Harley-Davidson VL Cylinder & Head Prep

Preparing the cylinders and heads on a Harley-Davidson VL engine is one of those unglamorous but important workshop jobs that has to happen before machining and final assembly. This round of prep focused on removing old paint, cleaning the cooling fins, handling minor head-fin damage, and getting the parts ready for refinishing. For the full build sequence, see the VL Tech archive, the related VL engine case prep, and the VL transmission prep.

Harley-Davidson VL cylinders before cleaning with old paint packed into the cooling fins — Harley-Davidson VL cylinders before cleaning, with old high-temperature paint still packed into the cooling fins.

Cylinder Cleaning Before Machine Work

If you guessed that head and cylinder prep meant more time at the blast cabinet, then give yourself a gold star! I lucked out and got a pair of cylinders that were in great condition with no broken fins and only bored out to .005" and .010". They will be bored and fitted with .020" over-sized pistons by the machine shop, but before being sent off they needed to be cleaned and repainted. This was straightforward, but also extremely time consuming. Getting all the old hi-temp paint out of the cooling fins was a tedious process. I used the same blasting media as before, a fine grit aluminum oxide, slowly working over the fins from different angles.

Head Condition and Fin Repair

My heads were not as pristine as the cylinders and required a more aggressive approach. It is common for head fins to be broken on flathead engines due to improper tools being used to remove the head bolts. A good wrench slip, on a head bolt, has snapped off many a cooling fin. Replacement fins can be welded in place and if you want to go that route, I'd recommend sending them to Faber Cycle for a professional repair.

Damaged Harley-Davidson VL flathead cooling fins before cleanup — The VL heads had the kind of broken and rough cooling fins often found on old flathead engines.

Close-up of damaged cooling fins on a Harley-Davidson VL flathead head — A closer look at the head-fin damage before smoothing the rough edges.

Since the fin damage on my heads was relatively minor, I decided to just use a die grinder to smooth out the rough edges. Once they are painted black, everything should blend together visually.

Smoothing minor Harley-Davidson VL head fin damage with a die grinder — Minor fin damage was cleaned up with a die grinder instead of welding in replacement fins.

Harley-Davidson VL head fins smoothed and ready for blasting — The fin edges after smoothing, ready to go through the blast cabinet.

Blasting and Priming

Next the heads went through the blast cabinet to clean off all the old paint and rust. Once complete, all the parts were sprayed with an aircraft primer.

Harley-Davidson VL heads after blasting and aircraft primer — After blasting, the heads and related parts were coated with aircraft primer.

The results look more like what you'd expect for WLA parts, but they will be top coated black before installation.