Pistons, Rods, & Cranks, Oh My! How to Build Horsepower With a Buick Engine

A strong engine starts with a strong crankshaft, and all Buick engines use quality cranks. This is good because there are not many aftermarket cranks for Buicks. The small- and big-block engines, as well as the 3.8-liter V-6 turbo, use nodular-iron cranks, while the Nailheads run forged-steel cranks. Some people will tell you that the only way to tell if a Buick crank is made of nodular iron is if it has an “N” cast into it. While this is true for some Buick cranks, it is not a steadfast rule. In 1970 and earlier Buick engines, many of the cranks were marked with the telltale N and manufactured in the Flint, Michigan, plant that produced nodular cranks as well as plain steel units. In 1971 and later, Buick used a foundry that only manufactured nodular cranks, which eliminated the need for the N.

Crankshafts

Nailheads

The Nailhead uses four different forged-steel cranks. These forged-steel cranks are used in the 1953–1956 264/322 and 364, 1959–1963 401 and 425, and 1964–1966 401 and 425. The two different 401- and 425-ci cranks were a result of the transmission converter hole on the back. The Dynaflow transmission, used until 1963, had a larger pilot hole in the end of the crank than the 1964–1966 crankshaft that used the ST300 and ST400 transmission. Nailhead specialist Russell Martin, sells an adapter bushing that fits in the rear of a 1957–1963 crank. He also offers a dual-pattern Nailhead starter. With this adapter and a 1964–1966 flexplate, the ST300 and ST400 transmissions can be installed on all 1957–1963 engines. However, the 1953–1956 engines use the same crankshafts except the factory stick shift, which had a smaller hole for a pilot bushing. Small, lightweight mini gear reduction starters are available from nailheadbuick.com and Tom Telesco. The Dynaflow starter has about a 1/2-inch longer snout so the shorter 1964–1966 starter or special mini starter must be used. The 1961–1966 block accepts the 1964–1966 starter as is, but the 1957–1960 block has a different starter bolt pattern.

 

 

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Small-Block 350
The smaller of the Buick powerhouses, the 350, does benefit from the same aftermarket support as its big brothers. The 350 had but one crankshaft, a cast nodular-iron unit. Fortunately, the stock crank is strong enough to support well over 500 hp. The 3.85-inch stroke crank will handle this magnitude of power, but the oiling system must be modified and the bearings need to be nice and tight. For power-added motors, such as turbos and superchargers, the stock crank is fine for engines up to 600 hp. If you plan on developing more than 500 hp, a custom crankshaft is required. Although expensive, the typical $2,000 price is cheap when you look at the overall price of building an extreme performance engine. Supercharged Buick 350 engines with stock blocks have been dyno’d at over 1,000 hp, so it certainly is capable of producing megapower as long as the right components are used.

 

One drawback of the 350 is that the engine is built so tight, and there is literally no extra space between the rods and camshaft for any additional stroke. As a result, the cam must be installed before the crank; otherwise the crank and rods have to be rotated during the cam installation. By installing a custom-ground crank and custom pistons, you can increase displacement by a few ci, but the expense does not justify the performance benefits.

Big Blocks

The 400/430/455 crankshaft is also made from cast nodular iron, but these cranks easily support up to about 800 hp. For engines spooling more than 800 hp, there are aftermarket alternatives. All of the big blocks use the same 3.9-inch-stroke crank. The late-1970 and later cranks were cast without the telltale N, so don’t let this confuse you; it is assuredly a nodular-iron unit.

The stock crankshaft has very large 3.25-inch main journals because these large main journals added critical strength to the thin block. In most applications, the stock crank is more than enough to provide a solid, dependable base for the rotating assembly, as long as it is properly prepped and oiled. When using large amounts of nitrous (200-hp shot or more) or building extreme-output race engines, a custom forged-steel or steel-billet crankshaft is necessary. The stock crank cannot handle the hit of a 200-hp nitrous shot for long. It might work a few times, but it will eventually break, and then every single part on that engine will be unusable. You can build a custom billet crank for about $2,500, but this process often takes 6 to 10 months.

 

 

 

 

For those who subscribe to the gearhead adage, “there’s no replacement for displacement,” TA Performance’s 455 stroker kits are a good option. The 494-ci and 523-ci stroker kits offer more displacement for extreme performance. The TA cranks feature 4.150-inch stroke and a 2.0-inch crank-pin diameter. Each stroker crank is custom ground, precision indexed, and magnafluxed. In addition, each crank has chamfered oil holes and is micropolished for superior oiling.

V-6 Turbo
There are two types of 3.8-liter V-6 turbo crankshafts: the nodular iron crankshaft used in the turbo engines, and the standard 3.8-liter crankshaft. The nodular turbo crankshaft features a rolled radius on the main and rod bearings that adds concentricity and uniformity, which increases load distribution through the journals. This also adds a good deal of strength to the crankshaft and reduces stress risers, which can cause catastrophic failure. All 1978–1987 turbo 3.8-liter crankshafts are nodular iron with rolled radii. The standard 3.8-liter cranks have rolled fillets on the main bearings only, and this crank will not survive in a turbo engine.

 

 

 

Main Seals

The Nailheads, the 350, and the big blocks used a factory rope seal, which originally sealed the crankshafts. But these seals were difficult to install and should be replaced with neoprene seals. There are, of course, a couple of techniques to make it easier.

 

The groove for the seal should be modified with three divots in the block and in the main cap. This keeps the seal from rotating in place. The grooves should also get a little squirt of silicone. The silicone seals the perimeter of the seal and keeps oil in the crankcase where it belongs. The neoprene seal comes in two halves. Each half should be installed with about 1/8 inch rotated out of one side of the groove (make sure they are opposite each other, top and bottom). This ensures there will be no leaking at the joint.

 

 

Connecting Rods

Nailheads
All of the Nailhead engines had forged rods. The 1953–1956 rods were 6 inches long and featured a wider bearing than the 1957–1966. There are two different rods: 1953 to mid-1955 264 ci and 322 ci; a pinch bolt held the wrist pin. On the mid-1955 to 1956 models, a more contemporary press-fit unit held the wrist pin, which was suitable for performance rebuilds. The 364 rods are 6-1/8 inches, and the 401 and 425 rods are 6-1/4 inches. The Buick rods are long for the stroke, so they have excellent rod/stroke ratios. This is even more evident with the 264, 322, and 364 engines. There are two different 364 rods, one used in 1957–1958 and one for the 1959–1961. The latter rod uses the 1959–1966 401 rod bolts and ARP bolts are available for these rods, but not the rods prior to 1959.

Forged Pontiac rods can be used in the 401 and 425 engines. These rods are longer and increase the rod/stroke ratio for better breathing. However, it takes a lot of work to make the 389 poncho rods for the Nailhead. These rods need to be lightened up and narrowed at the big end so the stock 401 bearing can be installed. The rod bolts hit the bottoms of the cylinders, so these must be clearanced on the block. The rod nuts contact the oil pan so a 1/4-inch spacer must be installed to drop the pan slightly. The Pontiac rod is 6-5/8-inch, and the 401-425 rod is 6-1/4-inch; therefore custom pistons with the wrist pin moved up are required.

Stock rods require very little work because they are forged and very strong. When rebuilding a Nailhead, a machine shop needs to magnaflux, shot-peen, and resize the rods and install ARP bolts. Always check the small ends of your rods, too. Buick had problems with wristpin knocking, and dealers installed oversize pins to fix it. If a standard pin is installed in these rods, it will slide out and ruin your cylinder wall.

Small-Block 350
The connecting rods for the 350 are quite durable and handle 500–550 hp, even though they are cast iron. When properly prepped, the stock rods are even suitable for all but the most extreme 350 builds. For prep guidelines, follow the steps in the next section for the big-block rods. While there are not many aftermarket Buick options, there are some. TA Performance offers reconditioned 350 rods that have been magnafluxed and shot-peened. In addition, the wrist pin end is checked for size, the crank end is resized, and ARP rod bolts are installed. TA Performance’s high-performance forged-aluminum connecting rod is an extreme-performance alternative. This rod is the strongest aftermarket Buick 350 rod available. Of course, it is the only aftermarket Buick 350 rod produced. This rod is ideal for racing or adding nitrous to your small-block Buick.

 

Machining other makes’ rods, such as Chrysler or Chevy, for the Buick 350 is another option. However, this is a very costly option and it yields a miniscule benefit. With the availability of the TA forged rod, the custom option just isn’t worth it.

Big Blocks
Buick installed forged-steel rods on the big blocks, which provides adequate strength for many highperformance applications. If the stock rods are properly prepared, they are even strong enough for racing, a nitrous oxide system, or revving up to 6,500 rpm. If you are going to spin the engine more than 6,500 rpm, the stock rods will not be strong enough. In addition, a set of aftermarket rods is required for a 125-hp, or more, shot of nitrous.

 

 

Numerous aftermarket connecting rod offerings provide a significant increase in strength over the stock rods. Some even provide a better rod/stroke ratio, but these rods require custom pistons. Chevrolet big block, Chrysler, and Pontiac rods require modification but can be adapted for use in a Buick, which opens up an entire selection of aftermarket options. Use of any non-Buick rod will require a custom piston. A big-block Chevy rod requires rod journal machining to accommodate the smaller Chevy bearing. Anytime you choose to run a non-Buick rod, the corresponding bearings and pins reference the rod type, not the Buick engine.

While there are lots of non-Buick rod options, there are quite a few aftermarket offerings, as well. TA Performance offers both forged-steel and billet-steel connecting rods. The 4340 billet-steel rods offer the most strength and lightest weight comparable to billet rods.
The length of the connecting rod is good for a little cheap HP. Some builders, such as Jack Merkel of Merkel Performance Engines, suggest that a 6.800-inch rod in the 455 engine will deliver a little extra power, but there is no more power to be found by using a longer rod. TA Performance, however, sells 455 rods up to 7.350 inches.

Properly prepping rods takes a little patience and time. When it’s done correctly, it yields a quality piece that will serve any vehicle well. When disassembling the motor, correctly label the rods for convenient assembly. The rods have matching caps that must be used with the same rod; otherwise, the bolts will not line up in the rods. Simply stamp each cap and rod on one side by using a mallet and set of number stamps. This ensures the rods are also installed in the right order and in the right direction. There is a small dimple on each rod, and each pair of rods must have the dimples facing each other for correct installation. Ask your machine shop to perform this process if it disassembles the engine. In addition, the shop should Magnaflux the rods and make sure they are not bent or cracked. Once the rods’ straightness and integrity have been verified, it’s time to get out the sander.

Use a belt sander with a small-diameter roller; or, a small-diameter sanding drum with medium-to-fine grit is ideal for removing the forging seam along the length of the rod. This reduces the stress risers, which accumulate heat and lead to cracking. Run the sander along the length of the rod, as you want the cuts to run the lengthwise instead of across the beam. An air-powered mini-belt sander works perfectly for this task. Once the rods are polished, a set of ARP rod bolts should be installed. At this stage, the rods are ready to be resized. A properly prepped set of rods should be good to 6,500 rpm without any issues.

V-6 Turbo
The 3.8-liter connecting rods used in all Buick V-6 turbo engines utilize a strong cap-screw design. This is the same design of connecting rod used in racing, including NASCAR. Introduced in 1975, this design proved to be twice as strong as the previous style. For most high-performance builds, the stock connecting rods provide more than enough strength for a turbo engine. In fact, rods are very seldom the cause of a turbo engine breakdown. The stock rods can take a tremendous amount of abuse.

 

There are several aftermarket rods available for those who are building extreme-performance and race-only turbo engines. K1 Technologies, a division of Carrillo, produces an H-beam 4340 forged-steel connecting rod fitted with ARP2000 rod bolts. These rods are suitable for just about any performance level turbo engine.
One note on the factory turbo rods: the bolt hole in the cap is not chamfered from the factory. This needs to be corrected when using aftermarket rod bolts, such as ARP. If not, the bolt head will not sit flush on the cap, and the bolt cannot be torqued correctly.

Rod Bolts

Always use ARP or similar high-performance rod bolts. They offer superior holding power and accurately measure bolt stretch. Reusing the stock bolts is never a good idea because these used stock bolts have been stretched, and they cannot be accurately measured and torqued. Save yourself a headache and pay the nominal amount for a set of good-quality rod bolts.

 

The rod bolts need to be torqued to the proper specs, or there will be problems with your engine. Too much torque can cause excessive friction in the engine, leading to bearing failure. Not enough torque and the oil pressure will lead to failure, as well. While the factory specs call for 35 to 45 ft-lbs for the connecting rods, most builders recommend 50 ft-lbs for high-performance applications. Once the rods are torqued down, the side clearance for the rods is an important clearance to be checked. There should be between 0.007- and 0.016-inch total clearance on the rod journals for performance rebuilds.

 

Pistons

Nailheads

The original Nailhead pistons on the 264 are 3-5/8-inch diameter and 4-5/16 inches on the 425. The 1953 has a very large dome — almost like a Hemi — while all others have the same basic dome shape. It is common for people to confuse a 10:1 Nailhead piston for a 12:1 piston because the dome profile makes it look like a higher compression unit. The large pent-roof chamber of the Nailhead cylinder head requires large piston domes, unlike the later Buick engines and most other makes. Buick used the size of the dome to change compression ratio of the piston. All factory pistons were cast, except a limited number of the 11:1 forged pistons for 401s offered in 1966. Cast pistons are perfectly acceptable for a Nailhead build. They are quiet when cold, and lighter than most forged pistons.

 

Some racers have claimed they lost horsepower by switching from cast to forged pistons. Max Balchowsky, who built the cars in the movie Bullitt and a Buick Nailhead authority, said he ran cast pistons in Nailhead engines up to 7,000 rpm. The 1954–1955 Buick 264 and 322 pistons did not provide sufficient durability. These pistons often cracked and should be replaced with aftermarket cast or forged. There are a couple of ways to finish off cast and forged pistons, including CNC machining and cam grinding. “I have had some problem with CNC’d pistons,” said Russell Martin, a Nail-head engine expert. “They don’t seem to have a nice wear pattern when I have inspected used ones, so I prefer old-school cam-ground pistons.” Computer numerical control (CNC) machining uses a computer aided design (CAD) program to operate the machine. Cam-ground pistons feature an elliptical-shaped cross-section. This elliptical shape allows the piston to fit in the cylinder regardless of being hot or cold and allows for more expansion.

 

Small-Block 350
The stock pistons, while decent, are not really suitable for high-performance use. The stock castings have a large, dished-out center with a little nipple sticking up. An easy way to identify the compression ratio of the piston is to look at the height of the nipple. A deep dish with a tall nipple is a low-compression engine. The stock compression ratios for the 1968–1980 350 are: 10.25:1 (1968–1969), 10.5:1 (1970), 8.5:1 (1971–1975), and 8.0:1 (1975–1980).

The 10.2:1 compression pistons are the only stock cast pistons currently available for the Buick 350. There are two types of aftermarket pistons: hypereutectic cast, and forged. To make an informed decision on piston selection, here is a brief description of each type.

The term “hypereutectic” means over eutectic, and eutectic is a metallurgical term that refers to the percentages of one element to another in a specific alloy for maintaining a common bond. Once the alloy reaches a certain percentage, any material that’s added remains a separate entity.

Typically, in aluminum alloys, the silicon content is eutectic at 12 percent. In the 1970s, it was discovered that adding more silicon to a cast piston produced less expansion when heated. This was very important for emissions, and it created a process of forcing additional silicon into the alloy, which remains in its granular form up to the 16 to 19-percent range. At 25 percent silicon, the pistons become hard and brittle and are subject to cracking.

Hypereutectic pistons can be machined for a tighter fit, and can run much closer tolerances in the cylinders because these pistons do not expand very much when heated. The rings form a tight seal on the cylinder wall, and this translates into less oil blow-by at start up. However, these pistons are not as strong as forged pistons and should not be used in any engine that uses more than a 125-hp shot of nitrous.

Forged pistons are formed from a heated slug of aluminum alloy. The alloy is forced into several increasingly detailed dies until it comes out as a very close representation of a finished piston. The forging is machined to precise specs and ready for installation. Forged pistons are very strong, and they can take a lot of abuse without breaking apart. Most importantly, these pistons are the only choice for any serious high-performance engine, but there are drawbacks.
Forged pistons are more expensive and fit more loosely in a cold cylinder than hypereutectic pistons because the forged pistons require loose tolerances to accommodate for a large expansion range. The expense of a forged piston depends on the engine. For a small-block Chevy, these pistons cost a little more than a cast piston. For a small-block Buick, however, they cost a bit more. As a matter of fact, TRW recently ceased production of the only production forged piston for the Buick 350. The other drawback is loose cylinder tolerances, which only affects the engines when they are cold. For basic mid-level daily driver engines, the strength of forged pistons would not justify the expense. For serious high-performance and race engines, forged pistons are a must.

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This Tech Tip is From the Full Book, HOW TO BUILD MAX-PERFORMANCE BUICK ENGINES. For a comprehensive guide on this entire subject you can visit this link:

LEARN MORE ABOUT THIS BOOK HERE

SHARE THIS ARTICLE: Please feel free to share this post on Facebook Groups or Forums/Blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https:// musclecardiy.com/pistons-rods-cranks-oh-my-how-to-build-horsepower-with-a-buick-engine/

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Currently, a forged piston is not available; custom pistons are the only option besides stock cast or hypereutectic. Several manufacturers produce on-demand, custom pistons for Buick 350 engines. Diamond Racing is one of those companies. TA Performance and Poston Enterprises also offer forged Buick 350 pistons in a variety of compression ratios. Hypereutectic pistons for the Buick 350 typically have a 10.5:1 compression ratio. The price difference in a custom forged Buick 350 piston and a hypereutectic piston is typically $300 – $400. The Sealed Power hyper-eutectic piston is probably the most commonly used Buick 350 piston, and we used this piston on our 400-hp 350 build-up.

Big Blocks
The big blocks, predominately the 455, have quite a few brands of pistons available. As stated earlier, stock cast replacement pistons are not suitable for any application other than stock rebuilds. For high-HP engines, forged pistons are the best choice. In fact, forged pistons are required for any big-block engine that will turn more than 5,500 rpm or use more than a 125-hp shot of nitrous. The premium material for forged pistons is 2618 aluminum alloy because it’s both strong and light. In most cases, a thinner 1/16-inch file fit ring is used. For most street or light stripduty engines, the TRW forged pistons fit the bill. Beyond running a custom piston, there are several specialized forged pistons available for the 455. TA Performance offers a 2618 alloy lightweight race piston in 12.0:1 and custom compression ratios. This is the piston of choice for building a stroker engine. These stroker pistons also have the top ring placed higher on the piston, reducing the compression distance. In addition, this accommodates a longer rod for better rod ratios. TA also carries forged stock replacement pistons available in 8.5 and 10.1:1 compressions.

 

The camshaft used in any particu larbuild may require notched pistons, so it is wise to speak with your cam supplier before ordering pistons. If your block has been decked or the heads have been milled, valve notches may be necessary. It is very important to dry-assemble your engine before final assembly to check valve clearance. A minimum piston-to-valve clearance of 0.100 inch should be maintained. A piston hitting a valve would not be a good way to break-in an engine.
Piston-to-wall clearance is also an important issue to consider. Inadequate piston-to-wall clearance can cause an engine to run hot. This is why most builders recommend honing every engine with torque plates. If you hone a block without a torque plate, you may have tight spots in your piston travel because the cylinders can potentially tweak when the head is torqued in place. Still, quite a few Buick builders dispute the value of torque plates for Buicks and will not use them. The choice is yours. For cast pistons (including hypereutectics), a clearance of 0.0015–0.002 inch is sufficient. The TRW forged pistons should run 0.003 to 0.004 inch of piston-to-wall clearance. Always follow the manufacturer’s instructions when using custom pistons. For most 2618 alloy pistons, at least 0.005- to 0.006-inch piston-to-wall clearance is required.

According to Mike Tomaszewski, owner and founder of TA Performance, “We do not sell, nor do we recommend, hypereutectic pistons. We have noticed an increase in failures due to the use of these types of pistons.” There are a few manufacturers that offer a hypereutectic piston for the 455, but these pistons are certainly stronger than the OEM cast piston and feature valve notches for use with larger camshafts. In addition, they are available in higher compression ratios than the stock cast pistons with their smaller dish and 0.010-inch less deck clearance. These hypereutectic pistons cost considerably less than forged pistons. TA Performance does not recommend these pistons because several customers have experienced piston breakage. In their opinion, hypereutectic pistons are too hard and brittle, allowing detonation to break a hypereutectic piston. This is an area of great debate. TA Performance is not alone in this argument, and they are certainly not opposed either. Many builders use hypereutectic pistons for high-performance street build-ups. It is this author’s opinion that there is a place for both.
The stock cast piston is not suitable for anything other than a stock rebuild. If you are building a mid-performance engine that’s below 600 hp for big blocks and less than 450 hp for the 350, the hypereutectic pistons will be more than adequate and should prove to be excellent in a properly built engine. With that said, do not use large amounts of nitrous on a hypereutectic piston. These pistons cannot take the shock and will break. A stock engine with stock cast pistons can typically take a 125-hp shot of nitrous. Use any more and you will start breaking pistons. If you plan on using nitrous, it would be a wise choice to use forged pistons. The same goes for any engine that is going to be revved over 6,000 rpm. If you are going to rev your engine this high, it is probably not a daily driver. If it will be raced, forged pistons are a must.

Turbo-V6
The pistons for the 3.8-liter V-6 turbo engines require special consideration. The forced-air induction engines place incredible demands on these pistons and make selection critical. The compression ratio for a turbo engine should not exceed 8:1 because a higher compression ratio can cause detonation, which can lead to engine failure. While high-octane or race fuels can remedy detonation, most owners don’t want to deal with hassle and/or expense of finding and running race-type fuel in a street car. Forged pistons are the best option for performance turbo engines because cast and hypereutectic piston are generally not strong enough to handle high-boost pressures. In fact, cast and hypereutectic pistons, if subjected to high enough intake pressures, can break apart in the cylinder and wreck the engine. Non-turbo pistons are not engineered or manufactured to withstand heat and stress of a turbo engine, so never use these pistons. The ring lands on a turbo piston are strengthened to support the boost pressure. Jack Merkel of Jack Merkel Performance engines recommends using TRW forged pistons with a piston to cylinder wall clearance of 0.0045-inch. Otherwise, you should follow the recommendations of the particular piston manufacturer. Piston weight is also a factor. Heavy pistons create more rotating mass and lose a fair amount of HP. Lightweight turbo pistons, made of 2618 aluminum, are recommended and provide superior performance.

 

Piston Pins

There are two types of wrist pins: press-fit and free-floating. Press-fit means the pins are pressed into the piston and rod. This wrist pin style has slightly more friction, so the pin remains stationary and the piston rotates on the pin. Controlled heating of the wrist pin side of the rod allows the pin to slide through the rod. As the rod cools, the pin is grabbed by the rod and held tight, leaving no possibility of the pin sliding out, ruining the cylinder walls. This is the most common method for Buick pistons. Jim Burek of Performance Automotive Enterprises recommends this style for all but race-only engines.

Free-floating wrist pins require honing the small end of the connecting rod so the pin can slide though easily. The wrist pin is held in place with two locking rings on both sides of the pistons. Some builders say these clips are prone to breakage. If one breaks, the pin can slide out and destroy the cylinder wall. Free-floating pins reduce friction and may free up a little HP on high-revving race engines, and they are certainly easier to assemble and disassemble. It’s a big plus for a race engine that gets torn down frequently. For street applications, they just are not necessary.

 

 

 

 

 

 

 

 

 

 

Rings

There are quite a few choices when it comes to piston rings. For stock and street-performance engines, a chrome-moly ring set provides good sealing and oil control. For high-horsepower and high-revving engines, the Federal Mogul or Speed-Pro plasma moly rings with a 1/16-inch-wide top ring is the best choice. These rings have superior resistance to moly flaking. The plasma coating increases lubrication, and the high melting point of the moly ensures a higher resistance to scuffing. When in doubt, use the plasma moly rings. If you are running nitrous, the plasma moly rings are the best choice because of the high resistance to heat and detonation. Most engine builders recommend a file-fit ring set. This allows the builder to set the gaps rather than use a by-the-chart gap in a standard set. Any high-performance application requires file-fit rings. Gapless rings, such as those from Total Seal, are not recommended for street engines. These rings feature a zero-gap second ring that interlocks, virtually eliminating combustion gas escaping through the rings. Removing the end gap can improve sealing, cooling, and HP. Some claim as much as a 5 percent hp increase by using a gapless top compression ring. Using a gapless top ring can eliminate the second compression ring on drag-race only engines. Deleting the second ring reduces friction and adds HP. But this is not something you would want to run on street engines. It’s for drag-race-only engines that get torn down after every race.

There is a lot of debate on this subject. In fact, many top builders recommend running a larger gap in the second ring because it reduces the pressure buildup between the rings. When the pressure drops, the top ring loses its seal at high rpm, resulting in better compression, better piston cooling, and reduced oil consumption. Pressure build-up between the rings will eventually force oil out of the rings, reduce lubrication, score the cylinders, and inevitably ruin the engine. By opening the gap on the second ring, the top ring is allowed to float, increasing sealing and allowing the gases to escape. This eliminates the possibility of the top ring lifting off the ring land.

After the type of rings has been selected, the file-fit process begins. Each ring is inserted into the cylinder bore, and a piston is used to push the ring inside, keeping the ring square. A set of feeler gauges is used to measure the gaps. Then each ring is filed using a ring grinder (available from Powerhouse tools, Snap-On, Matco, K-D, etc.) to keep the edges clean and burr-free. You could use a hand file, but why waste all that energy and time when a $40 tool does a better job? The ideal gap for the top ring is 0.016 to 0.018 inch, and the second ring is commonly set at 0.012 to 0.014 inch. The oil rings typically do not need sizing.
When the rings are sized, they need to be installed on the pistons. Opinions vary, but many contend that keeping the gaps apart is important for good sealing. Jim Burek, of Performance Automotive Enterprises, recommends setting the oil-ring spacer with the gap over one of the wrist pins. One oil ring is placed about in the middle of the piston between the wrist pins on one side. The other oil ring is placed 180 degrees opposed on the other side of the piston. The compression rings are typically installed with one gap over each wrist pin. It’s important to keep the gap opposed for the initial installation. The rings will move once the engine is running, so starting off with them opposed is the best bet.

Max-Performance 1970 Buick Gran Sport 455

Mike Garrison, owner of mrbuick.com, a Buick-specialty restoration shop, drag races this 1970 Buick GS as often as he can. TA Performance and Ruge Automotive built the bored and stroked 455 that runs as fast 10.18 seconds at 135.30 mph in the quarter mile. His business offers parts, such as core support rebuild kits, flywheel covers, and transmission brackets.

Engine Package:
• 535-ci V-8, 830 hp at 6,300 rpm; 802 ft-lb at 4,600 rpm
• 4.30-inch bore x 4.50-inch stroke
• 13.96:1 compression
• Steel billet 7-inch connecting rods
• TA 1610 inverted dome pistons with 1/16th rings, pin size: 0.927 inch x 2.950 inch, double spiral locks, piston weight: 546 grams
• Intake valve 2.19, 0.372 stem; Exhaust valve 1.75, 0.372 stem; Dual springs TA1190; seat pressure 230 lbs, open 540 lbs
• Comp Cams roller cam, 0.636 lift, 1.6 rockers 107-degree centerline
• 296-degree duration
• Cam degreed to 105 degrees
• Push rod size is 9.50 inch x 0.312 inch
• TA Street Eliminator heads: 58 cc Intake side flows: 334.9 cfm at 0.600 inch Exhaust side flows: 243.8 cfm at 0.600 inch
• Block supported with a block girdle
• Block is filled 50 percent with block hard
• Lifter gallery has been filled to the top of the bores with epoxy

 

 

Measuring Piston-to-Value Clearance by Len Emanuelson

Building a high-performance engine with various speed parts is complex business. To help avoid problems, you need to follow the basic engine-building rules, measuring every part to ensure they meet specs and trial-assembling the engine to check clearances. Valve-to-piston clearance is one of the most critical clearances and should be physically checked. Many first-time engine builders try to calculate the amount of valve clearance by the piston at top dead center (TDC) and the total lift at the valve. It just doesn’t work that way. You won’t know if the valve notches in the pistons are in the right place and exactly how everything meshes unless you go through the process. The most accurate test is to put clay on the top of the pistons, install the cylinder heads and valvetrain, and rotate the engine through a complete cycle — two complete revolutions.

Clay-Mation

Most professional engine builders recommend 0.100 inch for manual transmissions and as close as 0.070 inch for automatic transmission vehicles. Use 0.100 inch to be safe — and even more if you can get it — unless you’re building a world-championship race engine and need every bit of compression you can get. One missed shift at 7,000 rpm and valve float could instantly turn an expensive engine into a pile of junk. First, rinse the piston top with lacquer thinner for a clean, oil-free surface that clay can stick to. Then cut a couple of strips of clay about 3/16-inch thick and place them where you think the valves could hit the piston.

 

Engine Rotation

Spray the valves with a light coat of oil to prevent them from sticking to the clay and put the cylinder head back on the engine with a head gasket; torque to spec. Next, install the valvetrain and adjust the valve lash. Here’s the tricky part. Swap the hydraulic lifters for a mechanical lifter, a piece of wood dowel, or an aluminum slug that matches the pushrod seat height in the lifter. Why? A hydraulic lifter in a non-running engine will deflect the plunger and not give you true valve lift. In addition, you can take an old hydraulic lifter apart and fill it with something solid so the pushrod seat remains up against the retaining clip. Once you figure out this little issue, the rest is easy. Finally, rotate the crankshaft through two complete rotations. Slowly turn over the crank and feel for any resistance. If the engine doesn’t want to rotate completely, don’t force it. Remove the cylinder head and see what’s hitting.

 

Squish Check

Once you’ve successfully run the crankshaft through two complete revolutions, remove the cylinder head and inspect the clay. Hopefully, the clay was placed in the right location and stayed put for the valve opening and closings. (By cleaning the piston, the clay has plenty of stick, and by spraying the valves with light oil they won’t stick to the clay.) If you used thick-enough clay, the valves should leave fairly large impressions that are easy to identify.

 

Measurements

To determine valve-to-piston clearance, measure the deepest part of the groove made by the valve in the clay. Also, you must measure the deepest groove at the highest portion of the piston dome. Our Buick pistons had a big dish in the center, so the clearance was more than adequate. However, out on the raised edge of the piston, we measured the clay thickness with the wire-rod depth gauge of our dial caliper and measured only 0.075-inch clearance — just enough to squeak by. This big Buick red-lines at 6,000 rpm, and the automatic transmission should provide the safety factor.

Perform this valve-to-piston inspection when you trial-assemble your engine — you’ll be doing yourself a favor. Inadequate clearance means disassembling the engine, having the pistons notched at a machine shop, and starting the assembly process all over — a real pain!

 

 

Written by Jefferson Bryant and republished with permission of CarTech Inc

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