I have only 700 miles on my 383 sbc and was able to spin the hell out of my street tires with only have to 3/4 throttle. Now I have to go WOT to spin the tires and my hp is very low. I put it in the shop to Dyno tune and they tell me that my rear torque is only like rwtq318 and rwhp is like 302. I don't know what happened. One day I took the car out and ran fine, next day I have no more power off the lineor top end. Did compression test and all cylinders are within 180-190 psi, mechanical fuel pump pressure is 8psi. Changed spark plugs, wires, new race distributor, new cam, springs, lifters and still no difference.

Possibly cracked or damaged heads, or carb(even possible after dyno tune with changing squirters?)

Any clues would be very appreciated.

 

have you readjusted the valves since initial startup? might be a good place to start.RR

 

Check the ignition timing. Make sure it hasn't moved, and the dist bolt is tight.

 

Valves have been re-checked and dizzy bolt is nice and tight. Timing is set at 36 degress total advance at 3500 rpm.