[Gmecm] Timing table change needed with CR increase?
davida1 at hiwaay.net
Mon Jan 29 07:50:03 CST 2007
Hey guys, I'm rebuilding a 1989 3800V6 from a LeSabre. It has the SFI
system using the 1228253 ECM.
Anyway. The engine has 370,000 miles and the intake manifold gaskets
started leaking water into #5 cylinder. So I tore it down for a rebuild.
Amazingly little wear. I would like to improve upon this motor by
installing flat-top pistons in it. The rest of the motor will repain stock.
What is a good general "rule of thumb" for changing spark timing to
prevent pinging when increasing CR? Will this be enough of a change to
necessitate spark changes? What areas of the table will need the most
reduction in advance? These are fairly highly-tuned from the factory; but it
only has 8.5:1 compression. I bet a set of flat top pistons would wake it up
and help on fuel mileage.
Any input would be GREATLY appreciated!
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