Hooker 2.5" SBC manifolds

Part #'s 8525 = STANDARD PORT HEADS

Part #'s 8527 = D- PORT HEADS- PLEASE READ BELOW TO DETERMINE IF YOU HAVE D-PORT HEADS!

Downpipes from Flowmaster or Pypes WILL NOT bolt directly to these manifolds. The outlet flange is a 2-bolt design vs. the stock 3-bolt. Either weld the supplied flange to your existing downtube or have one custom bent.

Most Hooker manifolds have limited availibility until JANUARY 2023!! Please call before ordering.

Hooker's new cast iron small-block Chevy exhaust manifolds offer an increase in performance and visual appearance over stock-style manifolds. Their compact design fit into a wide variety of replacement and engine swap applications. This means you get the traditional look and easy fitment of a stock style exhaust manifold but now with a smoother, cleaner appearance, plus more modern features. These manifolds are cast out of high silicon-molybdenum ductile iron for high temperature strength and better resistance to oxidation and cracking. Internally these manifolds have a larger than stock 1 5/8-inch cross-sectional area and 2 1/2-inch outlets for better air flow and improved performance. Offered for both rectangular or raised D-port heads, these manifolds fit many popular GM applications including standard straight, Vortec straight and angled plug head designs. Finishes include natural, silver, black, and titanium ceramic. Gaskets and hardware are included, along with weld-on flanges to aid in downpipe installation.

Features:

• A smoother, cleaner appearance compared to original exhaust manifolds, while maintaining a factory style look and feel
• Made from high silicon-molybdenum ductile iron for high temperature strength plus resistance to oxidation and cracking
• Designed with a larger 1 5/8” cross-sectional area and 2 ½” outlets for better air flow and increased performance
• Available for either rectangular port or raised D-port heads
• Accommodates standard straight, Vortec straight and angled plug head designs for better application coverage
• Includes weld-on flanges for easier downpipe pipe installation (custom downpipe required)
• Available in natural cast iron or ceramic coated finishes (silver, black and titanium)
• Includes mounting hardware and gaskets for inlet and outlet flanges.
• DETERMINING IF YOU HAVE STANDARD OR D-PORT HEADS - It is important to understand the exhaust port shape on small block Chevy cylinder heads, specifically when it comes to header selection. With so many OEM and aftermarket cylinder heads available for these engines, the exhaust port shape can vary dramatically. In most cases this is not an issue. Round port, square port, something in-between, it really does not matter as long as the header flange seals properly to the cylinder head. Of course, those with race-only applications may want an exact match between the port and header. However, most of the time this is a non-issue, and will provide little to no benefit on the street application, hot rod, cruiser, or even many street/strip engines. One of the most confusing definitions we often hear relates to D-port cylinder heads. A customer begins by stating that they need a header that matches their D-port cylinder heads. Some time later, after receiving and installing their headers, they call and state that the headers will not seal against the cylinder heads---that they are leaking at every port. Why?
• The problem here, is that the customer does not have D-port cylinder heads---they have cylinder heads with d-shaped exhaust ports. Looking at the slightly exaggerated image below, it should be clear how this might be confusing. The D-Port roof extends well above the center line of the exhaust port, whereas the D-shaped port fits nicely inside what is deemed a standard port dimension.
  
• Added confusion occurs with some cylinder heads that have exceptionally large exhaust ports and also have a very pronounced D-shape, but does not quite fit the definition above. One example is the Pro-Filer 176 head shown below. Is this a D-Port or D-Shape? In this example, either a large port flange or a D-Port flange could work---as long as the header flange seals properly. The concern would be whether or not enough machined surface area exists above the port. The top of this port does not extend far above what would be described as a large square port. Additionally, Pro-Filer does not state anywhere in their documentation that this is a D-Port exhaust, what the port dimensions are, or what specific gasket to use with them.
  
  In contrast, the GM part #12556463 ZZ4 cylinder head is a true D-Port (shown below), as is the GM part #19300955 Fast Burn cylinder head (at bottom) Notice how high the port extends up.