Well, it didn't take much to talk me into a HT-383 as the powerplant for my hot rod '53 GMC. At this point, plans call for a 4L80E, a 3.50:1 ratio 9-inch rearend (sorry guys), a 750-cfm Holley, Patriot headers, and a PerTronix electronic distributor. I figure this combination will be perfect for a classic truck that'll spend as much time haulin' parts as it does haulin' butt. Read on and check out the guts that give this crate engine its grunt.
On a recent trip to the Street Rod & Performance Trade Show in Indy, I was lucky enough to cross paths with Gary Penn, a Performance Parts product specialist from General Motors Special Parts Operations. I say lucky for a few reasons. First, he's a heck of a nice guy; second, he's extremely knowledgeable; and third, because at that time I was gathering the parts and components for yet another classic pickup project. Up until that day I'd been agonizing over what powerplant to choose as the heart of my ride, everything from a 292ci inline-six to a 502 big-block, and practically everything in between. That is, nearly everything, but Gary's immediate choice--a logical and, what may well be one of the most cost effective powerplants available for classic truck applications--the GM HT-383 Stroker.
According to Gary, the HT-383 (PN 12497317) was basically the result of a quest by GM Performance's Ernie Callard, who at the time was a project manager, who'd been given the task of developing a replacement engine for late-model trucks. GM was looking for an engine that'd be just the ticket for anyone who was looking to replace a tired, old truck motor with a fresh unit. One that'd be up to the task of hauling a workday payload or, just as easily, a boat, racecar, or a travel trailer. In order for this engine to be a no-hassle bolt-in, it'd naturally have to be a small-block, but one with a hefty amount of low-end torque. Well, what the gang decided on was a 383-cube stroker that would have the torque of a big-block. They also figured that in order to keep the engines affordable, they'd have to comprise it of off-the-shelf parts.
Well, they did it (not that I had any doubts, mind you), they whipped together a package that's been specially tuned for torque--and at a price that won't break the bank (How's under four grand grab ya?). The HT-383 ended up delivering great truck power in a small-block package. With its 3.80-inch stroke and Vortec cylinder heads, the 383 makes awesome torque (for pulling a load or just smokin' the tires). Peak torque is 415 lbs-ft at 3,500 rpm, but the HT-383 even makes over 400 lbs-ft between 2,500 and 4,000 rpm! Developed as a truck engine, with a truck grind roller cam, heavy-duty forged powdered metal connecting rods, forged crankshaft, and hypereutectic pistons, the HT-383 is designed to be worked, and 325 hp at 4,500 rpm doesn't hurt either. According to GM, the HT-383 should only be used in '73-and-earlier pre-emissions vehicles--heck, sounds like it was meant for classic trucks. Don't ya think?
The backbone of the HT-383 assembly ended up being an '86-99, 4-inch bore, Gen-1, heavy-duty four-bolt main-block (PN 10105123). | 
The blocks are machined for one-piece rear crank seals, and they weigh in at 197 pounds. The cylinder wall thickness is the same as current production engines, and the lifter valleys are machined for a hydraulic roller and flat tappets. The blocks will also accept cranks that have a two-piece seals with the addition of an adapter (PN 1005118). | 
Speaking of cranks. The crankshaft chosen for use with this block is a forged unit manufactured of 4340 steel and has a 3.800-inch stoke (PN 12489436). |
This small-block connecting rod is used in HT-383 crate engines. This steel powdered metal (PM) connecting rod is 5.7-inches long from the center of the crankshaft hole to the center of the piston-pin hole. The rod is machined to clear the camshaft in most small-block stroked-type engines and is equipped with screw-in studs rather than bolts. This connecting rod was tested for 45 hours in a 550hp engine assembly at 6,000 rpm. | 
HT-383 pistons (PN 12489437) are high-silicon aluminum (hypereutectic) and are fitted with a pressed pin. It's a high-performance piston that has a 10:1 compression ratio with 62cc head chamber volume. | 
This hydraulic roller design cam is used in the HT-383. The duration at lash point in degrees (intake/exhaust) is 288/308; duration at .050 lift (intake/exhaust) is 196/206; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 431/451. Valve lash is zero/zero and lobe centerline is 109-degrees (PN 14097395, cam only). Note: Shown with non-standard roller rockers and components. |
The 383-stroker is outfitted with one of America's favorite high-performance cast-iron small-block cylinder head. The Vortec cylinder head's fast-burn combustion chamber and high-velocity ports combine to produce big horsepower out of the box. The Vortec head can be mildly ported for additional performance and can be milled up to .040 for increased compression ratio. The Vortec head uses 1.94 intake valves and 1.50 exhaust valves to complement the high-velocity port design. The Vortec head out flows the BowTie head out of the box and is a 20-40 horsepower bolt on increase over earlier cast-iron small-block heads. Plus, Vortec heads (PN 12558060) fit all small-block engines produced from '55 to present (excluding LT1/LT4 reverse coolant flow engines and current LS1 style engines). If purchased separately, they come completely assembled with valves, springs, retainers, and 3/8-inch rocker studs, but require the use of self-aligning stamped-steel rocker arms. | 
Technical Notes: The maximum camshaft lift is .475. The valve seats in these heads can be machined to 2.02 intake and 1.60 exhaust. The rocker arm studs can be pinned or drilled, and tapped 3/8-inch. | 
Spanning those awesome Vortec heads is a Vortec manifold (PN 12496820) that's been designed for ultimate horsepower and torque when used in conjunction with Vortec cylinder heads. This aluminum four-barrel manifold will accept Holley or Quadrajet carburetors and is EGR equipped. |
Being that the HT-383 was designed primarily as a hot replacement engine, they aren't really dressed for show. However, this can easily be rectified by the addition of a few GM accessories. I've chosen to add a set of nice looking aluminum valve covers to dress mine up just a bit. These cast-aluminum Bow Tie design valve covers (PN 12480127) are a short-style design and come with a PVC hole in both covers. They are sold two per box and include rubber grommets. The adapters (PN 24502540) are used to bolt the flange-mount valve covers shown to the HT-383 or any '87 and up center-bolt style engines. | 
Technical Note: These adapters are CNC-machined from billet aluminum stock and include two adapters and fasteners. The replacement O-ring gasket is PN 12480023. | 
Another item that I chose to use (and would suggest to anyone using a small-block GM crate engine) is GM's small-block serpentine drive system.
This deluxe serpentine belt-drive system with air conditioner includes all the components needed to outfit the HT-383 with all the engine's pertinent accessori |
So there you have it, details on what is perhaps one of the most ideal replacement crate engines you (or I) could ever slide into the engine bay of a classic truck. Stay tuned for updates on my hot rod '53 in the future, and I'll let you know what I think about my stroker motor when I get a few miles under my belt. | | |
The bolts, nuts, spacers, and braces are included with the following major items:
10055800 Secondary Air Injector pump bracket
1134344 Air compressor assembly, (CR4)
10129569 Idler belt pulley bracket
88894005 Water pump kit
10055880 Water pump pulley
10055879 Crankshaft pulley
10463172 Generator assembly (remanufactured)
12117361 Generator connector (with lead)
10055798 Drivebelt Tensioner Assembly
10085752 Belt (fan, water pump, A/C pump, and generator)
10105212 Generator & power steering bracket
26010328 Power steering pump
14102096 Power steering pulley