putting TO-30

Recently I had posted about a problem with my 52, TO-30 when I started the engine all I could get was idle and it was pushing air pressure back through the air intake it would sit there and idle and make a putting sound all of you said it sounded like a stuck intake valve so I removed the head and found one of the intakes carboned up removed all the valves, and had a local shop do a valve job purchased a valve gasket set and reinstalled everything went well, started back up and same problem as before still pushes air back through the intake and will hardly idle
I have run the whole engine process through my head and I am missing something where could the pressure be coming from ????? HELP
Clearfield.

Well
The problem is solved I want to thank u all You all gave me alot of good ideas but none of them seemed to lead me to the problem I had posted this on the 9N-2N-8N site someone there said to take a look at the exhaust maybe plugged so today I onhooked the pipe from the manifold and BINGO it started up
I then hooked the little buggerback up and same problem back again so I removed the exhaust pipe and turned it on end and there must off been3-4 cups of oats and corn come out of the pipe I then tried to force air press into the inlet and it is plugged solid no wonder the little fergy
could not run thats the reason it did try to idle
there was so much press that it was pushing back through the intake valve evertime one of them opened and then it was pushing back out the air intake Just wanted all u fine folks to know incase some day u go to start the little tractor up and air starts pushing back out the air inlet check the exhaust before u go tearing the engine down .
clearfield

Seems a little mouse had found a good dry spot to store up his food for the winter.