Timing help

[d510addict]

I am installing a rebuilt L20b tomorrow into my truck and I need some suggestions on timing. It will be running a 32/36 copy with an A87 open chamber head that has been shaved down some so compression should be near what a closed chamber c/r is. The motor has been bored .030 over and it supposedly has larger than stock valves. When I installed the timing kit I set the sprocket on the #2 notch (I believe that is what Hainz set his at in his videos. I'm not sure if having an EI Dizzy on there will affect my timing but I'd thought I should mention it.

 

My question is what would be an ideal timing to shoot for when tuning this thing? Or does anyone have a suggestion on material I can read through? I honostly do not know how the modest mods to this motor will affect how it will need to be timed so I am not sure where to start.

 

Thank you

 

~Derick

[datzenmike]

Derick there is no magic timing number you can use. If you had a stock motor then 12 degrees would be an excellent starting point. A motor is most efficient at turning heat into motion when the timing is advanced as far ahead as you can and yet low enough that it does not ping under heavy load. Some of the things that will affect your timing advance are:

 

Altitude above sea level... higher altitude needs more advance.

Compression ratio... higher compression needs less advance.

Engine temp... hotter needs less advance

Ambient air temp....hotter needs less advance

Spark plug heat range....hotter needs less advance

Octane rating of the gas... higher octane allows more advance

Air/fuel ratio... richer allows more advance.

 

Start at 12 degrees and expect to lower it slightly if it pings. (seems to me that a milled head and 0.030 over pistons will up the compression slightly) You will have to find the 'sweet spot' where it runs best for you. I loosen the distributor hold down bolt (slightly) so that with some effort, you can jump out and twist the dizzy clockwise to advance or counter clockwise to retard when driving in the real world. After a few days or a week of driving if you haven't made any adjustment, tighten the bolt down and consider it timed.

[d510addict]

Awesome D Mike!

 

This thing should go in pretty quickly in the morning I hope to make it in time for Blue Lake.