The Case for a Crate Engine

Why a Substitute for That ’60s Small-Block Makes Sense

By Ron Ceridono   –   Photography by the Author

There are those among us who were building and driving modified Chevrolets in the ’60s; many of us have a similar affliction as a result—a severe case of selective memory. While sound and feel of a high-winding small-block hooked to a four-speed transmission was impressive in the good old days, the fact is many contemporary front-drive family cars will suck the headlights out of the cars we still hold near and dear to our hearts. Fond memories are often the result of “The older I get the faster I was” syndrome.

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002 right side dipstick and center bolt PML Corvette style rocker covers
There are some obvious tells that this is a Gen II small-block: The right-side dipstick and center-bolt PML Corvette-style rocker covers are giveaways.

Besides the performance deficit that is a painful reality, many of the performance engines from those bygone days have other shortcomings as well; the 300hp 327 in our ’63 Corvette is a prime example. Back in the day of “high-octane” gas, the 10.5:1 compression and iron heads weren’t a problem, but with today’s fuel, engine-killing detonation can be an issue. In addition, unleaded fuel can cause valve and valve seat wear issues, so arguably the sensible idea is an engine swap.

003 weighted 153 tooth flexplate
Gen II engines are externally balanced. Ours came with a weighted 153-tooth flexplate. The arrow points to the balance weight (arrow).

More Engine Goodness: My First 383 Part 1: The Short-Block

In the age of Chevrolet’s revolutionary LS engines one has to wonder why anyone would choose to repower a vintage car with anything else. But then there are those diehards among us, so we decided on a Chevrolet Performance Gen II small-block because an LS just wouldn’t look right (address all hate mail directly to ACP editor Nick Licata). When it comes to selecting a Chevrolet crate engine, Gandrud Chevrolet has a variety in stock that range from mild-mannered drivers to asphalt shredders. Ours is the SP350/385, the 350ci version that generates 385 hp with 405 lb-ft of torque—that’s 85 more horsepower and 45 more lb-ft of torque than the original 327.

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004 Centerforce billet aluminum flywheel
As we would be using a manual transmission, we installed a Centerforce billet aluminum flywheel. Note the balance weights (arrows) and the mechanically retained ring gear (bolt-on rather than press fit).

While we aren’t trying to fool anyone, one of our goals for this swap was to maintain the spirit of the original engine, if not the exact appearance. Interestingly, our new engine came with heads that were drilled for the late-style eight-bolt intake manifold as well as the early 12-bolt style. However, while the boltholes line up, our early cast-iron manifold did not match the ports in the new heads. To solve the intake manifold dilemma, we simply used the new aluminum manifold, which did require redrilling the Carter AFB carburetor we’ve had on the shelf since 1977 (proof that you should never get rid of any car parts). However, using the late manifold meant that we no longer had a way to put oil in the engine or introduce fresh air into the engine for the positive crankcase ventilation (PCV) system.

005 Centerforce flywheel features a replaceable heat treated friction surface
The Centerforce flywheel features a replaceable, heat-treated friction surface. The flywheel bolts are from ARP.

In addition, the intake manifold attachment points on the new heads are also drilled for late-style center-bolt rocker covers as well as the earlier perimeter bolt design. Again, the boltholes line up, but the pushrod ends of the rocker arms hit the insides of our cool new reproduction covers from Classic Industries. The solution to that was a set of cast-aluminum, Corvette-style rocker covers from PML. Along with solving our rocker arm clearance issues, holes were provided in each cover for the PCV system. Additionally, now oil can simply be added to the engine through one of the grommet holes with a flexible funnel PML provides.

006 pilot bushing or bearing must be installed in the crankshaft to support the input shaft of a manual transmission
A small but important part, a pilot bushing or bearing must be installed in the crankshaft to support the input shaft of a manual transmission.

Give it the gas: Updating a Second-Gen Camaro Fuel System for LS Power

The final touch on our engine swap was to add the original ignition shielding; like most Corvettes, ours used a variety of brackets to mount them. Two for the ignition shield brackets and the one for the fuel filter were originally secured by the original intake manifold bolts, which we no longer had. To address that issue, we used a new intake manifold gasket with both manifold bolt patterns (Fel-Pro 1255) and drilled the necessary holes in the manifold and installed studs.

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007 aluminum fast burn heads that feature D shaped exhaust ports and angled spark plugs
Our SP 350/385 came with aluminum fast-burn heads that feature D-shaped exhaust ports and angled spark plugs.

Our substitute small-block checks all the boxes on the list of attributes we were looking for. We wanted a modest increase in horsepower and torque, an engine that would run on today’s fuel, and not look out of place when we opened the hood. We got all that and a 24-month or 50,000-mile limited warranty. The good old days just got better.

008 mismatch between the reproduction
The D-port exhaust gasket showed there was a mismatch between the reproduction, early style ram’s horn exhaust manifolds and the ports in the heads.

[Side bar ]

SP SP350/385 specs:

Displacement (ci): 350
Bore x Stroke (in): 4.000 x 3.480
Block: Cast-iron with four-bolt main caps
Crankshaft: Forged steel (shot peened)
Connecting Rods: Powdered metal
Pistons: Hypereutectic aluminum
Camshaft Type: Hydraulic roller
Camshaft Lift (in): 0.474 intake /0.510 exhaust
Camshaft Duration (at 0.050 in): 208 degrees intake/221 degrees exhaust
Cylinder Heads: Fast Burn aluminum; 62cc chambers
Valve Size (in): 2.000 intake/1.550 exhaust
Compression Ratio: 9.6:1 nominal
Rear main seal: One piece

009 port matching the manifolds to the heads made us feel better
It might not make much difference in performance, but port-matching the manifolds to the heads made us feel better.

[Side bar 2]

Positive crankcase ventilation (PCV) systems provide two important functions—it draws contaminants such as fuel and water vapor out of the crankcase and relieves any pressure that may build up in the oil pan.

Ordinary PCV valves have a fixed orifice, the M/E Wagner adjustable PCV valve is fully tunable with a vacuum gauge to fit the engine’s vacuum profile. The result is reduced moisture and acidic vapors in the engine’s crankcase, which means cleaner oil, cleaner engine internals, and reduced crankcase pressure that is often the cause of oil leaks.

010 heat riser passages in the heads
Typical of pre-’69 blocks: The hole to the left connects to the oil filler tube in the manifold (arrow A), the hole on the far right is for the road draft tube or PCV valve (arrow B). Also, note the heat riser passages in the heads (arrow C).
011 Gen II block accommodates roller lifters
The Gen-II block accommodates roller lifters, and the holes at the ends of the block and the heat riser passages have been eliminated.
012 327 intake manifold with an oil filler
This is an early 327 intake manifold with an oil filler. The small tube connects to the air cleaner as part of the PCV system.
013 serious port misalignment issue as the gaps show
While the Chevrolet Performance heads are drilled with the early intake manifold bolt pattern, there is a serious port misalignment issue as the gaps show.
014 dual plane aluminum intake manifold with an N O S Carter carburetor
We elected to use the new dual-plane aluminum intake manifold with an N.O.S. Carter carburetor, however it was not drilled for the new square-flange intake manifold.
015 vintage Offenhauser carburetor flange
Using our vintage Offenhauser carburetor flange, we drilled the necessary holes in the AFB’s baseplate.
016 intage AFB bolted to the new eight bolt intake
More new and old parts combined. The vintage AFB bolted to the new eight-bolt intake. ARP fasteners were again used.
017 GF 90 mounts to the intake manifold
An original-style A/C GF-90 mounts to the intake manifold with a stud that was added.
018 reproduction valve covers and mounting hardware from Classic Industries
Our original plan was to use reproduction valve covers and mounting hardware from Classic Industries, but due to the design of the new heads there was interference with the rocker arms.
019 aluminum PML center bolt Corvette valve covers
To solve our rocker clearance dilemma, we opted for a set of aluminum PML center-bolt Corvette valve covers.
020 PCV valve and fresh air intake
Inside the PML covers are baffles that allow the use of a PCV valve and fresh air intake.
021 adjustable PCV valve
This is an adjustable PCV valve from M/E Wagner—it allows airflow to be controlled during idle and cruise conditions.
022 PML covers drilled for a PCV system
We had the PML covers drilled for a PCV system. The M/E Wagner valve is on the right side and connects to the base of the carburetor.
023 fresh air intake for the PCV system
The fresh air intake for the PCV system comes from the air cleaner and connects to a baffled grommet in the left valve cover.
024 not able to use the original spark plug heat shields
We were not able to use the original spark plug heat shields due to the location of the threaded holes in the block.
025 wires from PerTronix with ceramic ends
To eliminate cooked spark plug boots, we chose wires from PerTronix with ceramic ends.
026 Note the Corvette spark plug wire shield and the support bracket
Note the Corvette spark plug wire shield and the support bracket (arrow) on the Powermaster starter.
027 brackets on the manifold bolts are for the spark plug covers
Similar to the right side, the left side spark plug wire cover and the wire guide are between cylinders 1 and 3. The brackets on the manifold bolts are for the spark plug covers.
028 MSD distributor with a mechanical tach drive
Another update is an MSD distributor with a mechanical tach drive. Note the ignition shield brackets are mounted by studs in the new manifold with spacers to place the distributor shield at the proper height.
029 ignition shield brackets also serve to locate the plug wires
The ignition shield brackets also serve to locate the plug wires. Unfortunately, the coil would not fit under the shield so it will be relocated behind the engine.
030 factory ignition shields are in place
Here all the factory ignition shields are in place. Zip Corvette supplied the factory-style wing nuts. Note manifold to carburetor heat tube for the choke.
031 HEI style distributor cap
We used an HEI-style distributor cap. For clearance under the cap, we trimmed off the wire retainers on the boots (compare these to photo 29).
032 Edelbrock aluminum pump from Summit Racing
Our crate engine came with a long, reverse rotation water pump, it was swapped for a short, standard rotation Edelbrock aluminum pump from Summit Racing.

 

Sources:

ARP (Automotive Racing Products)
(800) 826-3045
arp-bolts.com

Centerforce
(928) 771-8422
centerforce.com

Classic Industries
(800) 854-1280
classicindustries.com

Gandrud Chevrolet
(888) 284-7491
gmperformancemotor.com

M/E Wagner Performance
(579) 899-4544
mewagner.com

MSD
(866) 464-6553
holley.com

Pertronix
(909) 599-5955
pertronixbrands.com

PML
(310) 671-4345
yourcovers.com

Powermaster Performance
(630) 957-4019
powermastermotorsports.com

Summit Racing Equipment
(800) 230-3030
summitracing.com

Zip Corvette Parts
(800) 962-9632
zip-corvette.com

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