In the long history of the Gen I small block Chevy, there are a couple of high-water marks most everyone knows about. The first was the 375 horsepower, fuel injected 327 found in the 1964 Corvette. The second and more highly sought after small block is the 1970 350ci LT1 engine used in the Corvette and Camaro.

The LT1 came from the factory with 11:1 compression, a solid lifter camshaft, iron cylinder heads, and a 750 cfm Holley carburetor on an aluminum dual plane intake manifold. The LT1 was rated at 370 horsepower in the Corvette and 360 horsepower in the Camaro. Can’t be upstaging our halo car, can we?

We thought it might be fun to build a small block that would visually replicate an LT1 while adding some modern muscle. We settled on doing a 383ci stroker.

Story Overview

  • Jeff Smith shows you how to build a 383ci small block Chevy stroker engine that looks like a 1970-vintage LT1 350
  • This engine is the first stage of a two-stage build. Stage II will have Trick Flow cylinder heads, a roller camshaft, and other big power upgrades
  • Learn why aligning the lifter bores with the camshaft tunnel can reduce cam wear
  • See a complete parts list for this engine build

This build was done in two stages. Stage 1 used factory LT1 external parts, a forged rotating assembly, and a replica of the LT1 mechanical camshaft. Stage II would dispense with the LT1 disguise and add Trick Flow DHS200 aluminum heads, a Summit Racing Pro hydraulic roller camshaft with the GM LS firing order, and a single plane intake manifold in the quest for big horsepower.

We got Summit Racing to join us in this little engine conspiracy. They supplied the rotating assembly, cams and valvetrain, and other parts needed to build the 383. Our long-time pal Chuck Hanson in Tennessee helped us dredge up a set of 1971 #492 cylinder head castings along with the proper aluminum intake manifold, valve covers, distributor, and Holley carburetor for the Stage 1 build.

Oops, Wrong Block

Right off, we have to confess that we muffed the plan a bit. Our friend Ron Flood, owner of Cedar Machine, had a block for sale that appeared to fit our requirements. He had fully machined this block by align honing the mains; boring the cam galley to make the camshaft parallel with the mains; adding larger 0.875-inch lifter bore bushings; and blueprinting the block to GM specs.

All that looked great, so we bought the block—only to discover that it was a later two-piece rear main seal casting with the passenger side dipstick. The proper block for an LT1 would have a driver side dipstick. We were too far along to go looking for another block, so we used the one we had.

Rotating Assembly

The rotating assembly features a 3.75-inch stroke Summit Racing 4340 forged steel crank, a set of 6.00-inch Summit Racing H-beam connecting rods, and Summit Racing 2618 alloy forged pistons. The piston has what amounts to a 9cc dish that will work with the 64cc iron heads as well as the TFS DHC heads we plan to test in the Stage II build. The compression with these pistons and heads comes out to right at 10.5:1, which should be just on the safe side with 91 pump gas.

The first order of business was to establish operating clearances for the rod and main bearings along with checking the crankshaft endplay. Using Clevite coated bearings, the rod and main clearances all came in around 0.0025-inch with some minor variations. The crank endplay measured 0.004-inch.

Short Block Assembly

Before we assembled the engine, we wanted to ensure that there was sufficient piston-to-valve clearance with the Summit Racing roller cam we’re using in the Stage II build. We installed a piston in cylinder Number One, the roller cam, and a cylinder head with checking springs. We used the dial indicator to accurately measure the clearance at 10 degrees before and after Top Dead Center where clearances are the tightest. With 0.140-inch or more of clearance on both valves, we won’t have any clearance issues.

After final washing the block and rotating assembly parts, we started putting the engine together. We installed a Summit Racing GPX ring package on the pistons, then slid the piston/rod assemblies into the cylinder bores using a Summit Racing tapered ring compressor and hand pressure. With all eight pistons in place, we used our ARP rod bolt stretch gauge to set bolt stretch to the ARP spec of 0.0050-inch.

Normally we would have installed the camshaft before the rotating assembly to ensure there was no binding on the cam bearings. Since we had already used the Summit Racing roller cam to check piston-to-valve clearance and found no bearing issues, we slid the Summit Racing LT1 muscle car cam in the block.

Why Bigger Lifter Bores?

Since the block was machined for larger diameter 0.875-inch lifters, we used—dare we say it—Ford hydraulic flat tappet lifters.

Here’s why: Factory blocks often have lifter bores that are not properly aligned to the camshaft tunnel. This is usually due to machining errors or core shift during the casting process. The misalignment will not allow the lifters to rotate, which leads to excessive lifter and cam lobe wear or outright failure.

That was the case with our block. Cedar Machine fixed the issue by enlarging the lifter bores and insert bushings to accommodate the Ford lifters. You can bush the bores to use standard 0.842-inch Chevy lifters, but using the larger Ford lifters puts a little more lifter face on the cam lobe. That reduces unit loading pressure on the lifter and camshaft, reducing wear.

There’s no real performance advantage to going with the larger lifter diameter for flat tappet cams—we did it for durability reasons.

The Rest

While checking oil pump to oil pan clearance, we discovered the windage tray we planned to use would not work with the stock pan. So, we went without it.

We pre-assembled the #492 iron cylinder heads with new guides, valves, factory-style valve springs, and seals. We also had a valve job performed. We sacrificed a tiny bit of authenticity by using ARP head bolts in place of factory-appearing bolts. We’ve had problems in the past with minimal factory head bolt thread overlap in older blocks and didn’t want to pull any threads out of our block. We won’t have that issue with the ARPs.

The rocker arms are 1.6 ratio COMP Cams Pro Magnum rollers. The chromoly rocker arms have less mass in non-critical areas and more beef in areas that take the most punishment. That makes the rockers five percent lighter at the valve than comparable aluminum rockers.

With the heads torqued and sealed, we bolted on the factory dual-plane intake manifold. Some mild tweaking was required to make it fit correctly. We also converted an original LT1 distributor over to a Pertronix kit to eliminate the old-school points.

We filled the 383 with five quarts of Driven Racing BR30 break-in oil and used our ancient but trustworthy engine priming tool to pressure lube the engine. We set the harmonic balancer to 15 degrees Before Top Dead Center for the 383’s initial timing, then dropped the distributor in place and tightened it down.

We bolted an original OEM Holley 780 CFM carb on the engine for the photos of our small-block subterfuge. We used a 750 CFM Holley 3310 carburetor for testing. After a quick session on our Summit test stand to ensure the engine was ready for the dyno, we headed out to our local facility in Waterloo, Iowa.

In Part 2 of our story, we’ll dyno the Stage I build, then do our Stage II upgrades and dyno that combination. Stick with us–it’s going to be fun!

Stage I Short Block Parts List

Summit Racing™ Forged Crankshaft SUM-SBC35037502P
Summit Racing™ Performance SBC Forged H-Beam Connecting Rods SUM-SBC60002H         
Summit Racing™ Forged Pro Pistons SUM-SBC383030L         
Summit Racing™ Pro GPX Gas Ported Piston Rings SUM-GP403012
Clevite H-Series Coated Main Bearings CLE-MS909HC                          
Clevite H-Series Coated Rod Bearings, standard CLE-CB663HNC                                         
Melling Shark Tooth Oil Pump, high pressure/standard volume MEL-10553ST                          
Dorman Replacement Oil Pan, passenger side dipstick RNB-264103                            
ARP Main Stud Kit ARP-234-5610                      
ARP Oil Pump Stud ARP-230-7003                    
Fel-Pro Performance Rear Main Seal FEL-2912                         
Fel-Pro Performance Oil Pan Gasket FEL-1880                          
Summit Racing™ Freeze Plug Kit SUM-1581

Stage I Camshaft and Valvetrain Parts List

Summit Racing™ Muscle Car Replacement Cam, LT1 SUM-1124
COMP Cams High Energy Hydraulic Lifters for Ford CCA-832-16
Melling Double Roller Timing Set MEL-40400
COMP Cams Pro Magnum Roller Rocker Arms CCA-1605-8
COMP Cams Magnum Pushrods, 5/16″/7.800″ CCA-7372-16            
ARP High Performance Cylinder Head Bolts ARP-134-3601                 
Fel-Pro Performance MLS Head Gaskets FEL-1142

Stage I External Accessories Parts List

Carter Muscle Car Mechanical Fuel Pump CRT-M6624                                       
Summit Racing™ OEM Style Harmonic Balancer SUM-161358           
Summit Racing™ Harmonic Balancer Bolt SUM-G1677
Dayco Mechanical Water Pump DAC-DP1003                           
Summit Racing™ Crank Pulley, 2-groove SUM-G3957B          
Goodmark Alternator Bracket GMK-4012285691S
Classic Performance Water Pump Pulley, 2-groove CLP-CP38813     
Auto Metal Direct Air Cleaner Assembly AMD-W-460

Stage I Misc. Parts List

Fel-Pro R.A.C.E  Gasket Set FEL-2702               
Fel-Pro Performance Intake Gaskets FEL-1266                                        
Fel-Pro Water Neck Gasket FEL-2202
Fel-Pro Performance Header Gaskets FEL-1405                        
ARP Fuel Pump Pushrod ARP-134-8701                                                                   
Pertronix Ignitor II Solid State Ignition Conversion PNX-91181                        
Summit Racing™ Oil Filter Adapter SES-3-60-08-900
Driven Racing GP-1 Break-In Oil, 6 quarts JGR-19336-6                        
Driven Racing GP-1 10W30 Engine Oil, 6 quarts JGR-19306-6

Chevy 350ci engine block being machined
We based our LT1-disguised 383ci build on a fully machined block. Rod Flood at Cedar Machine blueprinted our block, paying special attention to the cam bore to ensure it was parallel to the main bore centerline. Rod also offset-bored the cylinders to maximize cylinder wall thickness. The work necessary to accomplish this is expensive but we felt the engine warranted the investment. The block in this photo is for a different engine, but it’s representative of ours. (Image/Jeff Smith)
Summit Racing Forged Crankshaft for small block Chevy
We began assembly with a 3.75-inch stroke Summit Racing forged crankshaft fitted with Clevite H-Series main and rod bearings. The bearings have a moly/graphite treatment to reduce friction. Previous testing by our friend Lake Speed, Jr. at Driven Racing revealed that a combination of coated bearings and synthetic oil is a great way to minimize wear and extend engine life. (Image/Jeff Smith)
Measuring main journal clearances on a Summit Racing Forged Crankshaft
We calibrated our micrometers to properly measure main and rod bearing clearances. For a high-performance street or race engine, you really can’t rely on that green wax string (aka Plastigage) to establish clearances. The right way takes time but it’s far more accurate. (Image/Jeff Smith)
Checking main bearing clearances on a small block Chevy
We measured the main journal diameters in the block as well to establish the actual main bearing clearances. Thanks to precision machining, we had almost exactly 0.0025-inch of clearance for all five mains. (Image/Jeff Smith)
Measuring crankshaft endplay on a small block Chevy
We also measured crank endplay to make sure there was plenty of clearance for the thrust surface between the crank and the Number Five main bearing. Clearance came out at 0.004-inch, right where we needed it to be. (Image/Jeff Smith)
Summit Racing H-beam connecting rods and forged pistons for a 383ci small block Chevy
A set of 6-inch long Summit Racing H-beam connecting rods and forged pistons round out the rotating assembly. The combination of cylinder heads with 64cc combustion chambers and a 3.75-inch stroke required pistons with a 9cc dish. The deep valve reliefs will provide the piston-to-valve clearance required for the larger roller cam we have planned for the second stage of this build. (Image/Jeff Smith)
Installing piston rings on a forged piston for a small block Chevy
The pistons are machined for use with a Summit Racing GPX gas-ported ring package. The combination of thin 1.2mm/1.2mm/3mm rings and the gas-ported top ring will provide a better seal in the cylinder bores. That should help keep a little more cylinder pressure in the cylinders and thus improve power.(Image/Jeff Smith)
Installing piston and connecting rod assembly in a small block Chevy
The thinner ring package made it easier to push the piston/rod assemblies in the bores. All we needed was a Summit Racing tapered ring compressor and some gentle finger pressure. (Image/Jeff Smith)
Measuring connecting rod bolt stretch for a small block Chevy
The connecting rods are held together with ARP 2000 rod bolts rated at 220,000 PSI of tensile strength. We measured rod bolt stretch with this ARP digital stretch gauge. Rod bolts are designed to stretch a specified length when torqued. This ensures the bolts will apply the proper clamp load to keep the rod together. Our ARP bolts required 0.0050-inch of stretch. (Image/Jeff Smith)
Rotating assembly installed in a small block Chevy
Here’s the rotating assembly in place. The main caps retained by a set of ARP main cap studs. You’ll notice the studs are longer for use with a windage tray. We tried to fit a factory windage tray, but the Dorman OE replacement oil pan wouldn’t cooperate. We’ll use a kickout style oil pan with a full windage tray for the Stage II build. We also installed a Melling Shark Tooth standard volume/high pressure oil pump and matching pickup. (Image/Jeff Smith)
Installing a camshaft in a small block Chevy
The Summit Racing Muscle Car camshaft is patterned after the 370HP/327 solid flat tappet cam used in the 1970-71 LT1 (GM #3972178). Here are the specs:
Advertised Duration: 295°/308°
Duration at .050″ Lift: 242°/254°
Lift with 1.5 Rocker Arm: .459″/.485″
Lobe Separation: 116°
Valve Lash: .020″/.025″
.875-inch lifter bores with bronze bushings in a small block Chevy
Our block had the lifter bores machined oversize and fitted with bronze bushings to accommodate 0.875-inch Ford hydraulic flat tappet lifters. This was done to correct lifter bore-to-camshaft alignment that can cause excessive wear or outright cam and lifter failure. The larger Ford lifters also reduce unit loading pressure on the lifter and camshaft to further extend their lifespan. (Image/Jeff Smith)
Degreeing camshaft in a small block Chevy
We used our COMP Cams Pro degree wheel to dial in the cam. We found the intake centerline to be within a half degree of its proper place. You can tell I’ve had this wheel for awhile by the red anodizing. Current ones are blue. (Image/Jeff Smith)
Checking valve spring height in a small block Chevy
We used stock valve springs in the #492 cast iron heads to minimize the load when we break in the solid lifter cam. We also checked coil bind and retainer-to-seal clearance to make sure the valvetrain would accommodate the cam’s lift. Measured height was 0.494-inch, just a little shy of the .050-inch minimum clearance required for our cam.
COMP Cams roller rocker arms in a small block Chevy
We torqued the heads in place, checked for proper pushrod length, and then lashed the valves to 0.020-inch intake/0.025-inch exhaust specifications as indicated on the cam card. We will recheck the lash after the engine has warmed up on the dyno. We also fitted a set of 1.6 ratio COMP Cams Pro Magnum steel roller rocker arms. (Image/Jeff Smith)
383ci small block Chevy on engine stand
Here’s our faux LT1 with the stock iron heads, the correct 1970 GM “snowflake” intake manifold, a 3310-style 780 CFM Holley vacuum secondary carburetor. We also scrounged up a set of the vintage Corvette valve covers. The factory points distributor got a Pertronix Ignitor II electronic conversion. (Image/Jeff Smith)
Keywords
engine build , small block Chevrolet
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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.