Horsepower in a Box: What to Look for Inside a Crate Motor, Part I

Crate Lead“Horsepower in a box” is nothing new.  Yours truly sold a considerable number of Chevy LS7 454 motors in a speed shop over three and a half decades ago (at one time, we had 14 of them stacked to the ceiling, but I digress). There wasn’t much choice then:  Chevy sold the LS7 and a few different short blocks and that was it.  Chrysler didn’t have a crate motor and neither did Ford.  Equally important, those early Chevy crate motors were pretty much an assemblage of parts.  They were meant to be disassembled, inspected, clearanced and reassembled.  Honestly, some were decent inside. Others weren’t.

Fast forward to today.  All three Detroit automakers offer a huge number of crate motors. So do an equally large number of engine builders.  When you search the Internet for “crate motor”, you get more than 2.6 million hits!  Yikes.  Sure that doesn’t mean they’re all available motors, but you the get the picture.  The reality is, there are a number of decisions that must be made before you decide which crate engine to buy (or if you are a crate engine buyer in the first place).  What kind of decisions?  There might be more than you think.

Figure Out The Mission

One of the biggest decisions you have to make is to honestly evaluate the mission of the power plant.  For example, if you need to replace the tired big block in your motor home, you certainly aren’t going to slide a romping stomping, roller cammed, high compression ratio 572 under the dog house.  On the other hand, if you have a dual-purpose muscle machine that sees regular track duty, you’ll likely need (or want) more horsepower than an RV-style engine can supply.  You will find that when you go through the lists of available crate engines, some are more suited to certain applications than others.  First and foremost, decide what the engine is going to do.

The Parts In The Mix

Once you’ve determined the mission, then you can start to look at the parts used in the mix.  Different applications usually mandate different parts.  For example, a nitrous engine will likely have a piston ring that’s down further on the piston and may have a thicker dome.  An engine that’s destined for street strip duty will likely have steel rods.  Meanwhile, a power plant that sees plenty of high RPM drag strip use might require aluminum rods.  Because of those varying needs, let’s take a closer look at some of the options available inside crate engines.

Cylinder Blocks:  The majority of crate engines are based upon iron blocks.  Some use after market iron blocks.  Some crate engines use aluminum blocks.  Which is better?  It depends.  In some cases, to get the large displacement necessary for the engine combination, there is no choice but to use an aftermarket block.  Many factory blocks just can’t accept massive crank strokes and/or do not have the deck height necessary for very long stroke combinations (for example, some aftermarket big blocks can be ordered in deck heights roughly two-inches taller than a Chevy passenger car block).  And in other cases, Detroit manufacturers have revised block castings, leaving out features that are desirable for certain applications (case-in-point:  some late model Chevy crate motor blocks don’t have a provision for a mechanical fuel pump).  Some aftermarket blocks incorporate wider-than-stock bore centers, which allow for larger cylinder bores.  And some blocks use billet steel caps with splayed fasteners, which inherently, provide more ultimate bottom end strength (this feature is particularly useful in extreme output applications).

Reciprocating Assemblies:  Over the years, the sheer numbers of different reciprocating pieces has increased manifold.  Not that long ago, it was over the top to have a 4.25-inch stroke crank available for a big block.  Today, it’s commonplace.   4.75-inch strokers are just as easy to find as “little” 4.25-inch jobs.  Ditto with pistons and connecting rods.  They’re pretty simple devices.  And like crankshafts there are probably thousands of different combinations for the small block alone.  As pointed out previously, some combinations are built for nitrous.  Others are built to run on pump gas.  Others built for superchargers and so on.  Because of this, you have to really know what works for your combination.  Remember too that some rods are available in aluminum.  Others in steel.  Then you have the option of “H” beam rods or “I” beam rods.  Quality is another issue.  Some parts in today’s marketplace are made offshore.  Naturally, this drives the price downward, but it can also have an effect upon the overall quality of the engine.  And believe it or not, the quality of the offshore parts varies greatly too.  These are just some of the many issues you have to resolve when deciding upon the hardware that goes inside your engine.

Next time around, we’ll take a closer look at the top end of the engine (valve train and cylinder heads).  As you can well imagine, there are plenty of options for you to consider, and we’ve got some of them in the photos below.

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