Fixing the Engine in a 50 year old Mustang

Engine after the rebuild
PicturesEdelbrock HeadsHolley Brawler CarbComp CamClutch

The above menu are links to pages with specific info and specs on each of those items

Return to the prior page My GT 350

I store my Shelby each winter. It sets for many months waiting for spring each year. When the warm weather finally arrives, it is always a great thrill to start it up and take it from the garage. The sleeper awakes once more. I think it is a complement to me that this car has started every year after winter storage since 1982. Well, in the spring of 2019, it started but immediately I could hear a knock in the engine. I quickly confirmed the noise was coming from the block. By the time I deduced and reacted the knock all but went away. I turned it off. Didn’t want to make it worse, whatever it was.

This section of this web page will be cover the planning and process to rebuild this engine. Something was wrong with the engine. Can’t drive the car with a bad engine. Step one was figuring out what was wrong then deciding if and how to fix it. And I was also aware if I am having the engine checked out and repaired it would be a good time to really have it looked at. I haven’t put that many miles on it since I got it but the last time that engine was apart was in 1983. It wouldn’t be a bad good idea to replace lots of things, like oil & fuel pumps, the water pump for sure. And this is a muscle car, so I might as well have it tuned.

The process I went through could be information here that would help you if you are thinking of rebuilding your engine. Or if you are curious about what I’ve done to this car with some explanations and details, here it is.

One thing I learned is it’s pretty tough to find a reliable engine builder. You need to ask around and to find someone you can trust with your engine and your car. Many of the shops I was referred to didn’t do carbs, fuel injection only.

The story about finding out what was wrong with my engine and what I ended up doing to fix it. Click below to go to that page. (These are the SAME links as on the prior page and on the menu above.)

Hauling my car to the shop, afraid to drive it


I decided I might as well enhance this engine while I was fixing it the bad head gaskets. I was pretty confident I could get some more horse power and torque out of it. The labor would cost the same, the difference would be the parts.

To put the target horsepower in perspective, what is the normal horsepower of a 289/302 engine? Horse power is stated at either the engine/flywheel or at the rear wheels. The ratings below are all at the engine. The usual assumption is the engine will lose about 20-30% horsepower by the time it reaches the actual rear wheels. The figures below are advertised gross horsepower at the engine.

  • The infamous 65-67 solid lifter Ford 289 HiPo engine was rated at 271 HP
  • The Shelby version of the HiPo 289 had a Cobra intake, a Holley carb and some headers and they called it 306 HP
  • 1968 Shelby 302 with a Cobra intake and Holley carb was rated at 250 HP. The factory version was rated at 230 HP.
  • 1968 Shelby GT 500 428 was rated at 335 HP (actual was closer to 400 HP)
  • The 1969 Boss 302 engine rated at 290 HP (Actual was closer to 373 HP)
  • The 1969 351 Windsor engine is rated at 300 HP
  • The small block 289-302 Ford racing engines were running about 350-400 HP
  • 2017 5.0 Coyote is 435 HP

I put my car on a dyno a few years ago at a car show. I had just taken it out of storage to attend my first car show of the year. The fuel was 5 months old and stale at best. It could have used new plugs and maybe an oil change if I’d known I was going to have it dyno’d. Plus the guys with the dyno told me I had a right rear drum dragging. The rear wheel horsepower was 192. Add 20% and the flywheel HP would be about 235.

My target was 350 HP. I wanted to add 100+ HP. That would make my car into a true high performance Shelby Mustang.

What did I end up with? The builder got 310 HP on the dyno after the build. A little short on the 350 but into the range of what the earlier Shelby’s had at 306 HP. Does it make a difference? The horsepower bumped up 30%. Amazing how that 3.89 rear end works with this extra horsepower. This is a different car. I haven’t really gotten on it yet. Been breaking in that clutch with 500 street miles. But it’s real obvious this car has more power. And it sounds like it has lots of horse power. Like my wife says, my car is loud and obnoxious.