Follow along as I build a high performance 914 engine
- Begin tear down
- Long-block to short-block
- Split the case
- Take apart the crank assembly
- Remove the oil pressure relief valve
- Clean up the fan shroud
- Remove secondary oil relief valve
- Replace oil galley plugs
- Clean case halves
- Machine oil pressure sending unit mount
- Measure piston ring gaps
- Dry assembly (TDC & crank end-play measurements)
- Electromotive ignition sensor mounting
- New TDC mark on fan
- Case clearance for connecting rods
- Prepare the camshaft
- Crankshaft assembly and rod clearance
- Rod bearing defects
- New heads arrive!
- Rebuild the alternator for $8
- Modify engine tin
- Setting up to measure valve geometry
- Installing rocker studs
- Measuring pushrod length and valve travel
- Evaluate valve-piston clearance
- Making custom pushrods
- Lapping cylinders to heads
- Modifying windage tray
- Final crank assembly
- Short-block assembly
- Installing pistons in cylinders
- Long-block assembly
- Installing sheet metal
- Distributor drive cover & CHT sensors
- Installing exhaust manifolds
- Modifying Bursch muffler
- Installing transmission
- Rebuilding carburetors
- Fitting velocity stacks
- Building cable throttle linkage
- Making oil pressure
- First start & initial tune
- Preparing for engine installation
- Engine installation
- CHT gauge
- Throttle linkage
- First drive
- On the dyno
Pushrod Length and Valve Travel
Ready to finally measure that valve geometry? I am! I have some peace and quiet, a nice beer and everything set up:
To achieve the valve travel I wanted, the orientation of the swivel foot and to minimize spacer thickness, I decided to machine 0.060" off of the bottom of each rocker arm. Here's the setup in the mill:
And here the mill in action:
Now, with my dial indicator set up to measure the travel of each valve, I can adjust the height of the swivel foot, adjust the length of the pushrod and change the height of the rocker arm assembly by using spacers on the studs.
I want to maximize valve travel (and keep the travel as closely matched between cylinders) and make sure that the swivel foot that presses down on the valve is as close to being straight when the valve is at the half way point of its stroke. For example, my exhaust valve travel is 0.486", so at 0.243" of travel, I want the orientation of the swivel foot to look like this:
Here is a video showing a complete engine cycle with the dial indicator on the cylinder #2 intake valve. The exhaust valve opens letting the combusted gasses leave the cylinder, followed by the intake valve opening to bring in a fresh charge of fuel and air.
