Two months a go i got my engine completly rebuild and revised but now after i've been wearing it in i wanted to over 5000rpm the rpm's falls to zero and bangs really loud but engine is still running on stationary rpm's, to get him back to work i have to clutch and then he goes on!!!

Can somebody help me 've been looking crazy for a sollution??

The car is 100% standard 3dr 1986 cosworth


Sorry for my english i'm from belgium