The SII is a great motor compared to the 3.8L in the 86-87. The Heads on the 86-87 were barely a step up from the Heads Jeep sold back to Buick in the 1970’s. The ‘89 TTA heads were even a huge step up from the 86-87 heads. Turbocharging/intercooling made all the difference. SII heads start off on a whole other level.
If Buick stuck with RWD and turbocharging, by ‘96-97 they would have had a legit Corvette killing, 380-400 HP V6 on 93 octane. I’m sure one of the reasons they supercharged the FWD cars instead of Turbocharging was the carnage that would have come from Front Wheel drive cars running 125mph in the 1/4 mile with only race gas and mild tweaks.
Before I ported the heads/cammed my ‘86, it ran mid 11’s @ 118 in the 1/4 mile but couldn’t rev above 5,200 RPM, because the heads were so terrible.
SII heads start off on a whole other level.
Now that you mention it I recall guys who work those heads saying they’re pretty open to begin with and that it’s not long before you’re in the water jacket. I suspeCT that headers and a custom intake on an otherwise stock series 2 would wake it up more than is the case with most engines. Even with a stock intake and exhaust you can hear the flow thRu the heads.