air leaking past ex. valve while changing valve spring!!!!!!!

[Pt109]

I am stumped bad. I have been changing the valve springs on my 2015 ls3 take out engine, using air to hold the valves closed and am experiencing air coming past exhaust valves. Initially heard the air and thought it was going past the rings. I have masking tape over the exhaust ports and noticed air pushing the tape out, not much, seems to be the same on each cylinder. Tha makes no sense to me what so ever. New cam is in but no rockers or pushrods in place yet. Supposed to only have 750 miles on it.????? Initially thought it may be a chunk of carbon or something. Looked inside the ex. port looks great, shot a tiny bit of carb cleaner in there and it just bubbles like crazy.
Does anyone have any idea??? Thanks in advance .

[1BADBET]

Put the locks and retainer on the valve without the spring and pull up hard while you fill the cylinder with air. If the leak stops it should run fine, probably just a non concentric valve job. Not ideal (not the kind of valve jobs I do) but if it seals with some pressure it should run ok.

[grease]

You probably want to lap the valves to make sure they seal.

[andrewb70]

I bet when the engine comes up to temp, it'll be fine. Don't sweat it.

Andrew