Thread: Ignition Timing - Thor RV8

Buy a degree wheel and find TDC via no.1 plug hole, attach degree wheel accurately with a suitable pointer, then fire it up.

CROW CAMS CAMSHAFT 8" DIAMETER DEGREE WHEEL | eBay

Thanks - unfortunately it is not easy to exactly find TDC through the sparkplug hole with the engine in place etc. I was hoping that there might be another method.

When the engine was out I set up marks and a pointer through a laborious process through the sparkplug hole but with the engine running on EDIS in default mode where it runs at 10 degrees BTDC the timing light shows a different reading - so not sure whether my marks are wrong or EDIS has an issue.

Hence I would like to check the timing with another method if possible without having to pull things apart.

Cheers

Garry

Some years ago I bought a TDC finder and a top quality timing light off a forum member here. The TDC finder consists of a plug hole adaptor and a metre or so of clear hose that you could rig as a U-tube manometer. This made TDC finding extremely accurate. It should be easy to make one out of an old spark plug.

If access to the front of the engine is difficult perhaps you could drill a hole in the bell housing and mark the flywheel instead. I'm assuming you're using a Thor flywheel so that should have some relationship to TDC you could discover.

Originally Posted by bee utey

If access to the front of the engine is difficult perhaps you could drill a hole in the bell housing and mark the flywheel instead. I'm assuming you're using a Thor flywheel so that should have some relationship to TDC you could discover.

I used a process that measures the mid points of stroke rather than TDC (which is almost impossible to measure directly as there is little movement in the piston at TDC vs movement of the crank) to set it up in the first place and repeated the process about 5 times and always got the same answer so was happy with my marks until I ran the engine on Edis on default mode and got a different answer - was about 5 degrees different - and the engine runs fine on the set timing even under load and up to 3500rpm so its not too far out if it is at all. I could go through that process all again but it is hard to get at number 1 spark plug hole and do the adjustments on the measuring device as body work is in the way - bad enough changing the spark plug.

I am using a 3.5 flywheel so no timing marks on it.

If there is not other way in double check, when it comes time to finally set up the engine I will disconnect the knock sensors and adjust the timing so it just starts to knock and then back off until it goes away and mark the harmonic balancer at that position - and recheck for knocking. if OK turn the knock sensors back on and let the ECU manage it from there.

Cheers

Garry

The water based TDC checker is extremely accurate due to the large ratio of piston area to hose cross section.

I would ASSUME the ECM would manage the timing once running, I can get an idle reading from OBD2 if that helps?