if it was valves ?, then the compression would be to low to fire/ignite, and run ?, but if the timing is off ?, then this would force the ignited fuel out the intake valve, very posb the intake valve is not right ?, soo..maybe we are both on to something here .When timing is off for what ever reason it can be advanced or retarded, your getting fuel pumped into the exhaust and then it's getting ignited. The Valves may be to tight or just out off time. Check them and take them off the possibility list, It's free to look before buying more parts you don't need.
Even the worlds best agree with this principal,...... but in different words.When you do trouble shooting it's not what you assume is wrong it's the possibilities you eliminate. Checking to be sure is free!