Re: V4/V6 family opinions & questions

[Don]

OK, I will try to separate the engine families to two basic groups:
V4-V6 cross scavenged engines
V4-V6 loop scavenged engines
The V4-V6 cross scavenged engines have been around since 1958. They are fairly rugged, and forgiving when it comes to cylinder wear/scuffs/scores. Generally speaking, their systems are simpler, they idle well, and most troubles are easy to diagnose. Today’s fuels have caused some problems with piston coking/ring sticking though.
The V4-V6 loop scavenged engines were introduced in 1985, alongside the cross scavenged models. I was excited about these engines when they were introduced, but lost enthusiasm for them within a few years. These engines are definitely better on fuel than the cross scavenged models, but tend to lack mid range pulling power. Because they are loop scavenged, they are relatively intolerant to poor piston fit/scuffs/scores. The fuel systems on these engines are very complicated, over engineered, and tough to diagnose. Some of my complaints were improved over time, 1993 brought significant improvements for the V6 loop powerheads. Later fuel systems were improved making adjustments and servicing easier as well. These engines do have a relatively complex fuel recirculation system that must work correctly to maintain decent idle quality.
There were so many minute changes to the gearcases, it is tough to say whether gearcases will swap between the two engine families….
The power trim units were a bit more interchangeable though, but the V6 loop trim unit is unique to that engine. The later model "fastrak" trim units were somewhat more interchangeable.
A good way to introduce yourself to these engines is to start with the cross scavenged V4 engines from the mid 70s thru mid 80s…