Menu

Shop

Garage

Cart

Account

Products to Compare (max of 3)
X
Compare These Parts

How To Replicate LS Engine Dimensions with a Steel LS Mock Up Block

10/21/2022
Add Article To List

LS engines are being swapped into just about everything these days. We’ve seen them in Subarus, Porsches, Toyotas, and the list goes on. They offer cheap, reliable horsepower right out of the junkyard. Problem is, if you’re working to cram one of these engines into a chassis that wasn’t made for it, you’ll have lots of measuring and fitting to do. A mock up block will greatly simplify this process.

If you're looking to do something crazy, like this LS-swapped Subie, then you'll find a mock up block to be very helpful.
What is a Mock Up Block?

If you’ve ever worked with one of these mock up blocks before, you know what a game-changer they can be. Every part of the swap process is made easier by having a lightweight facsimile of your engine that can easily be lifted in and out of the chassis while you’re working. These work great for building mounts, checking header clearance, mocking up accessories on the front, or making sure the intake will fit under the hood. Not only that, but when you’re welding, grinding, or otherwise throwing sparks, your actual engine can stay safe and clean across the shop instead of sitting in the chassis and in harms way.

The steel LS Mock Up Block is a valuable tool to have in the shop. We recommend keeping a coat of oil on it to keep it from rusting when not in use.
Why Use a Steel Mock Up Block?

Most of these blocks on the market are made from cast plastic or foam with threaded inserts where critical accessories like headers and water pumps will go. In theory, these work just fine and will accurately simulate the engine as designed. But in practice, they tend to be a bit too fragile. We don’t need to tell you that intake manifolds, transmissions, headers, and the like are heavy. With too many of them hanging on that plastic block, they tend to crack and the threaded inserts have been known to pull out.

Here's where the Speedway Motors Steel Dummy Block comes in. These are made from 12 gauge steel, offering a great balance between light weight and the necessary strength to actually put them to work. We’ve already used them in the shop and had intakes, cast exhaust manifolds, accessories, and a transmission bolted on with no trouble. The bottom line is that these are tough enough to become a tool that you’ll use again and again.

What LS Engines Does this Mock Up Block Replicate?

In short, all of them. We know there’s a ton of variation across Gen III and IV LS engines. Cathedral port, rectangle port, iron block and aluminum, 4.8 to 6.2. But thankfully, their external dimensions are largely the same. The short block version of this dummy engine accurately replicates the block, allowing the use of your cylinder heads, while the long block adds simulated cylinder heads that adjust to replicate standard and LS7 heads.

Whether you’re upgrading from the old school small or big block in your muscle car or doing something completely outside the box, a mock up block is a handy tool to have in the shop. In fact, once you’ve used one, you’ll never want to attempt a swap without it again!

Products Featured in this Article

Related Articles

Gen III/IV LS Engine ID Guide
by Speedway Tech Team - Posted in Tech
10/4/2021
Looking to swap the venerable LS engine into your hot rod, muscle car, or classic truck? Take a look at our detailed identification guide for Gen III/IV LS engines before you hit the salvage yard or swap meet!
LS Swap Radiator Hose Adapter with Steam Port
by Joe McCollough - Posted in Tech
10/23/2020
This handy adapter is an inexpensive way to adapt an LS into your classic, muscle car, or truck. It takes care of the steam line as well as the hose diameter difference, allowing you to run a standard radiator with your LS swap.
LS Swap How-To Guide
by Joe McCollough - Posted in Tech
3/26/2021
LS swaps are nothing new, but they're still a little mysterious to some of us. Here is an overview of what you will need and what you need to know to swap some modern performance into your muscle car, truck, or hot rod!
Junkyard LS Swap Identification Guide: Part 1
by Speedway Tech Team - Posted in Tech
10/11/2018
Trying to decide which power plant to use in your latest project? Here's a quick guide of modern V8 engines for hot rodders to consider.
LS Engine Flexplate Fitment Guide
by Mark Houlahan - Posted in Videos
1/11/2023
The LS swap is no doubt still going strong, but if you’re planning to run an automatic behind your 4.8, 5.3, or 6.0L LS-powered ride, you’ll need to pay attention to a few items we discuss in this buyer’s guide.
How to Adapt LS Engine to 700R4 or Turbo 350 Transmissions
by Joe McCollough - Posted in Tech
1/6/2023
We show you how to keep that old GM transmission when swapping in an LS engine. Our LS swap adapter kits make it easy!
Install Guide: Upgrading a 5.3 LS With a Cam Swap
by Joe McCollough - Posted in Tech
10/31/2022
An LS cam swap can yield big power gains. And, you can do it at home. Here's how...
Easily Back Your LS Swap with The Manual Transmission of Your Choice
by Mark Houlahan - Posted in Tech
10/20/2022
Leave all the head scratching to us, as we have your manual transmission bellhousing solution for your LS swap all figured out already
Installing ICT Billet LS Motor Mount Adapters
by Speedway Tech Team - Posted in Tech
10/6/2021
Jordan shows us how to use ICT Billet motor mount adapters to bolt a 6.0 LS into his 3rd-Gen Firebird.
LS Radiator Guide
by Joe McCollough - Posted in Tech
8/27/2021
The radiator is an important part of that LS swap. Here are some options from the Speedway Motors catalog.
Error
X
Note
X
Ok