Skid Mark said:
My thoughts are:
- Header fit. The headers that are on now come forward and run back below the motor
- Leaded fuel
- Better performance and reliability from modern motor
Sounds like you could have a set of custom headers. Check the diameter of the primary exhaust tubes at the heads. If they are in the 1 7/8" range, they would cost you over a grand to replace. If they are this large, they are for High RPM operation. You will give up quite a bit of torque below 3500 RPM.
If you plan putting 20-30k miles on the engine, have the heads refitted with hardened valve seats to support unleaded fuel. Otherwise if it is a weekend warrior running race gas, don't worry about it.
Few small block Fords can compete with the revving capabilities of Boss. Performance wise, these were stout platforms for making 500+ HP at high RPMs.
Another plus for the Boss is the use of longer rods. They use the same length rod as the 289 (5.155 vs 5.090) and use a shorter piston height (1.529 vs 1.605) to compensate for the additional rod length. The rods also come with a larger rod bolts than the stock 289 or 302 rods. The theory behind the long rod is it allows the piston to stay at TDC and BDC for a fraction longer to improve breating and scavenging. It also increases the piston speed in mid stroke which gives the Boss an edge in higher RPMs vs a standard rod 302.
I'm using the same geometry in the motor I'm currently building (see sig). However, I don't have the stronger block nor the forged crank. 2 advantages I wish I had and could afford.
Keep the Boss. Keep it a solid lifter and build it to rev. The engine is a natural in an open-track or autocross car.
