What is a D-Port?

We often see confusion in what is considered a D-Port cylinder head for small block Chevrolet engine applications. The problem originates in the technical understanding of what constitutes a true D-PORT versus a D-shape. The D-Port roof extends well above the centerline of the exhaust port, whereas the D-shaped port fits nicely inside what is deemed a standard port dimension. The graphic below shows that the d-shape easily fits within the typical round or square port flange opening.

Where other header manufacturers use a typical flat header flange and gasket for sealing, the patented raised flange design of the Sanderson Headers requires different flanges for different small block Chevy exhaust port shapes. Other header flanges often block the top of the exhaust port on D-port heads. When using a Sanderson D-Port flange, the port is not blocked. However, using the wrong flange with a Sanderson header may expose open areas that will not seal, creating an exhaust leak.

Examples:

1. Using a D-port flange on a typical GM head (standard round, square, or D-shaped port), the header port flange open is larger (taller opening) than the sealing area around the exhaust port (additional details below, comparing two BRODIX Track 1® cylinder heads)
   
2. Using a standard Sanderson header flange on a D-port cylinder head creates a similar problem. The cylinder head exhaust port opening may extend above the raised flange sealing area, again creating the possibility of an exhaust leak.

Here is an example of a small block Chevrolet D-port cylinder head that requires the Sanderson D-Port header flange.

Vortec-Style Heads

NOTE: This issue concerns STRAIGHT PLUG Vortec-style small block Chevy cylinder heads, including the BluePrint heads

Vortec-style (including some non-GM aftermarket) cylinder heads use a different spark plug location than standard non-Vortec cylinder heads. Vortec-based heads move the spark plugs further from the chamber’s center and closer to the exhaust valve. This can cause a header clearance issue because it changes the spacing between the two center spark plugs, bringing them 1/2″ closer together. Some tubes require dimpling for spark plug clearance on exhaust headers with tight bends near the cylinder head (for example, the Sanderson CC158 header shown below). Dimpling of other tubes is sometimes required on other header designs affected by the spark plug location and up-down angle.

BluePrint cylinder heads are based on the Vortec spark plug locations. However, the BluePrint heads are manufactured with a raised exhaust port exit. This changes the up-down angle of the spark plug and the center-to-center distance of the two center spark plugs. Dimpling locations vary slightly between common Vortec-based and BluePrint header applications.

If unsure, please measure the center-to-center distance between the center pair of spark plugs on your heads. The standard distance is 4.5″ (11.43 cm) versus 4.0″ (10.16 cm) on the Vortec heads (See the image below). Additionally, one of the reasons we ask for the cylinder head brand, type, and part number is that every Vortec-style cylinder head does not utilize the exact spark plug location and angle. Having accurate information allows us to ensure that the proper dimpling is applied to the Sanderson header set for spark plug boot clearance during the manufacturing process.

Tube dimpling example, Sanderson CC158 for Vortec:

Additionally, the vertical spark plug location on some Vortec-based aftermarket cylinder heads may differ from the examples above. We may require the distance between the center of one of the mounting holes and the center of the spark plug hole (see image below). This ensures that dimpling is applied to the correct location(s) on the header.

Install Notes

1. The Patented Leak-Free Design that Sanderson Headers offers is the only leak-free flange design on the market. Do Not Attempt To Use Flange Gaskets! The raised flange on the Sanderson Headers may buckle the gasket during tightening and create a leak! Click here for the installation procedure.
2. Sanderson Headers are NOT emissions legal on pollution-controlled motor vehicles. It is the purchaser’s responsibility to verify local regulations for compliance.
3. Wrapping your Sanderson Headers with ANY thermal tape immediately voids your header warranty. The best thermal protection for your headers is the Aluminized Ceramic Coating, available for every Sanderson Header. Please read our tech article on thermal coatings and header wraps.

Sanderson Warranty

Limited 5-Year General Warranty

Sanderson Street Rod Headers strives to supply our customers with the highest quality parts and services in the street rod industry. In keeping with this, we warrant and will repair or replace, at our option, after an inspection in our facility, any of our products that we found to have failed due to defects in either material or workmanship.  This warranty is activated by the return of the Warranty Card enclosed with every pair of headers. It is effective for FIVE YEARS * from the date of purchase, as indicated on the original invoice.

This Warranty does not cover products that fail due to improper motor tuning, alteration, disassembly, or damage caused by racing, misuse, neglect, abuse, improper installation, and/or accident or when used on applications that were not designed or approved. We are specifically not responsible for the costs of removal, installation, transportation, destruction of other components, inconvenience, loss of time, or other personal damages or for any other associated costs, including the application of aftermarket coatings applied by others. Sanderson Street Rod Headers shall not be liable for any and all consequential damages occasioned by the breach of any written or implied warranty pertaining to this sale in excess of the purchase price of the product(s) as found on the original invoice.

WRAPPING HEADERS WITH THERMAL TAPE VOIDS THE WARRANTY.

* Extremely compact header designs that locate the collector close to the exhaust ports are very sensitive to engine tuning. Improper air/fuel mix or timing of ignition and/or valvetrain can cause early failure due to excessive heat. For this reason,  part numbers CC2 and CC3 are offered with a two-year warranty period only. This includes header sets that utilize one of these headers as part of the set (part numbers CC4 and CC14, for example). The compact header side will hold a 2-year warranty. All other Warranty conditions apply.

Downloadable Version