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I’m finally getting my 89 Corvette running pretty well & with the new TPIS Super L98 cam & loads of repairs along the way. Initially my timing was 4 degrees retarded when I first drove her & now she’s at 7 degrees advanced & really pulls hard! My question is this, can I advance the timing & if so where might I end up at? Or does the ECM some how negate setting the timing advanced more than the recommended factory 6 degrees advance? I’ve read conflicting thoughts on this. Thanks guys
You set the distributor ignition timing with est disconnected to whatever the emissions decal on your car says. If you have had custom chip burnt and installed you set base distributor timing to whatever the tuner tells you to. If you're starting with a stock tune and using a miniram you need a chip and some tuning. Surprised tpis didn't tell you that when you bought the intake manifold from them.
The ECU extrapolates the base timing amount and adds retard or advance based on the tune. So to specifically answer your question.. you can get in Trouble advancing the timing beyond what the factory setting is. The ECU commands 36° but it actually sees 42° and the knock filter cannot pull enough timing to keep it safe, or it has to pull to much and it sets a check engine light because it's trying to do something that is not agreeing with the program. I suggest you talk to Brian Van Schoiack aka tuned performance, or Scott Hansen. Both do excellent work and have a great reputation in the tpi community.
Yes you could damage the engine by advancing it too far. If it has the factory tune it was set for 6 degrees advance. A little more won't hurt but I personally would not go over 8 or 9 degrees advance without data logging and a custom tune.
Still the stock tune in her but need to change that very soon!
I’ve installed Bosch 3 fuel injectors, the TPIS Super L98 Camshaft with new springs, a set of 1.6 full roller rockers & new timing chain set. I’m using the stock TPI setup so I ported/polished & gasket matched everything from behind the throttle body into the heads an inch or 2. I spent a bunch of time on the base & in the end it all aligned beautifully.
When I set timing I disconnected this plug;
This is what my timing was before I set it to 7 advanced;
The change in performance was truly shocking with the change in timing. I could barely believe that just the change in timing made that much of a difference!
Yes you could damage the engine by advancing it too far. If it has the factory tune it was set for 6 degrees advance. A little more won't hurt but I personally would not go over 8 or 9 degrees advance without data logging and a custom tune.
If your car tolerated 8-9° and had slightly tighter tolerance stack from the factory, has clean combustion chambers, maybe low mileage or a plethora of other things it tolerated it, and that's great. But say his car has had crap gas ran for years, has Carboned up pistons, maybe the quench is looser due to tolerance stack, maybe his timing pointer is off 1-2° advanced, yours was off 1-2° retarded. or so many things it would take three pages to list the possibilities what worked for you could be enough to destroy his engine at worst, at best cause a check engine light. So the key things you said I would like to quote and emphasize..
"without data logging and a custom tune" changing the timing advance could result in bad things period!
And it's all but a gaurantee the miniram is going to need different tip in timing, different acceleration enrichment, so it's going to be lean with the tpi tune on tip in most likely, that coupled with timing that's excessively advanced could end badly! We would do well to not suggest timing numbers for any engine other than our own. Most professional tuners will not, as car owners we would be wise to follow suite. What worked for our car is gauranteed to not be optimal for a different combo. Too many variables to just throw numbers around. The op believes, pounds out a rod bearing, or cracks a ring land because he naively believed our number was safe.. the answer is datalog and verify knock count is acceptable because each combination is different. Just saying.
Setting Optimal L98 Timing
