14th Sep 2014, 16:25
I own a 1985 Buick LeSabre with the updated, underpowered 307. And let me tell you it's hard to notice on paper, but compared to the older version, the 1985 and newer 307 is nothing short of a useless boat anchor. It is reliable and durable, but struggles nearly as hard as some of Buicks old carburated V6 engines to maintain a decent speed on the highway, or on hills in our modern world.
With as slow as my Buick is, I can't even fathom this motor in a car like the Brougham that weighs almost half a ton more. I bought my 1985 because it was a Collector's Edition, but unfortunately the engine is anything but collectible.
Regarding engine swaps, you would want to check if the bell housing from the 305 fits the transmission you are hooking it to. If it doesn't, usually you just need an adapter kit that matches the bolts up.
Also, if you are hooking anything bigger than a 305 to a transmission from the 1980s, you will want to have your transmission rebuilt. The 200-r4 transmission put in 1980s GM cars is not built to handle torque from any V8 larger than 5.0 liters (some did come hooked to the 350 diesel, but that was a boat anchor as well). Go to a performance shop that is familiar with Buick Grand National, Chevy Monte Carlo SS, Camaros, Firebirds, etc. While the 200-r4 is junk from the factory, you can install aftermarket shift kits and valve bodies for them to handle well over 500 pounds of torque; more than most stock V8s put out even today. They may be able to sell you a transmission cheaper than rebuilding your own. Just do some research. Do not go to your local transmission shop that is run by an old, dumb farmer. They know nothing about modifying transmissions; only changing fluids or doing complete replacements.
If it were me I would simply try to find a complete engine and transmission from a early 1990s Brougham or a 1992-1996 Buick Roadmaster. They are getting harder to find, but they are out there. You would need the computer from the newer engine to work in your older car.
That, or if you really like the Brougham, just try to find a good clean 1991-1992 with the Chevy 350. They are pretty spendy today though, and seem to be more prone to rust than a lot of GMs from that time period.
FYI almost all GM V6 and V8 small blocks and big blocks are interchangeable with the frames on all GM full and mid size RWD cars from the late 1960's onward. Sometimes the mounts and frames need to be slightly modified, but in the end they can all be easily made to fit. If you don't want to worry about matching all the electronic BS and pollution control stuff, find a Chevy 327 motor, or a good Oldsmobile 350 V8 or Chevy 350, and go from there.
14th Sep 2014, 15:18
Based on my experience with the 307, it has everything to do with the way it's been maintained. The 85 and later 307s used swirl port heads, and when they are running right, they are a pleasure to drive. Nice smooth throttle response, fairly decent pick up, and a nice hum sound - never a growl. The problem I've seen with them is carbon build up in the intake manifold, failed intake manifold gaskets, improper procedure when setting the ignition timing, and failed EGR valves that were misdiagnosed. Everyone will assume the carburetor is going bad, but it's usually those other things that throw the mixture off, causing sluggishness. It's usually never the carb itself.