As cylinder head customers, you have a lot of choices in what you can purchase. There are a lot of different options to choose from, and when you research various companies and options online, you try to get a feel for who you can trust. While our company does have a strong online presence, we want all of our current and potential customers to have more than a good feeling about where their products come from. We want everyone to SEE where they come from! There is a lot that goes into our cylinder head production, not just in designing the castings but all the way to the finished product that you receive. We have been machining and building LS-based cylinder heads since 2004, and we have countless hours in research and development to bring our products to our customers. We ONLY specialize in LS-based cylinder heads! We do not divide our time between multiple platforms. All of our time and money is spent on building the best LS-based cylinder heads available! While you can read a lot on how well a company’s product performs, you do not always get the chance to see what type of operation is in place to produce YOUR cylinder heads. We are going to take you through a tour of our cylinder head production, the operation, what goes into our products, and why we do it so you can fully understand why Precision Race Components is the correct choice for your cylinder heads!
Our machining center houses all of our machines for our cylinder head and engine programs. This center is 5,000 sq. ft. of our 25,000 sq. ft. facility, and all of our CNC cylinder heads are machined on Haas 5-axis CNC machines. We have two HS1’s and one ES5. Each machine is dedicated to a specific line of cylinder heads: one for cathedral-port aftermarket castings, one for LS3 and LS7 aftermarket castings, and one for GM castings. We strive to have the vast majority of the most popular cylinder heads in stock! Anything that is not in stock can typically be built within two to three business days.
All of our cylinder heads are valve jobbed on our Newen single-point CNC seat and guide machines. We use two of these machines, one for intake and one for exhaust. This allows us to streamline the production of our cylinder heads, which helps not only with time but precision as well. We also use the Newen machines to ream the guides for all of our aftermarket castings. Many other machine shops will use a drill in a parts washer to ream the guides, which can prove to be very inaccurate. All of our machining process uses the best machines available to build the best product available. We hold tolerances to less than .0001”!
All of our valve jobs are custom-drawn for our cylinder heads specifically, and the Newen machines complete the valve job with precision. We use a 5-angle valve job on our cylinder heads, and valve jobs that could take an hour or more to cut on older, traditional machines can take as little as 90 seconds on our machines! We have $200,000 invested in our two seat and guide machines alone! This is a perfect example of how we go above and beyond to build the absolute best product on the market! Each machine will also check the run-out on the seat to confirm that the valve job was performed correctly and the machined surface of the seat is 100% round.
Every set of cylinder heads gets pressure-checked before leaving our facility. What this does is pull vacuum through the port to verify that the valves completely seal when closed. Every port of every set of cylinder heads is checked with the valve in place but without a spring kit installed. The pressure of the valve spring will force most valves to seal against the seat, but the key is to make sure it seals without the help of the valve springs. The precision accuracy of the valve job is vital to valves that seal properly, and it is also crucial to air flow. You can lose 20 CFM or more if the valve job is not done properly!
We use a Haas VF3 3-axis CNC machine for nothing but cylinder head milling. Every set of cylinder heads is milled to ensure a 100% straight and level deck surface. This provides you with a quality seal against the head gasket. Every set of heads is machined to match the customer’s setup! We mill each set of cylinder heads for a specific size camshaft. So, if you are running a 224/224 cam, you will receive more milling than if you were to run our MS4 (239/242) cam. We stock all of our cylinder heads with various mill numbers, so we will most likely have multiple sets of heads in stock that will match your setup! We know the exact piston-to-valve clearance with all of our camshafts, so this allows us to provide our customers with maximum compression given the constraints of their p-to-v clearance. We also do NOT charge for the additional milling! Whether we are performing a .003” clean-up mill or cutting the surface .030”, you will not pay any additional money. We want every set of cylinder heads to be perfect for your setup, so you will always achieve maximum power results. We will not leave any power on the table!
For the PRC dual valve spring kits, all seat bases and titanium retainers are machined on a Haas CNC lathe. We do not use outsourced or overseas parts, which allows us to set both our .650” and EHT .675” valve spring kit up with an install height of 1.810”. We do see a little variance in the installed height when using factory GM valves, but any of our cylinder heads with stainless steel valves will have very minimal variance, if any at all. The valve springs that we use for both our .650” and EHT .675” are NOT the same, old “gold” valve springs that you find with other vendors. The old “gold” valve spring is a weaker design with less closed and open pressures, and they have proven to lose their installed height with as little as 15,000 miles! The PRC valve springs are ONLY used by us, and they were specifically designed for us. Our valve springs were spintron tested against other major valve spring suppliers in the LSx market, and the PRC springs not only retained their closed and open pressures for more cycles than any other valve spring but they also did not lose ANY of their installed height! As with ALL components of the Precision Race Components product line, every piece in our valve spring kits are built in the USA!
Throughout each production run, we randomly pull cylinder heads to not only verify the quality control processes that were in place to that point but to also verify that the cylinder heads flow exactly what they are advertised to flow! It is VERY important to understand that there is a correct and incorrect way to flow cylinder heads. You must have the correct bore plate, you must use a consistent unit of measurement (we measure flow at 28.0” of water), and you MUST have a radiused inlet on the intake ports! We use a Superflow SF-600 flow bench for all of our air flow testing, and we use clay to create a radiused inlet. The radiused inlet is so important when testing intake ports because the sharp edge of the port will create a disturbance and show much lower flow numbers. You have to remember that when the engine is running, the intake manifold is against the intake port and the lip of the cylinder head is not a factor at that point.