Good-Win Racing Mazda Performance Parts

Cosworth Mazda MX5 Miata Big Valve Cylinder Head


MX5 2006-2015 · Engine

Part Number: 61-0304

Application: 2006-2015

Price: $3,229.00


Cosworth Mazda MX5 Miata Big Valve Cylinder Head
The Cosworth MX5 Miata CNC ported Big Valve cylinder head is the result of countless hours of development and testing. Starting with fresh large port castings, Cosworth precision machines both intake and exhaust ports to maximize flow. Cosworth then reshapes the MX5 combustion chamber to un-shroud the larger stainless steel valves. This MX5 head is then assembled using Cosworth hi-rev tapered springs along with new valve stem seals and retainers.

This Cosworth MX5 cylinder head is the key to making big power and will flow enough to support 300bhp. Picture supplied by Cosworth is not the exact part. Cosworth CNC ported MX5 cylinder heads feature dyno tested and flow bench proven ports, engineered for maximum usable power. Each new MX5 Miata cylinder head is ported on a 5 axis machine to ensure consistency and perfect port shape every time.

Additionally, larger intake (+1mm) and exhaust valves (+1mm) are utilized to help increase flow. Cosworth CNC MX5 ported Big Valve cylinder heads come complete with a performance valve job, hi rev (max 10,500rpm) valve springs with titanium retainers and are ready to install. Perfect for high performance MX5 Miata applications.

NOTE: These require an 8 week build time from date of order.

About Manufacturer: Cosworth Over the years we have developed in-depth knowledge of engines, engine components and engine management systems. This has been successfully used to supply engines to some of the most successful Formula One teams and vehicle manufacturers. Our unprecedented success in the performance market has fueled customer demand from diverse market sectors. In addition to the traditional markets, Cosworth is engaged in designing and developing, engines and components for marine, locomotive and aerospace applications.


Last week I spoke to Brian, I ordered a aluminum Koyo 37mm radiator for 97 Miata. Brian, you run a first class show! It arrived the next day. It is a fully polished work of art. The welding is perfect. The fit is perfect, old radiator slipped right out, new one slipped right in. Perfect. I am very pleased. Thank you.

-- Allan R.

Brian, just wanted tyou to know you've got another highly satisfied customer. I got my RoadstersportIII muffler on Friday, installed it in 20 minutes, looks and sounds awesome. I like the baffles out!! My new tires/wheels came Saturday, just got them on and test drove them. Fantastic!! And how they look--- just what I was after. I will add the front "mud flap" that looks like the rear one, for some stone protection, but the offset was just what I was working for. I'd love to send you some pictures for your photo gallery. If you'll send an adress via e-mail, I'll send some high-res photos showing clearances and side profiles, etc. The graphite spokes and polished rims really set well on my black car. Thanks again, me and my wallet will be back!!

-- Ken