Speedometer problem
 

I have rebuilt 1979 motor , Now the engine start and revs high at 3000 RMP, How can i slow the engine down please? If i turn the Distributor it slows but also the timing go out, The Speedometer indicates 100 miles /hour while standing still,Anyone knows cure for this please?

High idle usually means the idle screw on the front of the throttle is improperly adjusted and/or vacuum leaks in the intake. Leave the distributor for setting the timing.

Clean the grounds, check the wiring.

remove the throttle cable from the intake connection and see if this still happens if so then you have a throttle body problem if it goes away then have a misrouted throttle cable

I know having a hugemongous vacuum leak will cause this. Specifically the Decel Valve hoses. I accidentaly pulled the Decel Valve while the engine was running and I thought the engine was going to blow up. It will be on the opposite side of the Throttle Lever on Throtle Body.