. The new head had to have all the valves lapped in again. With this complete, I check the volume of the combustion chambers on both heads because I wanted to check that the new head would perform the same as the original head on the other side of the engine. All 4 chambers measured 54cc's. With that figure in mind, a measured deck height of 0.035", piston diameter of 85.45mm and a stroke of 69mm, I punched the numbers into VW Speeshops engine calculator to determine what the compression ratio would be. 7.7:1 with a displacement of 1583cc or 97 cubic inches was the resulting figure. Something that I'm quite happy with for this engine.

The engine was then again rebuilt. Pistons and barrels, heads, all the tinwear etc etc. Then came the crunch time again. Time to fit it into the bug. And as sod's law would have it, it started to rain... heavily. Never mind, the engine had to go in, time was running out.

With the engine in, the electrical connections fastened back up, the engine could be cranked again to see if the right numbers could be reached on all 4 cylinders of the engine. RESULT! All 4 cylinders showed a reading of approx. 127psi of compression!

But thats it for June, as I type this I have 17 days till I race again. The exhaust and carbs need to be fitted up, and the carbs need to be tuned so we don't run as lean as I think we were before (hence the burnt valves, cracked heads and busted engine!)