Entry-Level Racing - Economical Race Engines
Making The Right Decisions To Build Horsepower On A Budget
From the November, 2004 issue of Circle Track
By Jeff Huneycutt
Photography by Jeff Huneycutt
Building a custom race engine...
Building a custom race engine is difficult and best left to the professionals such as our contacts at KT Engine Development. However, assembling an engine to stock specifications is a lot easier with the help of rebuild kits from providers such as Day Motorsports-and it can save you money.
There are two ways to race cheap when it comes to Pure Stock level racing engines: Race junk that's cheap up front but won't last, or use a well-prepared block that uses economic or mostly stock parts that will last a season or more. The second option is more expensive up front but should be more powerful and actually save money in the long run compared to the barely-running junkyard motor that blows up after just three races.
Engine rules for the entry-level racing classes-everything from Enduro, Pure Stock, Strictly Stock, and others-are normally based on keeping everything in the engine as is from the factory. No aftermarket cams, lightweight valves, or high-zoot springs. Considering that you can buy OEM replacement parts for pennies on the dollar compared to racing specific hardware, limiting engine parts to "stock replacement only" in entry-level race cars makes good financial sense. There will always be racers in a hurry to get on the track that will buy any junker that runs and pray for the best, but a well-prepared engine will run better and last longer any day of the week-even with the same stock replacement parts.
The key to winning in the stock classes is attention to detail. Even if it still runs, an engine with 100,000 hard miles of road work on it is bound to be worn and not as efficient as it used to be. Fortunately, engine rebuild kits are both plentiful and affordable, especially for the venerable Chevrolet 350. You don't have to have the pedigree of one of Rick Hendrick's engine builders to put one together yourself. You don't have to understand every facet of engine theory or have written a master's thesis on valve timing to properly assemble an engine. If you are meticulous and comfortable around tools, you can do it. If you don't have experience rebuilding engines, find a friend who does and ask him or her to coach you, or check out the many books available on engine building.
The block we're using for...
The block we're using for our project is the ever-popular Chevy 350. Because this engine is so popular for racing, rebuild kits are plentiful, and it shouldn't be too hard to find a racer friend familiar with assembling one. Here, the cylinder bores in our block are being honed so that the cylinder will be good and round. The cylinder walls are also given a crosshatch texture in this process that improves cylinder oiling.
You can take the money you save and spend some of it on quality machine work on your block and heads. The key to an efficient and durable engine is close attention to tolerances. A quality machine shop specializing in engines can perform critical checks and tell you what, if any, part of your block needs work. For example, if the main bores are out of alignment-usually from detonation-your engine will still run, but the mains will be too tight against the crank journals in some locations, which will cost you horsepower and put the engine at risk of spinning a bearing. In the greater scheme of things, a little money spent on machine work up front is a lot less expensive than buying two engines in one season because the first one grenaded on you.
This story should help you get an idea of what is involved in assembling your own engine as well as the type of services a quality machine shop can provide (in our case, KT Engine Development). Giving you the blow-by-blow for every step of building an engine is beyond the scope of this article, but we hope it gives you some ideas for getting a legal and financial advantage on the rest of the field when the rules call for "stock replacement only."
What's It Cost?It's easy to tell you that good machine work on your block and heads will save you money in the long run without telling you what it's going to cost up front. To give you a better idea of what certain machining processes cost, we've compiled a list of average charges at most engine shops. The numbers are estimates that you will generally see, but if you find a machine shop that charges lots more than this, you can ask why. Also, it's just as important to be skeptical of any shop that charges significantly less because they might be cutting corners and sacrificing your quality for their time. Hopefully, the block you use for your foundation won't require every one of these processes, but it's also rare to find an engine with 100,000 miles on it that doesn't need any machine work.
|Process ||Cost |
|Align-hone mains ||$150 |
|Balance crank ||$200 |
|CC head ||$75 |
|Bore cylinders (8) ||$150 |
|Install cam bearings ||$20 |
|Deck block ||$125 |
|Deck heads (2) ||$50 |
|Pressure test cylinder heads (2) ||$100 |
|Hone cylinders ||$100 |
|V-8 valve job ||$150 |
If your donor engine hasn't...
If your donor engine hasn't been damaged from overheating or detonation, it's likely that both the crank and connecting rods are reusable along with the block and heads. Still, it's a good idea to clip the caps and resize them (shown here). This process ensures that the rods are nice and round. Otherwise, it will squeeze the rod bearing against the crank journal. This can cause the bearing to shed layers, putting metal into the system, and eventually spin a bearing.
OEM rods aren't normally balanced...
OEM rods aren't normally balanced as well as you would like for a racing engine. Plus, clipping and resizing the rods can throw them further out of balance. It's an easy and relatively cheap fix to weigh and balance your rods.
Stock rods usually have a...
Stock rods usually have a pad of metal on both ends, which is there expressly to make balancing easier. Here, Kevin Troutman of KT Engines grinds some of the metal off one of the pads to bring a rod into balance. If the rods, pistons, and crank are all in balance, it reduces vibrations and makes the engine more efficient at turning the chemical energy from the fuel into kinetic mechanical energy.
If you want to reuse your...
If you want to reuse your crank, it's always a good idea to have it magnafluxed to check for cracks. Even if nothing is done to the crank, the piece must be thoroughly cleaned before reassembly. This includes the oiling holes, which can be done with a small, circular brush. Cleaning doesn't have to be done in a solvent tank such as this. You can do it in your driveway with a water hose and a bucket of soapy water. Just make sure to apply a coat of rust inhibitor such as WD40 after you are done.
Day Motorsports provided us...
Day Motorsports provided us with a rebuild kit, including a timing set and all the gaskets and bearings we needed.
It is tempting to reuse your...
It is tempting to reuse your stock pistons, but it's not always the best idea. For our engine, we decided to upgrade a bit. Even though we won't be upgrading the original horsepower significantly, OEM cast pistons are a liability because they simply are not designed for 30 laps around a half-mile track at wide-open throttle. Probe Industries had the Street Stock racer in mind with these pistons. They are high-quality forged pieces that can easily pass for stock. They are targeted for claimer engines-affordable so you can stand to lose them, but good enough so that you can win with them.
Our main bearings are installed...
Our main bearings are installed in the block. Troutman says if he could perform only one machining operation on a race block, it would be to align-bore the main journals. If a cylinder isn't bored and left out of round, it will only make the engine run poorly, he explains, but if the mains are out of alignment, it's an invitation for a blown engine.
Stock rods use a press fit...
Stock rods use a press fit to hold wristpins in position. This requires heating the small end of the rod to get it to expand enough to fit over the wristpin. There are electric fixtures for doing this, but most engine builders simply use a torch. This may appear to be simple and something you can do at home, but we don't recommend it. Beyond the safety and fire issues, the wristpin (with the piston installed) must be centered over the rod before the assembly cools and everything hangs up. Needless to say, it's a lot easier said than done.
Once the rod is properly sized,...
Once the rod is properly sized, you can take it away. To make sure the rod bolts are properly seated, most bolt manufacturers recommend that you torque the rod caps to the rods three times before assembly.
To get the proper torque specs,...
To get the proper torque specs, the rod bolts must be lubricated. Some manufacturers, such as ARP, provide their own moly-based lubricant. Others specify a certain type of oil. Because it can affect the torque value that you get, make sure you use what the manufacturer recommends.
Troutman puts the rod bearings...
Troutman puts the rod bearings into place. After this step, make sure you check the clearance between the rod bearing and the journal with the rods properly torqued. You can do this either with a dial bore gauge or Plastigauge. The dial bore gauge is vastly more precise than Plastigauge, so if you plan to assemble more than one engine in your lifetime, it's probably worth the investment.
After putting assembly lubricant...
After putting assembly lubricant on both the cam bearings and the cam lobes, slide the camshaft into place. Be careful not to bang the cam around in the engine, as either a chip on the lobe or a scratched cam bearing can spell trouble.
Once you have both the cam...
Once you have both the cam and crank in place, you can install the timing set. A stretched timing chain is murder on valvetrain timing, and a new chain is good power. Normally, you will want to start with the cam installed "straight up," which means zero degrees advanced. Our timing set from Day Motorsports provides options for either advancing or retarding the cam for further adjustability later on.
Another note when assembling...
Another note when assembling rings on your pistons: Install your separator ring (the gold corrugated one) before your bottom oil ring. It may seem easier to install the bottom oil ring, then the separator ring, and, finally, the top oil ring, but it doesn't work that way. The separator ring has a small kickout around the inner portion designed to hold the oil ring out and against the cylinder wall. It has to go in first so that both the top and bottom oil ring can rest against it.
It can be tempting to steal...
It can be tempting to steal a page from the high-end racing notebook and try a set of low-tension rings. But if you are using stock replacement pistons, it's probably not possible. The ring lands in these pistons are too large. Using rings that are a poor match for the pistons is a common mistake of rookie engine builders that costs power.
It's the worst feeling in...
It's the worst feeling in the world to spend untold hours cleaning and preparing all your parts only to scratch a crank journal on assembly. Unfortu- nately, that's too easy to do. Avoid this frustration by using a pair of rod bolt sleeves to protect the crank when you are installing the pistons.
A high-quality head gasket...
A high-quality head gasket is a must for racing. Also, you can gain a slight edge by making sure you use the thinnest gasket possible. Gasket thickness can make a difference in compression, and we all know more compression equals power.
Be careful when installing...
Be careful when installing your pistons. These Probe pistons are marked with an arrow that should be pointing to the front of the engine. That's because these pistons have an offset pin, and if the offset is turned backwards, it will cause the piston skirts to rub the cylinder walls.
As we mentioned before, compression...
As we mentioned before, compression is your friend. If you are running races that are no more than about 30 laps on a half-mile track, a stock engine will probably hold up to as much as 10.8:1 compression. On a Chevrolet 350-cid V-8, that magic number can be reached with 70cc combustion chambers, flat-top pistons, a thin head gasket, and a zero deck block (the piston tops are even with the deck of the block at TDC). If your rules don't say anything about decking the block or heads, this is easy to do. Of course, compression numbers over 10.5:1 will probably require at least 93 octane fuel. Race fuel is the best bet if it's allowed. Ours show the pistons are below the deck 0.005 inch at TDC.
Don't even think about using...
Don't even think about using the original springs. Replacement springs are cheap and ensure that your valvetrain can reach its full potential.
If your rules are a little...
If your rules are a little more lenient about what's on the exterior of the engine, look for a quality circle track racing oil pan. A stock pan is sure death to an engine racing on an oval track. A racing pan is built with baffles and kickouts to make sure that oil stays near the pickup even under hard acceleration and left turns.