Rebuilding an HP500
 

I have a 1999 stock HP500 with about 250 hours on it. I plan on rebuilding it this fall and would like more power.

1. How much more HP can I expect to get boring it 30 over making it a 509?

2. Since I will have the engine torn down are there any other suggestions for ideas to make more power and maintaining the reliability of an HP 500?

You won't feel any performance increase by boring the engine oversize but you should increase the compression to 9.5:1 with open chamber JE pistons. The most important point, when rebuilding the engine, is to get the top of the piston to within .040 inches of the cylinder head with a gasket installed. A tight quench.

If you don't want to replace the large rectangle port heads with smaller oval port heads for increased torque production and a 20 horsepower gain you should at least install a dual plane intake manifold. The Edelbrock RPM air gap will give you more power (10 to 15 HP) than the Dart single plane at 5200 rpm. Keep the stock carburetor.

The stock 500 HP camshaft is great, I wouldn't replace it with anything larger. Keep the stock ignition system.

Sincerely
Dennis Moore

Jack and Bobby, what horsepower will your changes generate?

Dennis and Budah
Are you suggesting the
JE Open Chamber Dome #123189 (Bore 4.469) 9.2@118cc

Thanks!:D

Dowhat,
I too have a 1999 HP500 with about 175 hours and I am thinking about having Express Marine in Deland rebuld it this fall/winter, change out the springs and "pepping" it up a little bit. I live down the coast on Merritt Island. Are you doing the work yourself or having someone do it?
Dean

I am living near St. Pete now, and I am not sure who I am going to have do it.

Thanks for everyones input.:D

Dowhat