Re: Mustang Modifications - In the Beginning...
Ok time for a little update to this thread.
After much online research and reading of articles/books written by Ford Performance Engineers, I have a few additions/changes to make to the excellent info provided above.
Beginning Bolt On Modifications are suggested to be:
1. If you have an older speed density Mustang the very first mod should be changing it to the MAF system. Get that installed and tuned correctly so the engine is running good, then you are ready for the following modifications.
2. The first step should be getting more air into the engine with a low restriction MAF, larger TB and an increased flow upper and lower intake manifold.
2A. MAF - the MAF should be slightly larger than the throttle body you plan to use and if you plan to use larger injectors (24lb & Up) it will need to be properly tuned to work with the injector size you choose. Also when choosing the size, consider if you plan to install forced induction of any type. That may require you to install a larger MAF/injectors than would be needed for a naturally aspirated engine.
2B. TB - The throttle body as noted above should be slightly smaller than the MAF, but larger than your stock TB. A 70MM TB is usually the largest recommended for a "bolt on" modified street engine, however as with the MAF if forced induction is planned a larger TB may be recommended. For most "street" engines a 75MM TB will serve for a forced induction applications. Racing engines will usually require the 75MM as a minimum and much larger TBs may be needed for higher horsepower racing engine applications.
2C. Upper/Lower Intake - The stock 5.0 intake is pretty restrictive. Changing it out to a GT40, Cobra, Explorer or other suitable aftermarket intake is highly suggested. The stock intake is not worth the time or effort required to port it out and replacement is the best option. At this point you should decide exactly how far you want to go with your engine modifications. If you plan to replace the heads and camshaft, you should make sure the components match up and work well together. Manufacturers have HCI/Upper End (Heads, Cam, Intake) packages that are matched and designed to work well together. The Trick Flow HCI or "Upper End" kits are one of those that are available. They can enable you to make up to 360 HP with their kit added to your engine. The GT40 or Cobra/Explorer intake and the GT40X heads can enable you too make up to 300 HP when paired with a suitable camshaft.
3. Now, since you have more air coming into the engine, you need to think about increasing the exhaust flow. Adding a good set of headers and aftermarket exhaust should be next on your list. Bassani, Dynomax, Flowmaster & Pypes are a few of the manufacturers you have to choose from.
Recent online research and reading in the Ford Performance Engineering books have shown me that when installing new air intake components and exhaust components it is beneficial to have a "funnel" effect in both areas.
That's why I said above that the MAF should be slightly larger than the TB. Say if you use a 70MM TB you should use a 75MM or larger MAF. The "funnel" effect of those sizes will increase the velocity of your intake air flow into your intake giving you a slight "ram" effect which is better for HP production and performance than a lazy or restricted flow provided by a matched or reverse mismatched MAF & TB.
The exhaust can also benefit from the "funnel" effect, but in a reversed manner than the intake. Increasing the exhaust pipe size in steps from front to back will allow the hot exhaust gases to expand quicker and produce a better "scavenging" effect to help draw out the exhaust faster and draw in more intake air/fuel mixture during camshaft overlap periods. An example I saw recently they started out with 1 5/8" headers with 3" collectors (The very short section of 3" on the headers had a negligible effect.) which fed into a 2.5" X-pipe which fed into a set of 3" Flowmaster mufflers, then after the mufflers they stepped the size up to 3.5" for the tailpipes.
If I can find the article and dyno test on this exhaust again I will post it here.