Club 80-90 Forums

I have just had issues 3 years apart with two DG heads, both are from an older single piece bearing case. The have both failed/hairline cracked in the 90 degree lip behind the headbolt in both cases the right hand upper headbolt looking at the head on the engine. On looking at my later heads I can see that in this position the later heads have a slight curved radius of metal here instead of the 90 degree cut. I wonder if this was changed to reduce the risk of a crack developing?

My second point of interest is that the passenger side head which has recently cracked was stripped and the valves and springs etc from this were re lapped into a new head as they were in good condition . The exhaust valves had a couple of small pits in them but no big deal for LPG and three years running. The right hand head had been replaced with a second hand newer one a short time after the original engine build again using new valves from BW just like the other side. This side however cylinder two just needed relapping but the exhaust valve on cylinder one was so badly pitted I have had to change it. This head has done the same mileage roughly as the other side about 20000, I wondered if this was a heat thing? This cylinder is the furthest from the water pump? Anyone got any idea's?

I have had a cracked head on LPG before but it was not new so who knows if it had been over heated before.


early late head by Paul_Barr, on Flickr

My heads have not cracked in the combustion chambers but just under the outer head bolts on the plug side of the head. The pads where the head bolt tighten are machined into the head and on the raised side the older heads had a coarse 90 degree cut out . On the newer heads this cut is made with a small radius curve. I now have a pile of three old heads all having cracked in this position. No cracks are visible with the naked eye but as the engine runs if you clean off the pink coolant you can see coolant welling up out of the head surface in a small bead then running down and onto the floor. With dye you can just see a hairline crack differing lengths on all three but all eminating from that 90 degree cut out for the head of the head bolt. There must have been a weakness in this design causing the addition of the radiused cut on later castings. I am practising my welding of cast alloy to see If I can repair one successfully. I am using a stick welder with special rods for the vw castings.
I also have a head where the crack is between the waterway and the exhaust port wall. This one is destined for the scrap man!!

got a picture please?

itchyfeet wrote: I have had a cracked head on LPG before

Some people like to run very advanced ... hot, fast and lean. Frequently the recipe for tears before bedtime.

Ian

I had a cracked late shaped head similar to this, it was on the MV engine that I bought to rebuild, and only showed up when the rebuilt engine was running. I suspect that the engine had been stored head down with no anti freeze and cracked when frozen. Drilled a hole at both ends to stop further cracking and had it TIG welded by a local chap, and has been ok for the last 8 years. Pinkies crossed.