Ignition timing on a Large CID LS3

[hracing05]

Just curious what others have seen as far as total ignition advance on LS3 headed stroker (408, 415, 416, 427 etc) engines.

I am current at 22-20 final on a 416 I am working on, it seems happy and the spark plugs look good. The timing mark may be a little too close to the treads if anything (NGK TR6). Thinking about trying a 7 heat range, or backing off a couple degrees.

Forums are full of timing info for stock displacement LS3 engines. Thought I would see if I could get some info on higher displacement LS3 combos. I thought 20 was a little low, but it runs great.

If you don't care to share, please include the plugs heat range, and fuel.

The engine I am tuning is on 93 pump gas, with TR6, and about 11.7:1 Compression.

Thanks everyone!

[Ben Charles]

That’s fairly close for an ls3 head on 93 with that compression

[lukearmstrong1990]

at 11.7:1 comp on the best available pump gas I would personal be around the 20-22 degree region.

I would be cautious of knock in the transition through the mid area of the spark table as at that compression it will be much more prone to knock. It may require a fair bit less through the transitional area (approximately 0.52-0.62). It may require coming back to 24-25 through there. your data will tell you though.

I would also pay attention to peak torque RPM at WOT. it may need a degree removed over that 400-600rpm and added back in slowly with RPM.

its important to log data and ideally power/torque at WOT from relatively low spark and observe as you add it in 1 or 2 degrees at a time. If you add 2 degrees or add 1 degree at high RPM and it makes no difference to power/torque then it doesn't need to be there and should be removed

[hracing05]

Appreciate the info guys!

Assuming everything else stays the same (heads/cam/fuel/compression/etc.), would adding more displacement require less timing advance? Say, I put these heads on a 427, or even bigger, and was able to keep compression ratio identical. What about lowering displacent??? Would it require more timing???

Maybe its not that simple......Just something on my mind.

[lukearmstrong1990]

timing isn't really relative to displacement. Its relative to cylinder pressure.

cylinder pressure is dictated by so many things. air flow in and out, air temp, compression ratio, camshaft design, head design and fueling to name a few.

generally speaking more cylinder pressure, less timing.

example would be a stock engine will likely take more timing with a flowing exhaust than with a restrictive factory one. A cammed 6.0 at 10.6:1compression will likely take more timing than that same engine at 11.5:1 compression. An engine with an inlet temp of 30C will take more timing than with an inlet temp f 75C. an engine with 10psi boost will take more timing than the same engine with 20psi boost.