What was the last year for the slant?

mcnoople said

It is possible to make a 90 degree v6 that is smooth as silk and has a high redline. Gm just never has had the best powertrain engineers. The engine family in this link powered luxury cars and 8000+rpm supercars and all were 90 degree v6's. I have driven the 3.2 and 3.5 variants and they are smooooth. http://en.wikipedia.org/wiki/Honda_C_engine

Click to expand...

From the Wikipedia srticle:
"The engine utilized a 90 degree V-angle to the crankshaft in preference to the taller but more common 60 degree design, with a compression ratio of 9.0:1. The crankshaft had crankpins offset 30 degrees..."

That is really interesting. I never knew that.

The crankpin offset on some of the "almost even-fire" 90 degree V6's is 18-degrees, which was a compromise aimed at (probably) maximizing crankpin overlap in the interest of component strength at the expense of smoothness. I think (but don't know) that the 4.3-liter Chevy motor had this feature.

The bean counters often had their way (particularly, with lower-priced cars) when it came to balancing (no pun intended) cost vs. NVH issues, so we have a variety of designs out there.

I guess the inherent design features of inline sixes made balance shafts and any sort of compromise on crank design, unnecessary. I think some of the early Chevy sixes (215 or maybe 230) didn't even have counterweighted cranks... so good was the original balance...