A complete Pontiac engine can make an excellent usable core, but many of those now available may not be large enough or contain the best components to produce the desired amount of horsepower. While the aftermarket has heavily supported many other makes for several years, the number of choices for Pontiac hobbyists has been quite limited. But that isn’t the case any longer. Virtually any component possibly required when rebuilding a Pontiac V-8 is being produced in some form, and often the choices are an easy way to increase output.
This Tech Tip is From the Full Book, HOW TO REBUILD PONTIAC V-8S. 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 article on Facebook, in Forums, or with any Clubs you participate in. You can copy and paste this link to share: https://www.pontiacdiy.com/rebuild-pontiac-v-8-aftermarket-parts/
The stock Pontiac block is quite adequate for most high-performance rebuilds. It accepts an overbore of up to .060 inch in most instances, and possibly more after sonic testing to measure thickness. Boring routinely adds 5 to 12 ci depending upon the engine, and that can allow it to produce slightly more power while still operating reliably. Though complete block failure is rare, the stock block does not tolerate certain instances of grossly increasing displacement or greatly increasing performance level beyond its design capability. New blocks that contain additional material in critical areas, such as the deck surface, cylinder walls, lifter galley, main saddles, and oil pan rail, are available for hobbyists looking to go to the next performance level.
Two separate companies currently produce unique aftermarket Pontiac blocks that are commonly used when building engines that displace 505 to 535 ci or more. K&M Performance produces the MR-1, which is available in cast iron or cast aluminum. The IA-II block is produced by AllPontiac.com and is also available in iron or aluminum. Either is sold by a number of Pontiac vendors. The blocks contain external dimensions similar to an original Pontiac unit, but are generally thicker throughout and feature standard splayed 4-bolt main caps. The blocks are delivered fully machined, and accept most original Pontiac hardware. The basic iron offerings start at several thousand dollars and a number of options are available.
Pontiac’s cast-iron crankshaft is a durable unit. Rarely does failure occur from fatigue during common operation. Secondary factors like vibration, detonation, or lubrication issues are more likely the root cause of a failure. The journal surfaces can generally be renewed with proper machining, but there are certain instances in which an original Pontiac crankshaft simply isn’t reusable. While locating and using a suitable core is certainly possible, a few companies produce new Pontiac V-8 crankshafts, which are readily available from most Pontiac vendors.
There are two types of new Pontiac crankshafts presently available. Using world-market material and overseas labor, several companies source a common cast crankshaft, which is finished to proprietary specifications. The overall quality and finish of the cast units was once questionable, but has improved in recent years. Modern cast units are suitable for stock-type rebuilds and possibly even some high-performance rebuilds producing 500 hp or slightly more. With a relatively low cost of about $300 (or less), and a wide array of journal and stroke dimensions available, aftermarket cast-iron crankshafts are an acceptable solution to salvaging an original.
The second type of aftermarket Pontiac crankshaft is constructed of forged steel. These units generally cost a few hundred dollars more than their cast counterparts, but are considerably stronger and a better choice for high-performance rebuilds producing more than about 550 hp and up to about 1,400 hp. A steel forging is mandatory in any maximum-performance effort, however. Though the number of journal and stroke configuration choices has been limited in the past, there seems to be a wider array available today, and the cost has become much more reasonable. Those who have direct experience the aftermarket forgings report excellent results.
Pistons and Rings
Cast-aluminum pistons were used in nearly all production Pontiac engines from the start of production until the end. High-quality stockreplacement cast pistons are produced by a few different manufacturers such as Sealed Power and Keith Black SilvO-Lite, and are readily available from a number of mail-order vendors at a very reasonable cost. As of 2010, a cast piston set costs around $300. Keith Black also offers a cast-hypereutectic piston, which is a modern siliconaluminum alloy used to cast certain pistons. It is considered a step better than conventional aluminum, and adds about $100 to the set cost. While either type of cast piston can provide an owner with a long service life, it seems as if premature failure can occur if the pistons are not installed exactly as the manufacturer suggests and the engine operating conditions are anything but ideal.
Forged-aluminum pistons are far more forgiving. Most Pontiac vendors can supply you with a highquality forging at a reasonable price. While manufacturers such as Ross or Diamond produce custom pistons that fit a specific application, Sealed Power, Keith Black, Probe, and JR Pistons are just a few of the companies that produce off-the-shelf forgings that are a direct fit for the Pontiac V-8, which start out around $400 per set. If your rebuild uses a stock-stroke crankshaft and stock-length connecting rods, then stock-replacement forgings are an excellent choice. Custom pistons are required when using a long-stroke crankshaft or aftermarket connecting rods.
Working in conjunction with the pistons, piston rings are designed to keep compression and combustion pressures from passing around the piston and into the crankcase while lubricating the cylinder walls. Piston rings are commonly constructed of many different materials such as iron and stainless steel, and are usually moly coated. Depending upon the application, ring sets can come pregapped for a certain size of bore, with overlapping ends for custom gapping, and those designed to be completely file fit. Piston rings come in various thicknesses. Thicker ring packs tend to seal better while thinner ring packs tend produce less drag at high RPM, which can translate into more performance. There are distinct advantages to the various types of piston rings available and your machinist or Pontiac vendor can suggest the set and type that works best with your application, whether it’s for high-performance street, street/strip, or race.
A connecting rod is among an engine’s most stressed component. In constant motion, it is designed to endure compressive loads while changing direction several times each second without fatiguing. The severe operating conditions make reusing high-mileage cast-iron units a questionable endeavor, especially if engine output or maximum engine speed is significantly increased. Original cast rods can be reused in stocktype rebuilds if your machinist finds them to be crack free and in good reusable condition. While some hobbyists have taken extra steps to increase strength such as beam polishing and shot peening, I think the cost of modern forged replacements is a much better investment.
Though Pontiac used cast rods in most of its passenger car engines and failure during normal operating was quite rare, its specialized highperformance engines received heattreated steel forgings. The originals were expensive and difficult to find and remain so today. For years only a small number of Pontiac-spec forged rods were available on the aftermarket, and they too were once very costly. Modern forgings, however, make upgrading to a forged-steel connecting rod a much more sensible option during any rebuild.
RPM International has developed an entry-level connecting rod for Pontiac V-8 engines constructed of forged 5140-steel. The stock-style RPM rod, an I-beam design with dimensions identical to a standard Pontiac unit, is an affordable choice for any application where a cast-iron original is being considered. The unit is marketed under various names, available from most major Pontiac vendors for under $300, features 7/16-inch American Racing Products (ARP) bolts, and is suitable up to roughly 500 hp. I selected these rods for the 400 rebuild featured in this book.
Upgrading to 4340-steel forging is a worthwhile investment for any engine, especially if you’re planning an engine rebuild that generates more than 500 hp and up to about 800. A 4340-alloy steel rod is chosen for its desirable endurance qualities, and a number of companies offer such connecting rods specifically for Pontiac V-8s. Along with RPM International, Scat Enterprises and Eagle Specialty Products are other companies that produce 4340-steel rods for Pontiac applications.
It’s likely that the raw forgings may come from the same overseas supplier, but the cost of similar rods can vary between $300 and $500 per set. The price difference generally reflects of the number or types of finishing steps performed. So it may be worthwhile to purchase a more expensive set of connecting rod if your budget allows, especially when considering that there are no negatives associated with a connecting rod that’s too strong for a particular application. Other connecting rods constructed of billet-steel or aluminum are required for specialized applications where the specific strength and/or lightweight characteristics are required to withstand output or RPM. These units are available from manufacturers such as Carrillo Industries, Crower Cams and Equipment Company, and Oliver Racing Parts, and can be quite costly.
Adding engine displacement is an easy way to increase output, and the most common method when rebuilding a Pontiac V-8 has simply been enlarging bore diameter. Lengthening crankshaft stroke is another popular method, but the process is quite involved if you’re using an original Pontiac crankshaft. It requires resizing the crankshaft’s rod journals from the stock Pontiac diameter of 2.249 to 2.1 inches, ameasurement more closely associated with big-block Chevy engines. The rod journal is then offsetmachined in the process, which relocates the axis and allows stroke to be lengthened by .040 inch or slightly more, adding another 6 to 8 ci of total displacement.
With the somewhat recent availability of aftermarket Pontiac crankshafts with a wide array of journal and stroke dimensions, many vendors brought to market complete rotating assembly kits that include a new crankshaft, forged-steel connecting rods, forged-aluminum pistons, and the required rings and bearings. The crankshaft usually features a stroke length of 4.21 to 4.25 inches and 2.1-inch rod journals. It is combined with 6.8-inch connecting rods, which are also normally associated with big-block Chevy engines. Complete stroker kits make it much more practical and affordable to build a stroker engine, and increase the displacement and power output of most Pontiac V-8s.
The valvetrain is comprised of many components and the camshaft is at the heart of it all. There are four major types used in modern highperformance engine rebuilds and general terms are used to describe them. Hydraulic flat-tappet and roller camshafts use tappets, or “lifters” as they’re more commonly known, that rely on pressurized engine oil to continually adjust an internal plunger, which ensures that the valvetrain components remain in constant contact for quiet operation. Manual-lash flat-tappet and roller camshafts, which are often referred to as “mechanical-” or “solid-” units, require that valve lash be set manually.
A hydraulic flat-tappet camshaft operates quietly and consistently, and requires very little maintenance. The sheer number of available grinds from most camshaft manufacturers makes them a popular choice. They remain an excellent choice for any Pontiac engine regardless of intended application. However, at high engine speed, certain lifters don’t have sufficient time to bleed down (causing the valves to float), and that is the only real negative associated with them. Engine speed in excess of 6,000 rpm is quite possible if high-quality lifters are used. I prefer those from Comp Cams, Crane Cams, or Crower.
A solid flat-tappet camshaft uses a lifter with a fixed pushrod cup. Beyond the suggested amount of valve lash, the lifter transfers the entire lobe profile to the rocker arm, which can add several horsepower at high RPM. The valve lash can make a solid cam noisier than a similar hydraulic unit, however. Vintage lock nuts were good for one or two adjustments and could back off during normal operation, and that meant that valve lash had to be checked periodically and adjusted as needed.
Modern rocker arm studs with flat tops and positive locking nuts have essentially eliminated the need for continual valve lash adjustments, but many believe that regular valve lash maintenance is still required. That reputation tends to limit the popularity of solid flat-tappet cams for street applications today. When combined with ARP rocker studs and lock nuts, solid flat-tappet cams are quite reliable and can be checked annually, but should require no adjustment. In fact, if any lash adjustment is required, it may actually indicate abnormal valvetrain wear that should immediately be inspected for.
Hydraulic roller camshafts have become quite popular in recent years. Instead of a flat-tappet lifter that rides on the lobe, a specific lifter fitted with a roller wheel is used to reduce friction, and that allows for a camshaft with a more aggressive lobe profile. Both factors can equate to a slight performance increase when compared to a similar flat-tappet.
At one time, the relatively heavy roller lifters and the valvesprings required to control them at high engine speed caused the lifters to bleed down uncontrollably. That led to a poor performance, which gave hydraulic roller cams a negative reputation early on. The quality of modern lifters has improved significantly in the recent years, and the lifters from companies such as Comp Cams, Crane, and Crower can operate reliably up to 6,000 rpm and possibly more.
The most popular type of camshaft for serious performance applications is a solid roller. Like a solid flat-tappet, the roller wheel on the lifter follows the lobe and there’s no hydraulic pressure to compromise valve action. The friction reduction allows for a much more aggressive lobe profile, which opens and closes the valves at a much quicker rate and can increase performance. But the valvesprings and components required to control that action make a solid roller cam unpractical for street-driven applications.
An engine sees camshaft duration and lift at the valve. The lifter transfers camshaft lobe lift to the rocker arm, where it is converted into valve lift. Gross valve lift is easily calculated by simply multiplying lobe lift by the rocker arm ratio. Pontiac’s stock ball-stud rocker arm features a 1.5:1 ratio, and when used together with a typical Pontiac cam with .271 inch of lobe lift, gross lift at the valve calculates to approximately .407 inch.
While stock-replacement rocker arms are readily available from a local parts store or mail-order vendors, modern roller-tip rockers— such as those form Comp Cams or Performance Racing Warehouse (PRW)—install like the stocker units but include a roller tip to lessen the side loading, which causes valveguide wear. Many companies offer full roller rocker arms that use a castalloy or stainless-steel body and combine a roller tip and roller trunion to further reduce friction. At the speed that most street-driven Pontiac engines operate at, there is likely no measurable performance difference in any rocker type, but a roller tip can greatly reduce premature valveguide wear.
High-Ratio Rocker Arms
A popular modification that often increases performance is the use of high-ratio rocker arms. Not only does a high-ratio rocker arm increase gross valve lift, it can simulate the effects of added duration as the valves open and close at a quicker rate. Pontiac used 1.65:1 rocker arms on its R/A-IV to increase gross valve lift from .470 inch to roughly .520 inch. While it may seem easier to simply select a cam that provides the desired amount of lift with 1.5:1 rockers, higher ratio rockers are actually less stressful on the block’s lifter bores because less lobe lift causes less lifter travel.
To achieve a higher ratio, a rocker arm’s pushrod cup is moved closer to its fulcrum. That can change the angle of the pushrod’s path, causing it to contact the pushrod hole that’s machined into the cylinder head. In most instances, the pushrod guide hole can be elongated by using a grinder to gain sufficient clearance. This task must be performed while the cylinder heads are removed from the engine.
An engine’s valvesprings are designed to control valve motion. The valvespring compresses when the valve opens and must keep the valve firmly on its seat when it relaxes. Most Pontiac engines originally used a dual cylindrical spring package. Most aftermarket dualspring packages include an inner and outer spring and an internal damper, which is placed between the springs to minimize coil surge. Springs of this type are available in a wide array of pressure ratings from many manufacturers. They are an excellent choice for street-driven Pontiacs with either flat-tappet or hydraulic roller cams. Most cam companies can suggest the type that works best with a particular grind.
A conical valvespring, or “beehive” spring as it’s often called, features a cylindrically shaped body that tapers as it reaches the top. The shape considerably increases spring rate and reduces the amount of moving mass within the spring, also allowing for the use of a smallerdiameter retainer. The uniquely shaped spring offers increased spring load but reduces the friction generated from added valvetrain mass and component deflection. Though conical springs are quite popular in modern production engines and are an excellent choice for specialized applications, they are not generally required for street-driven Pontiacs.
Measured airflow of an unmodified Pontiac D-port cylinder head, with 2.11-inch intake valves, peaks at approximately 210 cfm at 28 inches of pressure. That amount of airflow should easily support 350 to 400 hp on a larger engine. While that output level may satisfy many owners, there are others seeking to significantly boost performance. That often requires an airflow increase, and that once meant spending hours grinding material from the cylinder head intake and exhaust ports.
When porting cylinder heads, the intent is to improve overall airflow without making the intake port too large, which can negatively affect throttle response and low-speed performance. It entails removing material from areas that restrict airflow while leaving material in areas that otherwise has little effect. A flow bench can be used to measure airflow, or the cylinder heads can be installed on the engine and the performance recorded on the drag strip or engine dyno.
There are now more sensible options than porting your own cylinder heads. SD Performance has created a computerized porting program that can increase intake airflow of a basic cast-iron D-port head to as much as 280 cfm. Additionally, modern aftermarket aluminum castings with the capacity to flow substantially more air than an unmodified original are readily available from a few different sources. Any of these high-quality offerings are available in ready-to-run condition for $2,000 (or less) and should provide plenty of performance for almost any streetdriven Pontiac.
SD Performance has developed proprietary CNC programs for nearly any cast-iron cylinder head that Pontiac produced. The basic package delivers 250 cfm of peak intake airflow and an exhaust-port flow that’s at least 75 percent of that amount. In addition to the beautiful port work, the castings are fully machined and contain top-quality hardware, including 2.11/1.77-inch valves and valvesprings matched for the type of camshaft being used. With a relatively small intake port volume of 165 cc, SD Performance’s CNCported heads can produce up to 500 hp while maintaining good port velocity, which maximizes low-speed street manners.
Kauffman Racing Equipment (KRE) recognized the need for a modern D-port cylinder head for highhorsepower applications. It developed and released its own aluminum casting, which is now available from a number of vendors. Intake port volume is relatively small at 185 cc, which is intended to enhance lowlift airflow, but the casting peaks at approximately 260 cfm in as-cast form. The KRE casting includes 2.11/1.66-inch stainless-steel valves and high-quality valvesprings. A fastburn combustion chamber maximizes combustion efficiency. The KRE D-port head is an excellent value for anyone looking to increase performance.
During the 1990s, Edelbrock created a high-quality cast-aluminum cylinder head for the Pontiac V-8 based on the popular Ram Air IV design. Available in two variations, which are differentiated mostly by their 72-and 87-cc combustion chamber volumes, the casting features an intake port volume of 215 cc and is capable of flowing 280 cfm in as-cast form. Requiring the use of round-port exhaust manifolds or tubular headers, the Edelbrock unit includes 2.11/1.66-inch valves and valvesprings rated to .575-inch lift. The Edelbrock casting is an excellent performance value when compared to original round-port cylinder heads.
Edelbrock has recently released its newest cylinder head for Pontiac V-8 applications, a high-quality Dport. Featuring a reduced intake port volume of 185 cc to improve low-lift airflow, the castings include 2.11/ 1.66-inch valves. Intake airflow peaks somewhere between 250 and 270 cfm.
Many aftermarket companies have produced intake manifolds for the Pontiac V-8 for years. Some of those that produced popular offerings include Doug Nash, Edelbrock, Holley, and Offenhauser. While other modern companies may produce intake manifolds for specific cylinder heads or highly modified applications, Edelbrock has mass produced a wide array of intake manifolds for the Pontiac V-8 longer than any other. Professional Products has recently brought new castings to market.
Edelbrock presently offers at least four different cast-aluminum intake manifolds for the Pontiac V-8. While the others are single-plane designs that require an aftermarket carburetor, the dual-plane Performer and Performer RPM series castings are quite possibly the most popular aftermarket choices available today. The Performer intake manifold is considered a direct-replacement that installs and operates similarly to the factory cast-iron unit in most applications. With the ability to accept OEM emissions equipment, it remains 50-state legal. The main benefit the Performer offers over the stock piece is the weight savings of about 25 pounds.
The Edelbrock Performer RPM intake manifold is a unique dualplane casting that’s designed to improve high-RPM operation without grossly compromising throttle response and low-speed street manners. Though the Performer RPM isn’t as efficient at low speed as the Performer, its relatively deep plenum and long, smoothly contoured runners extend its operating range by several hundred RPM. The deep plenum raises the carburetor flange more than 1 inch over a stock Pontiac unit, however, and that may present hood clearance issues in certain models.
Within the past few years Pacific Performance Racing introduced its Tomahawk intake manifold, which is a modern interpretation of the original Holley Street Dominator, which was last produced in the 1980s. The Tomahawk is a singleplane design. It accepts original and popular aftermarket 4-barrel carburetors and is aimed at increasingthe top-end performance of modified engines. A second manifold, marketed as the Crosswind, is produced by Professional Products. It shares an appearance and operates much like the Edelbrock Performer RPM but lacks an exhaust crossover for cold-weather operation. It may be an alternative when an RPM is considered.
The Rochester 2- and 4-barrel carburetors have been out of regular production since the 1980s, but many remain in good, usable condition. It seems that a Tri-Power setup or single Quadrajet are the carburetors of choice for Pontiac hobbyists. With proper modifications, either can support significant amounts of horsepower. While basic Rochester rebuild kits and certain replacement components can be sourced from local parts stores, only a few companies currently support Rochester carburetor restoration and calibration components.
The Holley 4-barrel carburetor has been around for decades and it was the factory-issued unit on several high-performance Chevrolet applications during the 1960s and early 1970s. The only Pontiac engine to ever specify a Holley 4-barrel was the tunnel-port Ram Air V, but it was never a factory-installed engine on any production vehicle. Several complete engines were assembled and sold through dealership parts departments and Holley produced a limited number of 4-barrels for it.
Over the years a wide variety of new Holley 4-barrel carburetors, with airflow ratings ranging from 650 to 1,000 cfm or more, have been available through the aftermarket. With rebuild and calibration components readily available from most local parts stores or speed shops, the relatively easy tuneability makes Holley carburetors a popular choice for high-performance applications. The square-bore design does not allow for use on any regular-production Pontiac intake manifold, however. An aftermarket intake manifold with a square-bore bolt pattern, such as the Performer or Performer RPM, is required.
Barry Grant offers a complete line of Demon 4-barrel carburetors that function and operate similarly to the Holley. The company also offers an option for Pontiac hobbyists looking for a modern approach to Tri-Power induction. Consisting of a new cast-aluminum intake manifold and a trio of 250-cfm 2-barrel Demon carburetors, the complete kit also includes an air cleaner, linkages and brackets, and all necessary hardware for easy installation on any Pontiac from 1965 and later.
AC Delco produced most of the mechanical fuel pumps found on Pontiac V-8s. Most were application specific and included different fuel line routings, canister sizes, and flow volume and pressure ratings. AC Delco, Airtex Products, and Carter Fuel Delivery Products presently produce stock replacement fuel pumps, and it’s possible that they may be capable of adequately supplying stock-type applications. Significantly increasing engine output might require an aftermarket fuel pump that can supply a greater amount of fuel volume with slightly higher pressure.
Upgrading to an aftermarket electric fuel pump may be the most popular option when an engine’s fuel demand requires additional capacity, but it generally requires significantly modifying the existing fuel lines and adding the appropriate wiring to power its electric motor. Carter, Holley, and RobbMc Performance Products offer popular aftermarket mechanical fuel pumps for Pontiac applications that provide increased fuel capacity while installing relatively easily.
When Pontiac developed its high-performance engine packages, it usually included a unique exhaust manifold aimed at improving exhaust flow. The castings were highly coveted for years because they performed almost as well as tubular headers and were guaranteed to fit the intended Pontiac’s chassis without any clearance issues. These were once worth several hundred to thousands of dollars, depending upon condition.
The originals were cast in grayiron, however, and finding a pair that isn’t warped or cracked can be a very difficult task today. Fortunately for Pontiac hobbyists, a few different companies are casting exact reproductions of a few of Pontiac high-flow exhaust manifolds. The offerings from Ram Air Restoration Enterprises (RARE) are among the best available. They include SD-421 cast headers in iron or aluminum, and long-branch and Ram Air–style manifolds in round-port or D-port versions.
RARE’s manifolds are cast in the same process as Pontiac’s, but RARE uses ductile-65 iron, which is extremely strong and durable. After casting, the ports are cut on a CNC mill to ensure proper configuration and perfect port alignment while the internal runners and collector area are cleaned up by hand. To further improve airflow, RARE can enlarge the collector, which increases airflow 12 to 20 percent over stock and lessens the transition when running larger exhaust pipes. RARE manifolds include a lifetime warranty and can be considered an excellent alternative to tube headers for a street-driven application.
Gaskets and Fasteners
A gasket’s job is to simply seal engine components and prevent outward leaks. Whether it’s keeping coolant within its system or oil from seeping outward, there are a number of task-specific seals and gaskets found within an engine. There are a few different companies producing top-quality gasket sets for Pontiac engines today. Many machine shops and engine builders often use the popular Fel-Pro gasket sets. Fel-Pro gaskets are designed to fit well and provide a long service life. Tin Indian Performance has recently begun offering its own line of gaskets that fit and function similarly.
A rear main seal prevents pressurized oil from escaping through the rear main journal. Modern engines generally use a rubber “lip” seal, but Pontiac used a braided rope seal containing asbestos. The rope seal was packed into a groove that was machined into the block and rear main cap. If installed correctly, it was quite effective and rarely leaked. The asbestos was eventually replaced with a fiberglass material because of government legislation, and it made installation difficult and leaks common.
BOP Engineering developed a direct-replacement lip-type seal specifically for the Pontiac V-8. It is Constructed of Viton, popular with hobbyists, and I’ve successfully used it in my own engines. Tin Indian Performance offers a similar and reportedly successful unit. Best Gasket Company now offers a stock-type rope seal constructed of braided graphite that fits and installs just as Pontiac’s original seal. Many users report excellent results. Confer with your Pontiac vendor about which seal may work best for your application.
A fastener’s clamping force can be compromised if reused a number of times and even the most capable fastener can be ruined the moment too much torque is applied. ARP is an industry-leading fastener manufacturer. It produces a complete line of high-quality, bolts, nuts, and studs, and offers many part numbers specific to Pontiac applications. ARP is the best choice when new fasteners are needed for any portion of a project.
Written by Rocky Rotella and Posted with Permission of CarTechBooks
GET A DEAL ON THIS BOOK!
If you liked this article you will LOVE the full book. Click the button below and we will send you an exclusive deal on this book.