Stock vs. Performance

Step One. Identifying your engine.

There are a few key pieces of information that we need before we can start building your system.

1. Camshaft – If the camshaft in your engine has been replaced at any point, you will need to provide the specs for it. Specifically, what we need is the intake and exhaust duration at 0.050″ and the intake and exhaust gross valve lift. Most camshaft manufacturers will provide these specs with a “cam card” that comes with it. If you know the part number of the cam, you may be able to find the specs by doing a search on Jegs, Summit Racing or Google.

a. Most camshafts are listed by their advertised duration. You will need to look at the “cam card” to find the actual duration, which is usually shown as:  Duration @ 0.050″. The advertised duration does not provide enough information for us.

b. There are usually one or two different ways that a camshaft will list the lift specs. What we need to know is your gross lift with rocker arm ratio factored in. If you have changed your rocker arm ratio from the factory spec, this needs to be factored into the lift specs when you place your order.

2. Compression – There are many ways to change your compression ratio, from changing the pistons to shaving the heads. If you are running a different compression ratio from the original spec, or even if you are unsure, please take the time to run a compression test so you have that information when you place your order.

3. Exhaust – When you place your order, be sure to have any information available about your exhaust system. Specifically, we need to know if you are running headers or the factory exhaust manifold, but any other information you can give us would be helpful.

4. Intake and Heads – If you are ordering a TBI system, we will need to know what type of intake manifold you have. We will need to know what type of carburetor bolts to the intake, and the bolt battern of the carburetor flange. In some cases, we require the customer to provide us with a blueprint of the carburetor flange, if we have not previously made an adapter plate for it. If you are ordering an MPFI or TPI system, we will need to know what type of heads you have on certain engines. If it’s a Chevy small block, we need to know if you are running stock style heads, or vortec style heads. If it’s a big block Chevy, we need to know if you have oval port or rectangle port heads.

5. Displacement – Make sure to give us any information related to changing the bore or stroke of the engine, and the exact displacement of your engine after these modifications were made.

Step Two: Once you have identified your engine, you are ready to order. If your engine is completely stock, without any modifications, you can proceed to the AFI Store and purchase your system. If your engine is not stock, gather up all the information listed above and contact us directly to order your system. In most cases, there will be a performance surcharge for any engine that has been modified for performance.