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
Adjustable Pushrod for Measuring Valve Geometry
With my engine tin ready to go and with one side of the engine mocked up, it's time to start focusing on the valve geometry. Jake Raby has an excellent article describing the process and the reasons for doing it on his website. The short version: there are a lot of variables that dictate the pushrod length (like cam base circle, cylinder shims, valve seat location, valve stem length, rocker post height, etc) - so the best solution is to accurately measure what the pushrod length should be - then make custom pushrods. To figure out what the length of the pushrod should be, I'm going to use an adjustable pushrod - this way I can change its length and measure what the valve does with a dial indicator. Here's my adjustable pushrod:
Now, this goes in our engine mockup:
And the dial indicator is set up to measure exactly how far the valve moves as the crankshaft (and camshaft) rotate:
Now, I'm already to measure, measure and measure some more. Jake recommends that this be done in a continuous 8 hour session with no interruptions... Maybe I'll get it done by the time my toddler goes to college.
