I have an 89 LO3 auto Formula and an 88 LB9 IROC. howmuch tolernace can the chips handle as far as cam swaps before I need a new chip?
Also my friend has an 84 L69 T/A; he wants to put a 350 in it but has to retain the computer controls for emissions; will he need a new chip?


If these are dumb questions I apologize. This is one part of the cars I haven't got into yet.

 

Take a read around the forum, you'll learn a lot. Start with the stickies.

The further you go from stock, the further the tune degrades. In other words: you could put in a cam that say has 5* more duration than stock, and it'd probably run just fine, but you woudln't see any gains either (5* over a stock tiny cam is practically no gain in power, so why even bother). There are plenty of people here who think the stock tune is already off (for performance use) right from the factory, so in many cases you're already starting with a non-optimum setup and just going down hill from there.

If you want to actually see some real gains (I.E. a cam with 210* or more duration, headers, better intake, etc.) then you are squarely in the realm of needing to tune it. A bigger intake with different cam timing events and an exhaust that actually scavenges is going to require tuning on things like AE (acceleration enrichment "pump shot") to make it run right.

With THAT said - sure, people have swapped the parts and not done any tuning, and sure it will probably start and run, but you'll be leaving power/drivability/MPG on the table that's "free" for the taking.

My PERSONAL suggestion is to start with the 88 LB9. That's a 165/MAF setup, which is often discussed on here. your 89 LO3 is TBI which, although I've seen quit a bit of TBI info on here as well, I think there is probably more easily accessed/readily avaialbe info for the 165/MAF stuff.

84 L69 is a carb. It's going to have an o2 sensor and little electronic doo-dads in the carb that lean the cruise mixture out by ..well, i don't know quite how they work. I don't think anyone has done any work on this system, it's a carb. my suggestion is convert it to fuel injection, or tune it like you'd tune any other carb, i assume the thing has metering rods and such.

 

Thanks for the reply, that gives me some direction.