Not to be dis-respectful, but it appears no one in this thread has built and run a 4.1 in a GN?
My first one was about 15 years ago and was a reliable low 10 sec. ride with MANY passes. Nothing "exotic" like todays builds, as it had a stock crank and rods with Champion alum heads.
I did blow a head gasket once when the boost spiked, but no cracked or split block?
I then built the first TA alum block 4.1 and sold the complete production 4.1 engine to an owner in Cali. After a few more years I heard from the third owner who was still running the crap out of it!
I have build many production 4.1's since then, a couple for myself and lots for customers. No broken blocks or cracked decks so far.
A typical 4.1 build does not cost any more than a comparable 3.8 build, as all our builds use custom forged pistons made to our specs. Why would anyone put anything but a good forged piston in a $8-10K performance build?
Unless the customer insists, we do not install a girdle, but do put in the 2 steel center caps. The availability of forged cranks is the best thing ever to replace the weak cast crank, and give us needed reliability into the 9's, or 650-700 HP.
For the same engine cost and comparable overall build, I will take on any street GN with a 3.8!
The low end torque and acceleration is awesome.
With my personal experience running a 4.1 at the track, it will easily run into the 9's and 130 MPH+ with 16 PSI in a street driven TR.
I presently have two 4.1 builds in process, with a just finished one on the stand, all these have a stroker crank which gives a total of ~270 cu.in., yes, I AM a big fan of the turbo 4.1!