Technically, once a previously used VW air-cooled engine block is deemed to be crack-free and adequate to be rebuilt, and if the bearing saddles and thrust are sound and not in need of further machining such as an align bore, the block can be rebuilt as-is and should be sound for quite some time.
However, one thing I’ve learned from all of my research and reading is that there is “cleaning a block” and then there is “CLEANING A BLOCK“. A real thorough cleaning cannot be done by just a degreasing bath, a soapy wash, and then compressed air. Many engine builders recommend the removal of the block’s oil gallery plugs, tapping them to be replugged, and then a deep cleaning of the various oil passages with appropriate tools and solvents prior to the plugs being installed.
My AH Engine – The Recent Past
The AH engine I removed out of the original 74 Super Beetle project is a prime example of an engine that more than likely needs the oil gallery passages properly cleaned.
After I purchased the car, It became readily apparent that it had not been maintained well at all. From the poor body and chassis repairs I uncovered, as well as the lack of brake maintenance, one could tell little was done other than hiding major rust and slapping paint on it. However, the real issues of the engine and previous lack of proper maintenance, especially regular oil changes, became a noticeable problem once I started tuning up the car.
The first oil change was just plain awful.
I knew it was dark when I inspected the car but I had no idea that it had not been changed in upwards of at least 5000 or so miles. When I finally drained the sump, the oil was jet black and syrupy. Now I’m not talking about the used engine oil I see in my modern Subaru Forester. That oil can get dark after a thousand or so miles but still remains translucent. The oil coming out of the 74 was like Hersey’s chocolate syrup when it came out. And I’m not talking cold oil here. This was at engine operating temperature!
Over a 4 day period, I performed upwards of 6 complete oil changes, using a variety of bottled products sold as oil system cleaners, as well as my son’s favorite Sea Foam, trying to get the oil to come clean. With each subsequent change and driving the car for a while with the oil + cleaning additive going through the system, it kept coming out cleaner and cleaner.
Of course, complicating matters was that this car did not have an oil sump plate with a drain plug in it, so I basically had to do a total messy oil change with multiple gasket sets each and every time. I ended up transferring a drain plate magnet I had put on Murbella to the 74 in the hopes it would draw any metal particulates to the bottom as the cleaning products thinned out any deposits.
Thankfully, I never came across any metal in the oil so that was at least one positive (on what would amount to be a major mistake purchase) on this car.
I felt confident after the draining of the 6th oil change that I had gotten out as much crud and sediment as I was going to get out and I put in my usual Castrol GTX 20W-50 that I typically run.
When I did a tune up a few days later I found out how the lack of previous owner oil changes had further impacted the engine.
I went to replace the spark plugs and spark plug wires and when I popped the valve covers off to check on the rocker arm adjustments I got one hell of an unexpected surprise.
The entire rocker arm assemblies on both heads were coated with solid deposits of what appeared to be sediment encrusted oil. While my cleaning agents had no doubt made some dent in cleaning these, on the whole, these deposits were solidly caked on to the metal and aluminum
I attempted to adjust the valves and could not even turn the screws or nuts. I opted to leave these as-is as the car was running ok, just idling kind of high.
When I started on the brake work later in February 2018, I also attempted to do a valve adjustment again and ended up just pulling the rocker arms off and spending a few days soaking them in mineral spirits and scrubbing them up. Even after all of that I could not get the adjustment screws to budge and resorted to using my torch to heat them up to almost glowing to finally break them free.
I eventually did get all adjusters fully functioning again and got the rocker arms back on the engine.
However, as you can see above, the sediments and deposits that caked up the arms and the insides of the valve covers was pretty intense. I could not get it off with the heads still on the car.
When I dropped the engine and split the case, the true extent of the oil degradation that my six oil changes did not free up became apparent.
Both sump sides were caked in a black tar-like oil deposits that barely scraped off. When exposed to some mineral spirits, it started to break down and became somewhat liquid and oozed the like the chocolate syrup of the original oil change in September of 2017. Everything below the camshaft was jet black.
Those passages along the slit of the case that allowed oil to drip back down into the sump were also filled with tar-like debris.
Soaking the case sides in a mineral spirit bath did not fee up all of these deposits. I scrubbed and scrubbed and finally, most of them came clean when I took the case to the car wash and blasted it with the extremely hot high pressure soapy water.
Knowing what I had previously seen, and knowing what I was uncovering as I split and cleaned the case, I started really researching on the best way to clean and prep a case for rebuilding. What started as an exercise in how to “full flow filter an engine” became a plan to make sure any remaining oil deposit crud was removed from every possible nook and cranny in the case.
NOTE: I could never get a straight answer from any question I posed to people in the VW community if I should be worried about the unknowns of the this case’s lack of maintenance. However, let’s face it, for an engine that uses a the removal of heat from its oil system to partially cool the whole system, not having the oil properly and freely flowing cannot be a good thing. I decided to just break down and do what it would take to properly clean and prepare an almost 46 year old engine block for reuse.