Whether you got them as stock or are planning on swapping them into your vehicle, the 317 heads are likely at the forefront of your mind when it comes to engine performance. The heads are such a small, seemingly simple component of the engine, yet they have the potential to have a profound effect on performance and fuel consumption.
What’s that, a tiny engine head can save you money and help you leave everyone in your dust? Then you are going to want to know which engine head to go for. And why, you might find, the 317s are one of the absolute best options out there.
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What Are Engine Heads?
Engine heads, or cylinder heads, are filtration devices on the top of the engine that controls the outflow and inflow of gasses into the combustion chamber as well as fuel deployment. Engine combustion is a complex process that involves more than simply burning fuel. Burning fuel so it ignites around the combustion chamber evenly and that burns evenly is so crucial to have an engine that runs efficiently.
Engine heads are supposed to ensure that the most efficient combination of fuel and oxygen is in the chamber at all times. The difference between good heads and bad heads is 20-70 brake horsepower and a 50% swing in fuel efficiency either way. It matters more than most people think.
What Are The 317 Head Specs?
317 cylinder heads are well known for being excellent for air flow in greater volumes than other such heads, like the 243 heads. The 317 heads have a chamber volume of 71.5ccs which is a full 15% more than its biggest competitor the 706 heads. And 20% more than the 243 heads. 317 heads are manufactured for a compression level of between 8.3:1 to 9.5:1.
It is possible to adjust their suitable compression range by machining the heads to increase airflow. The 317 heads have a chamber diameter of 3.923 inches and are rated for engine sizes up to 6 liters.
Are 317 Heads Good?
Many people consider the 317 heads to be excellent. not just good, and it is unsurprising that many vehicles come with the 317 heads as stock. The 317s are coveted in the aftermarket marketplace (mouthful) because they are the right size to fit onto most engines.
However, they are not always gauged to be the right compression level of most stock engines which are often about 10:1 as a benchmark. As we just discussed, the 317s are best suited for about a 9:1 compression ratio.
Which Heads Are Comparable To 317 Heads?
Many people like to compare the 243 and 706 heads to the 317s because they tend to be varying options for the same vehicles in the aftermarket scene. They are all relatively similar in flow volume and compression levels, but as mentioned, the 317 is objectively superior.
Some people find the 243 or the 799 heads to be a great alternative to the 317s, but, the 317 has a better flow through and is far superior in fuel intake efficiency. Out of all of the other heads on the market, the 799 is probably the closest competitor of the 317.
Are 317 Heads Good For Turbocharging?
317 are outstanding for turbocharging for one simple reason. Compression ratio! When most engines are turbocharged the compression levels in the combustion chamber must be substantially lowered, otherwise, you risk the engine exploding. Which is, shockingly, quite a bad thing to happen.
Normally, if you want to turbocharge something like a Honda Civic you would need to drop the engine compression levels from around 11-12:1 to 9:1 which is a HUGE decrease. While it is certainly possible, it does cause the engine to run a little less efficiently. With the 317 heads, you are already rated to be suitable for the right compression ratio for turbocharging, which means you can squeeze out the maximum efficiency of the heads.
What Are Machined Heads?
Engine heads are designed to allow maximum flow of both fuel and air in and out of the combustion chamber. However, cylinder heads that are mass manufactured are done so to be as quick and cheap to produce as possible.
This means their interior surfaces will be smooth-ish, but not polished. And, even if they were, over time they would start to struggle with a build-up of carbon and general wear and tear. When heads are machined, they are smoothed down with an electrical resurfaced. It is almost like a power sander but far more powerful, as it has to sand down metal!
Should I Machine My 317 Heads?
Machined heads are much smoother and allow for better flow in and out of the combustion chamber. While it is important to ensure you don’t machine them down too far so that they become weak and flimsy, it is almost always worth it.
If you are willing to spend the money. It is technically something that you could do yourself at home. But, it’s best to leave it to the pros. The margin for error is slim, assuming you even have the tools or know how to do it safely. 317s are well suited to be machined, just not by you (in most cases).
How Much Do 317 Heads Cost?
You can buy a full set of 317 heads for about $450 – $600 depending on how new you want them to be. If you want them to be ordered in new, machined down to the perfect level, and installed by a pro (swapping out all old) you can expect to pay about $1100.
As you can see, there is a decently wide range of prices one could expect to pay depending on what you actually want out of your cylinder heads.
The 317 heads are an excellent aftermarket upgrade. And, if you are thinking of buying a secondhand vehicle, enquiring about engine heads in pursuit of 317s over other heads isn’t a bad idea. Whether or not you have, or are currently in pursuit of, 317 engine heads you now have a great idea about why they are so popular.
And who knows, maybe the idea of buying a set of machined 317s and buying yourself an extra 50 horsepower is something you might now be interested in.