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How To Spot The Difference Between Gen III/IV And Gen V Small-Blocks Just By Their Cylinder Heads

Gen III/IV vs. Gen V Chevy V8 Cylinder Heads

Brandan Gillogly Apr 8, 2015
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Now that Chevrolet Performance is offering LT1 crate engines, more and more restomods and Pro Touring cars are going to be seen with the latest direct-injection (DI) Chevrolet small-block. Here are six ways to spot the difference between Gen III/IV and Gen V V8s just by their cylinder heads.


1. All Gen V Chevy small-blocks are direct injected, so they’ll have injectors mounted on the intake side of the head, low in the valley, that are opposite the spark plugs. Because of their location and because they’re a bit noisy, direct-injection injectors are covered up in OEM applications. Port-injected Gen III/IV engines will have injectors mounted in the intake.

2. Unless the intake is completely covered, it should be obvious that the Gen V engines have a raised intake port for a more direct line of sight to the back of the intake valve. Note the distance between the top of the intake port and the valve-cover mating surface.

3. Valve order has been rearranged on the Gen V so that the forward-most valve on the driver side is exhaust. This is less obvious when the heads are installed, although the exhaust ports are offset slightly to indicate the switch.

4. There is no remaining raw cast aluminum on the end of a Gen III/IV head—it’s all machined—while the ends of Gen V heads show a casting mark.

5. Gen V exhaust manifolds use a five-bolt pattern, sort of like the Olympic rings with a row of three and a lower row of two. Gen III/IV use a six-bolt pattern with two bolts between the center two exhaust ports.

6. Center-bolt valve covers have been with the small-block for nearly half of its production life, but we’re partial to the original perimeter bolts that are back with the Gen V.


Double Injection

Some Gen V LT1 direct-injection engines with aftermarket forced induction rely on port-fuel injection to provide sufficient fuel when the power levels exceed the factory fuel-injection pump’s capabilities.

2014 6 2L LT1 2013 LS3 C Cylinder Head Comparison Rocker Side 2/2

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