Don't see much up here on Broncos but let's ignore that part it's still a Ford a 5.0 1991. I rebuilt the block 30 over the heads were both cracked so replaced them with a set from JY after building them and installing the motor turned over like an electric motor????? Come to find out after teardown it was a set of E6SE AA heads the original pushrods and lifters were replaced new so they were good, Pushrods seem to be to long have tried severaal sets still haven't hit the sweet zone. Am I mixing apples and oranges? Purchased a pushrod length checker first was to big and one lower was back order. Has anyone else had this problem??

 

3 questions do you have roller lifters?, or are you running a flat tappet cam?, and what length push rods are you using?
Ford went to roller lifters in trucks, 91 sometime, and all 92 and later are roller lifters.

bronco forum-->1978 - 1996 Big Bronco - Ford Truck Enthusiasts Forums

 

Sounds like you have push rods that are too long, and your valves are open because of it. You should count your blessings that the low lift of the stock cam and the dished pistons prevented you from doing serious damage.

 

To know if you have roller lifter, check the valley and see if you have the hold down "spider" bolted to the top of the block. If yes, you have (or should have) hydraulic lifters.

There is a bronco dedicated forum as linked above, but feel free to post here, also.