When I was looking for a Willys pickup to buy, I planned to change the engine to one that was more modern and had more power than the original in-line 4 cylinder engine. A V8 really had too much power, and would cause cooling issues. There was not enough room for an in-line 6 cylinder engine in the Willys that I had (later years would allow this). So I started looking at V6 engines. I liked the Buick 231 (3.8L) V6. I didn't want a 225 Buick because the head doesn't flow nearly as well as the 231. I didn't want a Chevy 4.3 L V6 because of the firewall clearance issues with a rear mounted distributor and because I wanted to minimize engine electronics.
I planned to use a 4 barrel carburetor, a performance torque/economy intake and a mild "RV" camshaft. I decided on an Edelbrock Performer-Plus camshaft and Performer intake manifold. I used Desktop Dyno and the Edelbrock website to estimate the power and torque. Shown below are the 2 estimated engine outputs:
Desktop Dyno does not estimate output below 2000 RPM, but the torque is already coming down from 280 ft-lbs at that point. The power estimate peaks at about 180 hp at 4000 RPM. The Edelbrock website has a torque peak estimated at 3000 RPM of 220 ft-lbs. This tells me that 5000 RPM is a useful upper RPM point. The different estimates on the RPM of the torque peak causes a problem, since a torque converter is supposed to have a stall speed just above the torque peak. But at this point, I will use a torque converter with a stall speed of 1800 to 2000 RPM.
The Engine Purchase
Internet research showed that I needed a block from between 1977 1/2 (the change over from odd-fire to even-fire) and 1985 for a rear wheel drive application, and heads from 1979 to 1985 because the ports flowed better. After 1985, the engines became harder to use with a carburetor.
I bought a used Buick 231 V6 on Craigslist. It had a 1979 block, 1984 heads and had been built by an off road enthusiast with an Edelbrock Performer-Plus camshaft and some mild porting work.
Buick 231 Oiling Modifications
Other Internet research pointed out that the oiling system of Buick engines from those years is relatively weak. The oil pump needs a booster plate to tighten tolerances and control wear, and an adjustable pressure relief valve to make adjustments easier. The main bearing clearances need to be tighter than a typical Chevy - Buick engines rev lower and need tighter bearings to keep from losing oil pressure going to the rod bearings. And all the oil to the passenger-side valve train goes through the front cam bearing, so this bearing needs to have grooves on the back to allow oil to flow across it. The timing cover benefits from having the oil passages smoothed out, and the oil gallery passages on the block may need to be drilled out to allow more oil flow.
Blueprinted oil pump gears
Front cover modifications
Buick oiling improvements
Other Engine Parts
The engine is finished using mostly stock parts, except for the items below.
Power Steering Pump & Bracket
The power steering pump I'm using is a Saginaw P-Series pump. I picked a Jeep CJ7 model from 1980 or later because it has an o-ring seal. The Buick 225 or 231 engine did not always come with power steering, so I bought a set of 3 brackets on eBay. These were advertised for a 1970 Buick 350 (V8) engine. It is important to get all 3 bracket parts.
The 2 stamped steel brackets mount to the power steering pump with two 3/8"-16 nuts and two 3/8"-16 screws that are 3/4" long at maximum (they have to fit under the pulley). The triangular bracket fits to the block on the driver's side with two 3/8"-16 x 1" screws and a 3/8"-16 x 4.5" screw for the bolt that adjusts the tension on the drive belt. The pump pivot point is secured with a 3/8"-16 x 3.5" screw and nut. The final pump angle is tilted a little toward the driver's side - just FYI.
Alternator and Air Conditioning Compressor & Brackets
The used Buick 231 V6 engine came with an alternator bracket that mounts to the passenger's side of the engine. There was no mount for an AC compressor.
I want to mount a Sanden 508 compressor, since these are considered highly efficient and compact. Mounting an AC compressor is a challenge:
So I'm now thinking of making a custom mounting plate/bracket for the passenger's side of the engine that mounts the Sanden 508 AC compressor and the alternator.
The pulley system is redone with March Performance pulleys - a triple belt pulley on the crankshaft (March P/N 4221) and a triple pulley on the water pump (March P/N 4222). The power steering pump is driven with the stock single pulley on the power steering pump, and drives off the inner (rear) pulley groove on the crankshaft. The alternator currently is driven with the stock single pulley on the alternator, and the drive belt goes around the middle groove of the crankshaft pulley and the inside (rear) groove of the water pump pulley.
The final installation may require a double pulley on the alternator so that I can move the alternator drive belt forward 1 pulley groove to make room for the AC compressor drive belt. I have not yet mounted the AC compressor, so I don't know if a single groove or double groove pulley is needed on the compressor. The AC compressor will likely be driven with a single belt, but the double groove pulley might be needed to space the pulley to the correct position. The AC drive belt will likely go around the middle or outer (forward) groove of the crankshaft pulley and the inner (rear) or middle groove of the water pump pulley, and will be tensioned with the AC compressor.
There is an outer (forward) groove on the water pump pulley that is not used.
All the belts are single V belts that are 1/2" or 9/16" wide at the top (widest) part. The power steering pump works with a 49" long belt. It looks like I will be using a 41" long belt on the alternator. I haven't mounted the AC compressor, so the length is not determined yet. But it will be longer than the alternator belt.
Buick 231 Engine Resources: