Need Advice to build the engine on a 66 289

1). Is it an automatic, or a 3 speed ? If so, then putting in a 4 speed,toploader,transmission will transform the car into much more fun. Automatics are boring, 3 speeds don't have enough gears (and 5 speeds are too fragile)" imo the 4 speed toploader is bulletproof, and can take some dragstrip action without complaint..

2). Change the intake to a Cobra Hi Rise, or air gap intake, and the exhaust to a 2.5" Magnaflow stainless system

3). Change the rear end gearing to a 3.25 or 3.50 ratio traction loc

Z

Hi,
well it mainly depends on 2 things:
- How are you using your 66 Mustang (Daily, Race, ...)
- How much will you invest in you rebuild (time, money)

I myself, I rebuild my 68 302 engine last year. Bored over, new pistions, all new bearings, and a nice little edelbrock performer cam.
I also redid the whole oiling system (pump, shaft, pan) all for more volume.

some time later I added a weiand 4v intake and an 4100 AUtolite.

Next upgrade will be edelbrock aluminum heads.

You have alot options: roller cam, roller rockers, aluminum heads, intakes, electrical ignitions, carbs...

The most improvement you can get on an engine is to let it breathe. Heads, Cam, intake, carb, and exhaust. But all depends on use and budget. I run a 331 stroker at 420hp in my 67 and it's an absolute giggle machine. But it doesn't take that much to make them sporty.


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I agree with what has already been said, but would add that a 4-bbl carb and intake, headers and exhaust are relatively easy, cam and heads a little harder. I've done the first but not the last two on my '66 289. Those are probably a little beyond my expertise at this point. But if you are going to do all of them, do them all at the same time. I'd also change the timing chain and water pump while everything is apart, just to hopefully keep from having to tear it all down again at some point in the future.

Compression gauge and leak-down tester can be very helpful here, and cheap to buy. Using these tools can let you know how well your engine is up to task of what you are asking out of it. Using these diagnostic tools are very helpful in determining the condition of the motor and will let you know of any problems you may have and where to "start spending the money". A fresh engine will always react better with high output bolt-on's, worn motor not so good. The biggest improvement I made to my bone stock motor was to upgrade the ignition system, got rid of the points and condenser system. Started way better, idle much nicer, and higher rpm's and don't have to rat hole a set of points in the glove box.....The rule of thumb here is if you want torque spend money on the bottom of the motor, want HP spend the money on the top. If you want both, well you know where to spend the money.