Put a rebuilt 292 y-block in my Ford F100.  Turned fine by hand and started and ran OK, but rather high on idle.  So decided to change the carb.  Then had a hard time starting it and when it did start a loud clunking/clanking noise coming from top front of engine. Shut it off immediately hoping not to damage it ... sounded damaged.  Am not a mechanic and in small town not many familiar with Y-Blocks so need help determining what to go through to determine whats wrong.  Need sequence of checks to go through without using the starter or turning it over with the starter. Seem to be taking more steps backward than forward with this truck.  So any help is appreciated  

First thing I would do is pull the valve covers check the rockers and shafts, also who built the engine for you some people are not aware of the cam shaft spacer that does not come with the new cam . If it was not taken off the old one and put on the new cam that is your problem . Pull the valve covers then the timing chain cover. I am sure others will have more ideas 

Maybe something fell into the manifold when you changed carbs.? Hope not!

"FREE SAMPLE"

Pulling the valve covers is a good start.  I suspect you will find a bent or loose push rod.  Check the valve lash. Check to see if one or more of the rocker adjustment screws backed off.   Solid lifter engines are rare these days.  Your engine builder may have misadjusted the valves. If all looks good, you may need to pull the pan and look at the bottom end. Whatever you do, do not attempt to start your engine until you find the cause. 

The suggestion on removing the valve covers and giving a quick look for all the push rods being in place is a good one.  If all looks in place there, then I’ll suggest removing all the spark plugs first and simply look at them for potential damage.  If something fell into the engine during the carb change, the odds are good that the damage will be at one of the rear cylinders.  If undamaged, then a quick cranking compression test on all the cylinders.  If the compression is steady and high across all the cylinders, then removing the timing cover is next on the list.  I pull apart a good number of rebuilt Ford Y engines that have had the cam retention hardware put on incorrectly so that’s going to be high on the list for a ‘loud clanking noise from the front of the engine’.

Lorena, Texas (South of Waco)

The cam retention hardware in a Y-block engine can be tricky.  When I rebuilt my 292, I discovered my engine was made from parts of different engines. I had a heck of a time getting enough cam end play.  It seems there are more than one thicknesses of cam retention plates. Luckily, I had a complete virgin engine in my garage to salvage from. 

Cam components put on correctly as I checked that before installing engine and engine turned over by hand easily and ran OK then.  Was careful when changing carbs and covered intake during the process. Took valve covers off, did not see or feel anything out of place.  Pulled plugs and put socket on crank to turn over to TDC.  Turned well with no noise.  Just before getting to TDC the cranked locked up and could not turn it any more.  Bad note is this truck has Ford IFS front end and pulling the pan now requires pulling the engine.  Was not told that would be the case when front end was installed.  So probably pulling engine is needed to look it over.  This Ford the rear engine mount is the bell housing so all needs to come out ... Unless someone know how to check anything else without removing the engine.  Taking too many steps backwards on this project

Sorry to hear about your troubles.  Pulling the engine is standard operating procedure for any engine issue related to an early TBird.  I've had mine out numerous times. The hardest part is reinstalling the hood. Drilling a 1/8" hole in each hood hinge and using a drill bit for alignment makes it easier. 

Pull the heads first or use a bore scope to see inside.

find the two pistons that are up when it locks up and move them to the bottom and stick a small magnet down in the cylinder and hope you find a nut or something that might have been laying in the manifold and finally worked it's way into a cylinder. 

 lincoln/merc. y-blocks &mel's                                                               bucyrus, ohio.