I have a 78 403 which I am installing in my 77 Cutlass S which on paper says about 185 HP from the factory. It has since been rebuilt with a mild cam, roller rockers, roller timing chain, edlebrock rpm manifold Holley 650 with vacuum secondaries, dual exhaust with headers and 3 inch exhaust.


Don't have the money to put it on the dyno so was wondering if anyone had a good guess on the increase in HP with the above additions?


thanks

 

if you used non shim gaskets and didn't bump compression you may make less hp. What compression is it roughly ?

 

403s did not use a shim gasket. I believe that the factory quit using them in 1973 but not certain about that.

In order to make a reasonable guess, we need piston and cam specs. Also, was any work done to the heads? And, you need a bigger carb, IMHO.