Ok so I am new at this and will attempt to give all the details. I have an 87 f250 7.5l 460 4x4 carburated engine. Guy I bought it from said he took out the smog and egr. When I bought it it ran mediocre at best. Burned a lot of oil and got around 6mpg. Engine light would flash after it got warm, vehicle would not like to go over 55 most of the time and eventually die and not start again until it cooled off. Had an old leak down by oil filter from the timing cover. Rear fuel tank has been disconnected and main 19gal tank has a different line the guy I bought if from ran, in line electric fuel pump from what I can see, fuel tank sending unit/gauge doesn't work.
Stuff the guy before me said he replaced/rebuilt. Rear brakes, axle seals, new fuel line, valves, rockets, push rods, springs, intake gasket due to leak, valve cover gaskets, oil- that is what I remember off the top of my head.

Ok I think that gives the back story first the most part. Fast forward 6 months and we are at today. I took the front I'd the engine off with my father in law who is familiar with older vehicles and is a genius if you ask me but he lives 3 hrs way and I want to try and get this running better sooner rather than later. Replaced the timing chain since the cover was off, set the time according to the book, replaced harmonic balancer, new gaskets all around, water pump seemed in good working order. This was all done because of the oil leak and I was in there and there was a lot of slack in the old chain. Put it all back together, no more leak and it started but I needed to find TDC to set timing again, got that figured out and was pretty decent. Started and ran again mediocre or a little better. Still the same issues listed above minus the leak. Replaced plugs, wires, checked distributor cap and rotor and the guy before did indeed replaced them. Ignition coil was also replaced. Around this time is when I realized the guy before me messed with some of the electrical and there was no EEC adapter to hook up a OBD1 reader---i have been told my truck never had one and also I did but it has been removed---if you have info on this please share!

ok so all the stuff mentioned above replaced, I also did a compression test, numbers were all +/- 5-10 and fairly decent 120s-130s. No more than 15lb difference if I recall accurately. Still burning oil and fuel and sounded rough. Checked valve spacing, noticed the 4th cylinder (last cylinder on left side from what my repair manual tells me) last valve on that cylinder was super loose. Tightened it but noticed there was give in the lifter. Boom, thought I solved the issue. Pulled my intake gasket after setting the valves minus that one and pulled the rid, retrieved the hydraulic lifter- it was .25 in shorter than all the others and had a pin hole in the bottom-this is why it would hold pressure but why was it so much shorter. Cam shaft was my guess. The lobe looked healthy as did the rest of the cam I could see. Put everything back in order. Torqued everything back down. Rechecked valve spacing, installed valve covers. Ran great for 1 week, no detonation, backfiring, would go around 60-65 for about and hour then I could shut off for 20 min and do it again. This led me to believe it could be the charging system and the engine was good to go. I was wrong, engine started missing again, I rechecked timing with TDC, checked firing order, changed oil to heavier 5w30 as recommended. Checked my valves.

so I have a check engine light on constantly, when the truck runs I hear a matallic click from the left half of the engine, while idling when I press on gas there is no misfiring/backfiring. When I put in drive and drive around my block the truck has no power, misfires/pre detonates. It does after it warns up, read on here it could be because of the 2g alternator and to do an upgrade so I bought a 130 amp reman alternator and will hook up after I get the engine issue fixed. My father in law is determined to figure it out and keep putting money into the engine- I am in need of your expertise please!

 

I don't believe you have an Engine Check Light. Maybe an Emissions Light? What is in the lens when it lights up? "Emissions""Emiss"?

 

So, I believe you have the DuraSpark Ignition system, and no EEC, so you would not have an OBD1 connector.
Post a photo of your distibutor & connectors, also photo the box on the drivers side fender skirt, and it's 2 connectors.
May look like this;


These boxes sometimes fail when they get warm, and when they cool off they are ok again.

 

This is most likely your ignition system, this is from an 1986 book, I'm on the road, so I cant compare to my 1987 book.

 

"It does after it warns up" Can you define what you mean by this ?

 

I've seen these symptoms when the distributor has issues. (play in the distributor shaft, also the electronic pickup in the distributor fails with age)
Any idea of the age or history of the distributor?

 

Dying when warm and then re-starting after cool-off, is a classic sign of a failing Duraspark 2 module. That is until they fail altogether and then no start at all.