Follow along as I build a high performance 914 engine
First Start and Initial Tune
Sunday was the magical day... After much preparation, there was nothing left to do, but start the engine! I rolled the test stand up to the garage door:
Connected outriggers to stabilize the stand, hooked up a battery and put the fuel line into a gas can:
With my family providing a count down, I pressed "start" and the engine sprang to life!!
I kept the RPMs above 2,000 for about 20 minutes to break in the camshaft. Then, after letting it cool down, I started it up again and did some tuning adjustments.
First step: adjust the timing. I'm not really sure what it will end up being, so I set it to conservative specs to start out - 7.5° BTDC (before top dead center) at idle and 25° BTDC at 3,000 RPM. Once the engine is in the car, I'll be able to tune it on a dyno to see what's the best setting.
Second step: balance the carburetors. Do do this, it's important to disconnect the throttle linkage. This was easy for me - I just undid the cable clamping screw on the pulley of the slave carb. Using a synchronizer tool, I then adjusted the idle stop screws (the ones that control the closed position of the throttle shafts) until the air flows were the same. I then hooked my throttle linkage back up, tested it again, and then tested it at partial open throttle (to make sure the carbs remain synced through their range of motion).
Third step: set the idle mixture. Doing one cylinder at a time, I turned in the idle mixture screw until the engine developed a misfire. I then backed the screw out until the miss went away, then backed it out another 1/2 turn.
Now it's starting to sound the way a 914 engine should!
|All pictures and text copyright 2008|