3.7l 470 mercruiser engine pop

[Rkbigrich1]

84 GW with twin 470 IOs converted to electronic ignition and alternators. Port engine pops when starting, but once started and warm runs fine. Any ideas?

 

[Bt Doctur]

out the intake= stuck intake valve, too lean a mixture
out the exaust= burned/leaking exaust valve

 

[Rkbigrich1]

out the intake= stuck intake valve, too lean a mixture
out the exaust= burned/leaking exaust valve

It pops out the carb, a stuck valve would unstick? And like I said it goes completely away when warm not even hot

 

[Rkbigrich1]

It pops out the carb, a stuck valve would unstick? And like I said it goes completely away when warm not even hot

 

[fastjeff]

Could also be a lifter that's hanging up and holding an intake valve open.

Jeff

 

[o2batsea]

Of course the timing is spot on, yes?