This is our Chevy small block...
This is our Chevy small block that we use as a dyno mule ready for a new rotating assembly. What did it take to get it to this point? Glad you asked.
No matter what kind of rules are written to keep the costs of racing down, there are some facets of stock car racing that are going to be expensive no matter what you do. This is particularly true when it comes to the engine. Even if you’re racing a crate engine class, any engine is a complex piece of machinery with lots of moving parts which require an extremely precise fit and finish. That type of stuff just costs money.
If you race in a built motor class, the up-front costs are likely even higher. But the costs almost always evens out in the long run because the higher quality parts you will normally use in a built race motor will be a higher quality than you will find in most crates—this is true even if you’re building a Pure Street race engine—so they will last longer, perform better, and be much less likely to blow up at the worst possible time.
The key to saving a buck when it comes to your racing engine is to do at least some of the work yourself. After all, your time may be valuable, but at least nobody is charging you for it. So whatever you can take off of your engine builder’s plate and do for yourself is that much more that won’t be reflected on the bill.
Not all stress cracks are...
Not all stress cracks are visible, even after the engine has been thoroughly cleaned. Here, KT Engines’ Nate Allmond mag checks the block for cracks before we begin the machining process. Common areas for cracking are in the lifter valley and on the decks between either the cylinder bores or the cylinder bores and coolant holes.
A precautionary step that...
A precautionary step that should be taken on just about every rebuild is a quick line hone of the main journal housing bores to make sure they are still square. But before you can do that the caps must be “clipped” or cut down slightly. This makes the main bores smaller so that there is material for the honing bar to cut away and square everything back up.
If the main housing bores...
If the main housing bores aren’t parallel, it can create tight spots for the crankshaft. The worst case scenario is a spun main bearing, but more likely is simply unnecessary friction as the crank spins. It’s not death to an engine, but it’s wasted horsepower and if you’re going to the trouble to build a race engine you might as well ensure you’re getting all the power possible to the rear wheels.
Of course, there are some things that are best left to the engine builder with a dedicated machine shop and all the cool specialized tools that come with it. In this article, we’ll take an in-depth look at preparing the engine block for a race engine build. Some things require specialized machining equipment, which should be left to your trusted engine builder. We’ll take a look at exactly what these are, what they should cost and how they will help your engine perform at its best. We’ll also take a look at which steps are critical and which you can sometimes get by without, but honestly, if you’re attempting to race at your highest level, doing everything you can to make sure your engine block is absolutely perfect is always a good idea.
And then there are some operations that don’t require anything more than handtools. You may want to consider doing some of these yourself, either before or after you take the block to your engine builder. Almost all the steps we’ll discuss are valid whether you’re prepping a brand-new block straight out of the speed parts catalog, attempting to salvage an old soldier out of the junkyard, or simply going through a rebuild.
For this story we spent a lot of time at KT Engine Development which was kind enough to share with us the typical costs for most of the steps involved. Your local engine builder may have a different pricing schedule, and in fact, KT Engines owner Ken Troutman says he often charges less than the prices quoted depending on the shape of the block, but these should be considered an industry standard.
After a brief survey, here’s what we’ve determined are average prices for some of the most common tasks when it comes to prepping an engine block.
|Teardown and Inspection
|Bore and Hone
|Add Torque Plates
|Deck the Block
|Install Cam Bearing and Plugs
High compression race motors...
High compression race motors need all the help they can get to avoid head gasket failures. Heat cycles can cause the deck of the block to warp, so the block should be decked even on rebuilds to make sure the deck surface remains flat and square to the crankshaft centerline. Here, Kevin Troutman sets up the block in the machine before cutting a few thousandths of an inch off of it to square everything back up. Even when you have a brand-new block this step will likely be necessary because you’ll want to cut the decks down as much as possible in order to maximize compression.
Previously, the block had...
Previously, the block had the standard 4.00-inch bores and we planned to use the more common 4.030 piston size. Before boring the cylinder larger, KT Engines owner Ken Troutman measures the pistons to verify the size.
After verifying the piston...
After verifying the piston size, Troutman bores the cylinders to 4.025 inches. The remaining 0.005-inch is left to be removed during the honing process. It may seem silly to go to the trouble to bore the cylinders an extra 0.030-inch since it only adds approximately 5 cubic inches, but it’s the gain in compression ratio that we’re really after.
Before honing, Kevin Troutman...
Before honing, Kevin Troutman chamfers the edges at the top of the cylinder bores. This helps, making installing the pistons in the bores with the rings in place easier and also removes a sharp edge that can potentially be a cause for detonation. You can chamfer the bores later, but if you make a mistake now and scuff a cylinder wall it can usually be fixed during honing.
Ken Troutman hones the bores...
Ken Troutman hones the bores to the final size in three stages. Each stage uses a different type of honing stone so that we wind up with the best bore finish and proper crosshatch pattern for good oil control. We can’t tell you which stones should be used because the best options vary depending on many factors including the type of block material, piston and ring choice, and even the honing machine being used. Notice also that the block is getting honed with a torque plate bolted on top of the block. The torque plate mimics the stress a block will see when a set of heads is bolted in place. This helps ensure better bores when the engine is complete. It’s usually a few extra bucks to get the block honed with torque plates in place, but we consider it money well spent.
Now we’re getting into the...
Now we’re getting into the area where you can get the block back and start doing some work yourself. Here, the outer edge of the bosses for the oil galleries are rolled back with a grinder to create clearance in a more race-ready double-roll timing chain. If this isn’t done, the edge of the gallery bosses will rub the back of the chain. This is also a good time to chamfer all the other edges on the block (especially around the edges of the deck). Remember, if you do any of this work yourself, you’ll need to thoroughly clean and wash the block to ensure no steel shavings are left behind.
After thoroughly cleaning...
After thoroughly cleaning the block it’s time to reinstall the plugs. It’s always a good idea to spend a couple extra bucks to get a plug kit that uses brass freeze plugs. Race cars almost always use pure water in the coolant system, and brass plugs won’t corrode like steel ones will.
To help seal the edges of...
To help seal the edges of the freeze plugs—and make sure they stay in place despite the vibrations and stress of racing—apply a bead of red Loctite around the edges of the plug.
You can use a large socket,...
You can use a large socket, but one of the easiest ways to drive in freeze plugs is with a seal driver kit like you see here.
Make sure to use liquid thread...
Make sure to use liquid thread sealer on all the gallery plugs to reduce the chance of an annoying oil leak.
Installing the cam bearings...
Installing the cam bearings requires a special tool (we’re using one from Goodson), but if you plan to build your own engines, it’s a good investment. Chevrolet small-block cam bearings are stepped in size, so you have to make sure you get the right ones in the correct position. The correct placement is marked on the flap of the box, as you can see here. Notice that the fifth bearing housing bore is larger than the bores for number three and four.
We’ve added machinist’s dye...
We’ve added machinist’s dye to help it show up better in the photo, but you can see that the part numbers are also stamped on the outside of the bearing.
Finally, carefully drive the...
Finally, carefully drive the bearings into the housing bores in the block. Make sure the oil hole in the cam bearings is centered in the oil gallery groove so that the cam gets plenty of oil when the engine is at speed. Don’t try to install cam bearings without the proper tool. It ensures the bearing is pressed in place square to the housing bore and without crimping the shoulders of the bearing.
Here’s a shot showing the...
Here’s a shot showing the oil gallery groove in the block’s cam bearing housing bore.
Here’s a step that’s only...
Here’s a step that’s only necessary in special circumstances. While working on this story, Ken Troutman also repaired a block with a broken main cap for another customer. A stock block with two-bolt main caps can normally withstand up to 450 horsepower reliably, but if you’re building a 500-plus-horsepower motor or have to repair a broken cap, it may be a good idea to upgrade to four-bolt mains. This requires boring the mains to the proper size (which is shown here) and then honing. But remember, this is only necessary in special circumstances. CT