Engine-build primers are a main component of the technical aspect of HPP. We pride ourselves on furnishing the readership with detailed information that can be used on their Pontiacs. We've covered the gamut from a basic engine freshening to all-out drag-race powerplants and everything else in between. This time, however, we're doing something different.
We went to Jim Taylor Engine Service (JTES), a well-respected Pontiac shop, to document the freshening and modifying of a 455 for a customer, Bill Wise from Queens, New York. His '74 LeMans is a street/strip car that features a rollcage, a complex stereo system, and other accoutrements. The Pontiac weighs approximately 4,300 pounds and is driven everywhere it goes. The previously Taylor-built engine was strong-proven by numerous 12.54 timeslips-and reliable, with more than 10,000 problem-free miles of street/strip service.
But Bill wanted more-an 11 second e.t. was the goal, and Jim Taylor Engine Service believed it could accomplish that.
The trick is to achieve the customer's goals, despite the heavy race weight and without sacrificing the street driveability of the Pontiac or adding nitrous. That means engine vacuum must be good; only straight pump gas exits the carburetor boosters; and it has to do everything a stocker does-just go a lot faster.
Over the years, the term street car has become skewed, since to many magazines it means a license plate, windshield wipers, and a rearview mirror. HPP's definition of a street car is one that can start in all weather, sit in bumper-to-bumper traffic and idle, and the key can be tossed to anyone with a driver's license with no concern for hurting the engine. It also has to be impressively quick-a tall task for a Pontiac that weighs more than two tons.
The traditional means of making easy power-raising the compression ratio, and installing a larger (more aggressive) camshaft-isn't acceptable since it diminishes the car's streetability. Thus, Jim Taylor Engine Service needed to further dial-in the already refined 455. This meant an all-out attack on the minute details of the engine.
When building and blueprinting an engine, there are higher levels of tolerance. Extreme attention to detail is nice, but as with anything, a cost/benefit ratio needs to be established. For example, when porting a cylinder head, you can spend 100 extra hours and only pick up a few cfm, which may yield 10 hp. The standard protocol would be not to invest that amount of time because you don't need it. But instead do a good street port and look for the power elsewhere, such as in the cam or compression ratio. The customer has a good product within his budget and everyone is happy.
In contrast, the world of NHRA Stock and Super Stock Eliminator engine building takes the exact opposite approach. Since the rules limit the modifications, every last detail of the engine needs to be machined and assembled to perfection. [A task that takes a huge investment in time and knowledge but allows the relatively large number of stock parts to produce more power than what the factory did.] Though not a Super Stock engine, JTES applied many of the same edicts to this Pontiac, which makes it a unique educational experience for our readers.
Due to the nature of the rebuild, we chose to skip the traditional photos of the crankshaft being dropped in or the assembly of the cylinder heads and other parts. Instead, we spent three days documenting some of the exacting procedures employed on this engine.
The engine-block water passages were partially filled with Rokblock. This is done not only
After mixing, Rokblock was poured into the engine through the rear core plug and the front
The stock 4.210-inch stroke nodular-iron crank was retained, as were the Crower connecting
Piston skirts and crowns were coated by Swain Technology. The thermal barrier on the top h
The pistons use a full-floating pin that is held in place by a spring steel lock. Floating
Attention was paid to the piston-ring end gaps (second ring shown)-they were carefully cre
What's interesting is that other than the consumables (rings, bearings, gaskets) only the intake was changed. The 6X cylinder heads were treated to a precise porting on the intake side to increase flow from 230 cfm (the previous porting) to 255 cfm at 0.550 inch. The additional power was sought in a few other areas beyond the cylinder-head intake port: the installed position of the camshaft and a swap to a port-matched Torker II from a worked Holley Dominator and its precise alignment with the cylinder heads. The cam, which was ground 6 degrees advanced, was installed straight-up for the first build. For this one, it was retarded 4 degrees. The other work was based on producing exacting dimensions and meticulous assembly by Mark Erney.
Extreme attention to detail is sometimes overlooked on a Pontiac engine build, but as we hope to prove in Part II of this primer when we test on the dyno, it's an effort worth taking.
All eight sides of the ring gaps were dressed with a 320-grit polishing stone to remove an
A dial indicator is used to find TDC; then it's pivoted to the deck. The difference in the
JTES retained the same Crane mechanical roller cam with 252/256-degrees duration at 0.050,
With the timing chain and gears installed, a special tool is fitted in through the lifter
The dial-indicator tool rides directly on the cam lobe, as seen here (there are tips for f
JTES used a degree wheel and a specially mounted board as a reference instead of a wire po
Needle-nose pliers were used to check the clearance and amount of endplay of the oil pump.
An insulator to absorb vibration (essential with a mechanical camshaft) and to eliminate w
With the windage tray leveled, the dipstick was marked for the full level with the 8-quart
The oil-pump pickup level was also checked in relation to the sump of the pan.
To ensure its mooring, the two-piece dipstick tube was staked together.
A restrictor was used to limit the oil supply to the valve lifter, and in turn, the rocker
The oil restrictors were placed in the lifter bores on the intake side for a street applic
The 6X cylinder heads had been previously ported to flow 230-cfm intake. For this build, t
It's important to check the length of the cylinder-head bolts before installation. If the
Before the cylinder heads were installed, the block deck surface was cleaned with lacquer
JTES has a unique approach with intake-manifold fit. Jim Taylor and Mark Erney recognize t
With the water removed from the air portion of the intake manifold, it was shifted for opt
Using a vernier caliper, precise measurements were taken of the wall between the ports and
A great deal of attention was paid to the port match of the gasket.
The manifold was trial-fitted many times and located properly. Often it's necessary to mil
|High Performance Pontiac Engine Buildup Worksheet|
|Block/Crank Combo||Factory 455|
|Block Description||'73 455|
|Preparation||Clean and Magnaflux; install four-bolt main caps from Program Engineering; align-bore and set thrust, bore, hone, deck; tap lifter feeds for oil restrictors; deflash lifter valley|
|Crank||'70-'73 Pontiac nodular-iron|
|Preparation||Reground, micro-polish, deflash, balance w/complete assembly|
|Rods||Crower Sportsman forged-steel|
|Preparation||Check, measure big end and pin end|
|Bearings||Sealed Power H.D.|
|Preparation||Cleaned with 0000 steel wool and washed|
|Pistons||JE/SRP forged, flat-top with valve reliefs|
|Preparation||Coated by Swain Coatings, ceramic top and dry film sides|
|Piston to Deck Height||-0.005-in|
|Piston Pins||JE full-floating|
|Method Used to Retain Piston Pins in Pistons||Double spiral locks, included with pistons|
|Rings||Total Seal TS1 gapless, low-tension oil rings (14-pound pull)|
|Preparation||Set gaps 0.019-in top and second|
|Rod Bolts/Head Bolts||Crower connecting rod bolts, ARP head bolts|
|Balancing||By Hoffman Machine|
|Windage Tray||Pontiac 455|
|Oil Pan||Moroso 8-qt |
|Oil Pump||Mellings M54D, Moroso pickup|
|Preparation ||Disassemble, wash, clearance check, make custom oil-pump pickup retainer plate, reassemble|
|Casting Number ||6X|
|Combustion-Chamber Volume ||90cc|
|Maximum Flow at 28 inches of water|
| Intake ||255 at 0.550-in|
| Exhaust||180 at 0.550-in|
|Compression Ratio ||9.6:1|
|Valves ||Ferrea SS|
|Angles Used in Valve Job ||Original 30- to 65-deg int, 45-deg exh|
|Retainers ||Comp Cams titanium|
|Keepers ||Crower jumbo locks, 10-deg, w/lash caps|
|Valveguides ||K-Line liners|
|Valve Seals ||Corteco, all Teflon|
|Rocker Studs ||ARP Pro series 2-in |
|Rocker Arms ||Crower full-roller|
|Rocker Arm Ratio ||1.6:1 intake/1.5:1 exhaust|
|Pushrods ||Smith Bros. seamless chromoly 0.083-in wall|
|Duration at 0.050||252/256-deg|
|Lift||0.598/0.560 gross, 0.578/0.540 net |
|Lobe Separation Angle||112-deg|
|Installed Position||Degreed to cam card by retarding 4-deg|
|Seat Pressure||165 psi|
|Open Pressure||425 psi|
|Timing Chain||Rollmaster -0.002-in|
|Type ||Double roller, prestreched|
|Carb||Holley 4781 w/Wilson 1-in tapered spacer (Demon shown in photo)|
|Mods||Rejetted, added notched rear float and jet extensions|
|Intake Manifold||Torker II single-plane|
|Distributor||MSD Pro Billet|
|Coil||MSD Blaster 2|
|Headers||Hooker (for the dyno)|
All engines are hot-run on a test stand before going to the dyno facility or being shipped
The manifold underwent a trial fit with a feeler gauge confirming contact with the gasket.
A stud girdle supplies support and limits deflection in the valvetrain. This is extra insu