Even though it’s behaving like 180 out here’s my logic why it’s not. Adding some simple background for people getting into engines too.
It’s a four stroke engine.
- Intake stroke
The piston moves down the cylinder, opening the inlet valve and drawing in a fuel and air mixture.
- Compression stroke
The piston moves up the cylinder, closing the inlet valve and compressing the fuel and air mixture. Just before the piston reaches the top of its compression stroke
- Power stroke
The combustion of the fuel and air mixture creates pressure that forces the piston back down the cylinder.
- Exhaust stroke
The piston moves back up the cylinder, opening the exhaust valve and expelling the exhaust gases. The piston also applies oil during this stroke.
On an IDI, the harmonic balancer is key’d and the IP shaft is key’d. The IP gear also has a dowel. Yes there's a notch on the ip drive shaft. Cylinders 1 and 4 are companion so everytime the harmonic balancer line is at zero degrees (the first shorter nub on the timing plate) they are are TDC. If it's at TDC and the alignment dowel is at 11 o'clock it's exhaust stroke if it's at 4pm it's compression. (Unless it’s 180 out). The way you know this is to pull the passenger valve cover. The IP cover and watch the first cylinders rockers. You’ll see exhaust valve open and then close as the balancer line comes up to the TDC 0 degree mark infront of the timing plate nub. The IP dowel should be at 11 o’clock. Keep rotating and you’ll see the intake rocker open and close. Then you’re coming back up to the 0 degree on the balancer. The dowel should now by at 4pm. If that is backwards then you’re 180 out.
This is the “5 minute” way to orient an IDI and find TDC.
Some pics, I was considering writing up a quick tech article in the winter.
Here you can see the exhaust valve open as it’s coming up to 11pm and TDC
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