A good to place to start when choosing a set of headers is to think about how you are going to use your vehicle. Car shows and cruises? Closed Course competition? Daily Driver with emissions legality considerations? If you can pinpoint these things, it will help you to choose tube size, length, and finish.
Vehicle Year, Make, Model
If you are working on a standard production car, Year, Make and Model is the place to start, even though there will be several more considerations to think about.
Here are the key questions you’ll need to answer when it comes to your powerhouse.
Does the car have the original engine, or has it been swapped to something else? Engine swapping involves replacing the OE engine with another, often a late model engine is swapped into an early model vehicle to improve performance and reliability. Engine swaps open a new can of worms as placement of the swapped engine will heavily influence the fit of headers for the vehicle. The headers will be designed for a specific location in the engine compartment and that will depend on the mounts that were used. Our Tech experts can help you walk through this.
Are the exhaust ports and spark plugs identical to stock? Many aftermarket cylinder heads have relocated exhaust port heights or spark plug locations. In some cases, even factory cylinder heads will vary for a given engine family, and this can cause fitment issues with headers interfering with engine compartment components.
Are the spark plugs straight or angled? Small Block Chevys come in two distinct variations and not all headers will work with both styles, this is something you will need to know.
What is the shape of the exhaust port? We list the port shape in our catalog application guides, for instance Round, Rectangular, D-Shape, and “SAP” (same as port, for irregular shapes)
What are the exhaust port dimensions? Standard cylinder heads won’t be much of a concern here, but “ported” or aftermarket cylinder heads will have a larger port opening that you will want to consider.
Engine and Transmission Mounts
Check your engine health. Comprised mounts can cause shifts in the position that can lend to fitment issues that interfere with installation. Add to that the fact that many replacement mounts do not have exacting OEM specs and aftermarket mounts may be designed to change engine location slightly. In the case of Classic Chevrolets, even though a Big Block and Small block mount will interchange, they will NOT put the motor in the same position! To add even more confusion mounts can and will also vary by year and model. When these issues pop up, it’s not a problem with the header as to why it’s not fitting your car! And let’s be real, if you’re looking for new headers you should spring for proper engine and transmission mounts to seal the deal.
When it comes to a vehicle’s transmission, different configurations such as automatic versus manual or column shift versus floor shift can all have an impact on fitment. Remember, your headers weave through the engine compartment so considering your set up will help you choose headers that aren’t going to conflict with your transmission layout. In addition to the automatic/manual and column/floor shift, you should know what type of clutch linkage you’ve got, whether it’s mechanical or hydraulic and for trucks is it 2WD or 4WD?
Suspension and Steering
The suspension and steering configurations pose the same potential issues as your transmission, calling for another host of questions and considerations.
Does the vehicle have power steering? Power steering boxes are generally larger, and many classic cars have an external ram that can create header tube issues. Rack and Pinion steering conversions are popular these days, but don’t expect headers designed for a conventional steering box to fit. Look for headers that say they are specifically for R&P conversions.
Is the front clip original or has it been switched for an aftermarket front end? Like the Rack & Pinion conversions above, front clip and suspension conversions will take specialty headers as well.
Does your vehicle have A/C? This concerns classic cars where the A/C compressor mounts to the exhaust manifolds in many cases and in some cases, they require a special bracket or may not fit at all. Additionally, some A/C units on the firewall interfere with certain headers so they will not fit. We note this in the footnotes of our catalog application guides.
If the vehicle is driven on the street, Federal and State laws come into play. Most Pre 1975 vehicles (before catalytic converters) will not have much of an issue with legality as long as any smog equipment that attaches to the exhaust manifolds can be attached to the new headers. Vehicles with catalytic converters are another ball game. Federal Law prohibits any header installation that would modify or delete any emissions equipment. Each state has their own way of dealing with this and the most common, and strict, is the California EO program, where the manufacturer has proven to the state that the header does not delete emissions equipment and does not increase pollution, so the state issues an EO number that makes that header legal in all 50 states. Some states do not require this EO number, but the header still must retain all the emissions equipment and cannot increase emissions. ALL PerTronix Performance Brand headers are coded in our application guide as to the Emissions Legality so you can make an informed choice in your purchase. Any header that is not emissions legal is for Closed Course Competition only.
Wrapping It All Up
Taking the time to do the research up front will eliminate uncertainties and you will be equipped and educated to make the right purchase decision for your vehicle. You can always contact our dedicated tech team or download our catalog application guides for Doug's Headers, Patriot Exhaust and JBA Performance Exhaust which provide a plethora of fitment information to help you understand your individual vehicle attributes.