Intake valve's hissing like a MOFO!

Intake Valve’s not sealing

The motor was running well with the exception of some ignition issues that have been sorted out, so it got put away for the winter. Out of boredom today with the rockers backed off, and the intake off I put on the leakdown tester on the motor . 6 out of 8 cylinders have 90 to 100% leakdown and you can physically feel the air coming out of the intake runners. I never bothered putting the holes at TDC, Just a reminder, the rockers are backed off completely.

Im scratching my head, wondering how this could be, when it was running strong and didn’t show any sign of problems before. I cracked each intake valve stem with a rubber hammer to get the pop, in attempt to seat them more, but no luck.


Any input?

 

We have that problem even after the motor has sat for a couple of weeks. I believe that the methanol makes the seats rust up which doesn't help sealing. We have had 8% leakdown go to 45% . I would run the engine & then recheck. Don't forget that the leak gauge has a .080" hole so that that would be the max that can leak. I cant even get my gauge on a Moroso tester to go to 100% with the line totally disconected.

 

leak it down hot as to other post a little surface rust can build from setting open and it will clean it self up if it running good when it hot compression will seal the valve un less you have on that is way out of wack i had a similar deal years ago with a new motor leak it cold had the same problem called told me not to worry run it and i leaked it hot all was fine