When is old "old enough"
 

When is the actual time for an engine to absolutely need a rebuild. Is there a certain amount of miles that an engine can accumulate until the whole powertrain is the prime example of the old adage "you can't teach an old dog new tricks?" Can a stocck motor take some of the bolt-on's that most mustang owners throw at their cars? Is converting a 100,000+ mile car to a carb and porting the heads and adding some nitrous just too much for the factory blue oval, or will it take it? All opinions are greatly appreciated, Thanks!

black. do a compression test on all the cylinders. even better, do a cylinder leakdown test. either one will give you answers on what condition your motor is in. get us the results, go from there.

I don't think there is any set age that is "old enough". Why don't you run a compression test to see what condition your cylinders are in. If everything checks out ok theres no reason you can't put the bolt ons on. If the car was taken care of for the 100000 miles then there shouldn't be any problem.

BlackFireN20,

In addition to the compression test listed above, I would recommend checking crank shaft runout (especially on a manual transmission car). This is usually done with a dial indicator, but you can get an idea just by eyeballing. Also, you may consider monitoring oil consumption (1,000-3,000 mile incrimants).

Hope this helps.

What is crankshft runout?

Runout is a bad term for it, that is my fault. Crank shaft end play. The amount of distance that the engine's crankshaft can move from the front of the engine to the back. It tests the condition of the thrust bearing, and can give you an idea of the general condition of your main bearings.