When I purchased my 1971 Buick GS convertible almost 16 years ago, I knew I had found my dream car. Spending the $4,000 asking price was also a big step as that was pretty much all the money I had in the world, being a broke college student. Then just a month after buying the car, while cruising to Oklahoma City, on a date with my future wife no less, the stock Buick 350 lets loose at 70 MPH. The carnage was legendary- pieces of piston skirt came to rest at the bottom of the tranny inspection cover. There were three or four 6-inch long slices in the inspection cover. The only thing saving my right foot was a bellhousing bolt that didn’t shear off when the back of the cam hit the bellhousing, busting the entire ear, and bending the bolt. I never did find the last 3 lobes of the camshaft.
Needless to say, the block was history. I was seriously concerned about my situation as this was my only car, and I was broke. As luck would have it, a good friend just happened to have a 1971 Buick 350 4-barrel that he had pulled from his Chevy truck (that is another story all together) and offered it to me for free. We spent the next weekend dropping in the motor. I had no idea of the condition of the motor, but we fired it up and it ran, it was quite strong at that. 7 years later, the motor still ran nice, but the tell-tale blue smoke on start up and acceleration was increasing. The progress of the rebuild had reached a point where it would be sitting for a while anyway, so out it came, ready for a rebuild.
For muscle cars, the rebuild process offers 2 options, go stock and keep it all original or pump up the power and add some ponies to the mix. Since this motor was non-numbers matching, and a 350 to boot, we chose the latter. Most people out there are saying “What? A high-performance Buick 350? That’s crazy” Well, in reality, the only part that is crazy is how little aftermarket support there is for these small-block powerhouses. The original design of the Buick 350 differs so much from the traditional small-block Chevy that people are afraid of it. The long-lived rumors of bad oiling systems (unfortunately true, but easily rectified) and relative scarcity (built from 1968 to 1980) is harder to find than an SBC motor, don’t let that stop you, though, as these motors have quite a bit going for them.
Back in March of 2006, we ported the heads for this motor. The head design for the Buick 350 was ahead of its time, using tall, skinny ports to generate higher port velocities while keeping the air flow up as well. This helps the Buick create low-end torque as well as excellent mid and high-rpm horsepower. Adding to this is the under-square bore\stroke (3.80” bore, 3.85” stroke) which yields incredible torque. The Buick 350 has the longest stroke of all the GM 350 engines. The little Buick also features a deep-skirted block, higher nickel content, external oil pump and is 100 pounds lighter than the small-block Chevy. All of this adds up to an extremely durable motor, which with a little tweaking, is capable of supporting 1,000 horsepower.
Our goals are not that lofty, we are looking to hit 400 hp, retain a streetable demeanor, and longevity. Every part used in the build was an off-the-shelf part, no custom made unobtainium materials here. Some parts were tweaked to get the most performance and we used some unique tricks.
We sent the block to Jim Burek at Performance Automotive Engines in El Paso, TX. Jim has been building high-performance Buicks for over 20 years and is considered by many to be one of the best. Jim had the block machined at a local shop to his specs. The Buick 350 does not require a torque plate for boring as all of the head bolts are blind, meaning they do not hit the water jackets, so the cylinder does not tweak when the head is bolted down.
The block was bored .030”, crank and rods turned .010”, and the block was decked .030”. As it turns out, the 350 could have been rebuilt without boring or turning the block as it was in really good shape, but in order to get the tight clearances for high-performance use, the machine work was performed. Using Sealed Power Hypereutectic pistons, final compression for the motor came in at 10.1:1. The internal components for the engine were sourced from Poston Buick, a Buick-only specialty shop. The camshaft used in the motor is, well, big. Not for the faint of heart, we opted for the largest cam Poston Buick makes for the 350, with over .520” lift and 302 degrees of duration, you will hear the GS coming long before you see it. In order to tone down the low RPM effects of the cam, we used a set of Rhoades lifters which feature a high-bleed off rate under 2000 RPM. This essentially creates a dual-cam effect, where at low RPM, the cam is more subdued, but once the engine hits 2000 RPM, the lifters stay pumped up, allowing the cam to do what it does. They are a little noisy, but worth it in drivability.
Using Comp Cams’ Desktop Dyno software, we spec’d out the motor using the specs from the block and components used, which included the detailed airflow for the ported heads. The computer generated a power curve with an impressive peak 408 hp at 5500 RPMs; 430 ft. lbs. of torque at 4000 RPMs. Once assembled, the actual 350 was put through its paces on the Land and Sea engine dyno, and those results came in at 396 hp at 5300 RPMs; 414 ft. lbs at 4200 RPMs. That is just a few ticks from the computer-generated peaks. The motor makes peak horsepower under 6000 RPM, which is good since Buicks don’t like to spin past 6000. Not bad for an engine that has been all but forgotten.
1. The Buick 350 arrived on a pallet at PAE, sans heads, which had already been built. From here, the block was torn down and sent to the machine shop. The block was bored .030”, decked .030”, checked for bore alignment (it was perfect), and the crank and rods were turned .010”.
2. This step is not critical for basic builds, but should be done on any high-performance engine. The flashing around the lifter bores was removed. This will help hasten the oil’s return to the pan. When massaging cast iron, use a fine-tooth bit, coarse bits will jump around, causing more damage than good.
3. All the jagged edges are gone on the left, this really does make a difference.
4. Use ball end carbide to radius the oil gallery coming up from the oil pump into the passenger lifter gallery. Radius the back sharp turn, smooth and radius as much as you can. This will significantly improve oil flow.
5. Using a 12-inch long, ½ inch drill bit, the suction side oil galley from the front of the block to the oil pick-up tube was opened up. This passage is 10.5 inches deep.
6. The same procedure was performed on the oil pick-up tube passage. This will intersect with the previous passage from the front of the block. The depth on this one is 3 inches.
7. Using a 7/16”, 12-inch bit, open the oil feed from the oil pressure sending unit to just shy of front cam bearing. The hole depth is 4 inches. You can open this to ½ inch, but that will require re-tapping the oil pressure sending unit hole, to 3/8” pipe, from factory 1/4” pipe thread.
8. The main oil feed holes on #2, #3, and #4 mains were opened up from the stock ¼” to 5/16”. Be careful; make sure you go in straight so you don’t go off the edge of the cam bearing. You must go all the way past the cam bearing to a depth of 3 ¾” inches. This can be done with a standard drill bit.
9. Stock main bearings have 3/16” oil holes. Jim drills these to 5/16” to match the drilled block passage.
10. Measuring main bearing bores with the caps torqued and bearing installed.
11. The crank was measured with a micrometer. The difference between this measurement and the previous measurement is the bearing clearance, in this case .002.
12. The bearings were fit to the main bearing saddles. Notice the mis-aligned main bearing feedholes, this is even after the passages were drilled.
13. Using a pointed carbide burr, the hole was chamfered.
14. Oil passage now lines up with the bearing hole. Always check this, journals 2, 3, 4, and 5 had to be done.
15. Buicks used rope seals front and rear. Jim replaced the rope with neoprene. He added some small divots with an awl, where the seal goes, to give it some teeth to help hold the seal from turning. Then added a thin film of RTV so oil won’t leak around it.
16. The neoprene seal was installed offset about a ¼”, so the seal wouldn’t leak in the middle.
17. This is a grooved cam bearing with relocated oil holes, from the stock 8 o’clock location, to a more desired 4 o’clock position.
18. The front cam bearing was installed with the oiling hole at 3 o’clock. The 2, 3, 4, 5, and 7 cam bearings should be positioned at 4 o’clock.
19. The cam was installed along with the timing chain. It is a good idea to install the timing chain at this point as there is very little room between the rods and the cam. The rods can hit the cam if the crank is rotated and the cam is not. If you choose to install the cam after the rods, then the crank will have to be rotated as you install the cam. This is easier.
20. We used ARP main studs to secure the crank in the block.
21. Jim opened up the oil feed passage, in the timing cover to the block, to 1\2”.
22. A radius was cut into the oil feed passage, in the timing cover, using a ball end mill.
23. Jim checked the gear clearance in the oil pump housing. A clearance of .004 to .005 is good. If the clearance is .007 or bigger, the cover is junk.
24. The high-volume pump gears were installed in the timing cover. The gears must be packed in assembly lube or the pump will never prime. Buick 455 builders might stay away from high volume oil pumps, but there is no problem using one on a 350.
25. Using an oil pump thrust plate helps increase oil pressure, by eliminating cavities in the oil filter housing, as well as giving a new surface for the gears to run on, in the event the oil filter housing is worn from them riding against it, which is a very common problem.
26. The front seal was also replaced with a neoprene seal. No more rope.
27. A very thin layer of silicone sealant was used on the timing cover gasket. Use too much and the excess could fill an oil passage, and that would be bad.
28. The timing cover bolts were coated with anti-sieze as these bolts go through water.
29. The balancer was marked with a 30 degree location. This makes setting the ignition timing easier. Jim normally gets this 30 mark to 4 or 6 to give a total of 34 to 36 all in by 2200 rpm.
30. Make sure to resuse the factory windage tray. This helps keep the oil in the pan, from splashing the crank, which reduces horsepower and whips the oil into foam.
31. All done, the short block is complete. The Sealed Power Hypereutectic pistons from Poston Buick are a welcomed addition in place of the stock dished-out 8.5:1 slugs.
32. The heads were bolted on using ARP head studs. While studs may not make it easier to pull the heads with the engine in the car, they certainly add more durability in the head sealing department. The Rhoads lifters were installed and the engine was buttoned up. Now it is ready for the dyno.
Here are the readings from the computer and the dyno.
Here is the pricing list for this Buick 350 build.
Performance Automotive Engines