All internal components will be new, as seen here.
Other than the block, everything in this engine will be new, so we will now continue with all the new parts we need to order. Everything we purchase for any engine we will ever build is going to be a balancing act between necessary quality, durability, and price. Better quality and better durability costs more, period. We have referred to this as a budget build, which in no way infers cheap. This engine finished with intake, carb, HEI Distributor, and Ignition wires would sell for about $5400. But since it is built to run on 87 octane, and is being limited to around 400 horsepower, the quality of components necessary to be reliable is far less than a small block sportsman circle track engine that may run $17,000 or more, or a 358 modified engine that could be up in the $30,000 to $35,000 range. So when we say budget, it’s all relative to the outcome we are looking to achieve.
We will be running an aftermarket cast steel crankshaft. Scat, Eagle, or Liberty Performance all offer similar quality cranks that will be in our price range. It will need to be a special “stroker” crankshaft, meaning we will be adding additional stroke to the engine to achieve additional cubic inches of displacement. A normal 350 ci crankshaft has a stroke of 3.484 inches, while our build will use a crank with a stroke of 3.75 inches. The stroke of the crank is the distance the crankshaft moves the piston from the bottom of its stroke in the cylinder (BDC), to the top of its stroke in the cylinder (TDC). The difference in this case with a 4.030” bore is about 28 additional cubic inches over using a 350 crankshaft. That’s about an eight percent increase in cubic inches for ¼ inch additional stroke.
The choices in quality of material and manufacturing technique of crankshafts are almost endless. Manufacturing technique refers to whether the crankshaft is cast or forged. Cast means the molten steel is poured (or cast) into a mold. Forged cranks are pressed into shape under extreme pressure and heat. The forging process produces a much more durable crankshaft. The casting process is sufficient for street applications up to about 400-450 horsepower. In racing applications, where superior tire traction is putting more load on the engine, that may limit the safe horsepower range to 350-375. Beyond these ranges it would then be advisable to upgrade to a forged crankshaft, at of course a higher price. Again since we are looking to achieve about 400 horsepower, and building this for a street application, the cast crank will be fine.
As for connecting rods, again Scat or Eagle have decent quality I-beam rods with 3/8” ARP cap screws that will be in our price range. There will also be a choice of using a press fit rod or a bushed rod, referring to how the piston will be mounted to the rod. Although this engine was originally designed to use the press fit rod (strictly a price issue), the pistons we have selected will allow the use of a bushed rod so we are going to spend a few more dollars and upgrade. Be careful when selecting a rod, in order to use a bushed rod, the pistons must have retaining clips of some kind for them to work. If the piston isn’t cut for retaining clips the piston pin must be pressed into the rod end.
From our computations in the dyno software we found we needed about a 17cc dish to work with the 64cc head we are going to use. We found a Keith Black hypereutectic piston available with an 18cc dish. This piston has a “D” shaped dish, which is of additional benefit, and will be explained in our next session under decking of the block. With the 18cc dish this will allow us to surface the heads until we get the required combustion chamber size for our final compression ratio of 9.7:1.
A quick note here about piston selection. The piston takes a tremendous amount of abuse in the engine. You need a piston as strong, but also as light as you can afford. The reason for strength is obvious, but the reason for being as light as possible may not be what you would expect. Everyone wants to run a light piston to lesson the rotating mass, making for a quicker reving engine. While that is one benefit of a light piston, the more important reason is to take stress off the rod. The rod and piston change direction twice for every revolution of the crankshaft. That means at 6000 RPM the piston is changing direction 200 times per second! The load on the rod at the bottom of the stroke is under compression, not nearly as abusive as trying to stop the piston from launching itself into the atmosphere at the top of the stroke and reeling it back in 100 times per second. This is probably the single biggest cause of rod (and therefore engine) failure. I hear some engineers at JE Pistons refer to this as "oil pan failure"…when the oil pan fails to keep all the parts of the engine together. Besides weight differences, different types of pistons will withstand detonation better than others. The hypereutectic piston is stronger than a stock cast piston, but not nearly as durable as a good forged piston, but again your budget will dictate what you can afford.
Next on the list is cylinder head selection. I’m sure I’ll get some argument on this, but I feel the single most important component for making power in an engine is the cylinder head. The two most important things affecting power are compression ratio and airflow. Compression ratio is a ratio of the cylinder head combustion chamber size in relation to swept volume of the cylinder. Airflow while influenced by intake, carb, headers, and camshaft, is predominantly a function of the cylinder head.
While cam selection plays a large part in the airflow combination, if you have decided on what type of cam you are going to run, they are generally all about the same price regardless of different specs. Cylinder heads though are not that simple. Generally speaking, on cylinder heads, whether at the original purchase, or in work done to improve them, more money spent is going to get you more horsepower.
That being said, we are going to see what we can accomplish with a relatively inexpensive (read budget) set of heads, by doing some additional work on them. As we said earlier we are going to use the Patriot Performance Freedom Series aluminum heads. At 64cc combustion chambers, and 190cc intake runners they should give us a good platform for our budget build. We will fit them with typical 2.02” intake valves, and 1.60” exhaust valves, and a single spring to match our camshaft requirements.
Which leads us into our next selection, the camshaft. We had already decided on using hydraulic flat tappet (that budget thing again). After doing various cam selections within the dyno software, we had it narrowed down to two selections. Although we had said we were going to go with the slightly larger cam to try to make sure we hit that magic 400 horsepower number, after talking with the engineer at Comp Cams, he suggested we use the lesser of the two final choices we had come up with. His reasoning was running this on 87 octane he was concerned cylinder pressures at low RPM might be to great, causing concern of detonation. Camshaft selection is a lot more than lift and duration. That’s why we still talk to the cam engineers quite often, and are not likely to be disappointed with their selection.
I will make a quick statement here about camshaft selection and break-in. When using a flat tappet camshaft (hydraulic or solid lifter) it is necessary to be aware of the proper break-in procedure and the oil to be used for satisfactory cam life. We will discuss this at greater length later during our dyno break-in session. But for now keep in mind that while the added expense of a roller camshaft can avoid some of these pitfalls, proper break-in and oil usage can avoid camshaft failures.
This covers the major component selection, we will discuss the smaller items selections as we begin assembly. Let’s get our hands dirty!