Okay I have a very very long story... My grandfather gave me a 73 F100 pickup that he bought new. It is my first and only vehichle (im 17). when i got it, it ran very well but had a few issues. After putting around 8,000 miles on it it finally died at 150,000. my options were rebuild or replace and my pockets were only deep enough for a cheap replace, so I found an exilent looking engine on craigslist for $750 which was very risky but my only option. The engine was very nice and painted up all blue and poking around the valves and removing the oil pan i could tell recintly rebuilt, so i took it to a shop and swapped it out. Put a 600 cfm carb on it and fired it up, and it ran like crap, like the timing was way off and i couldnt get it right, after some poking around i figued out why he sold it so cheap, he couldnt get it to run either, because it had a racing cam in it, so we put a standard on it and it purred beautifully... for a bout a week, then it just wouldnt start, i eventually figuered out it had cylender wash so i put a cap full of oil in each cylender and it fired right up and ran fine for about another week. Then one cold morning (about 30 degrees) i started it and let it warm up hopped in to go to school and it just sputtered and the revs just wouldnt climb, same thing in neutral. then the next day it was warmer (around 40) and it fired right up ran fine. so the 2nd to latest issue was when it is below 40 degrees it will not start no matter what i do, the engine spins fine and will fire and cought a lot like it should start but just dosnt. but the next day when its above 40 it fires right up, very odd to me. Then ive had a battary issue i think, it seems like its dead and i use my moms car to jump it and it starts, its a new battary so i took it to get it replaced, they put there tester on it and it read a okay, i said " so it shoild start right now then" yeah it ought to and it dosnt so they get their jumper box and crank it up all the way and it slowly coughs into life. so i figure while i have it running ill drive it around a bit, ive been cruising for about 30 mins with no problem then at around 50 mph i notice it begins to lose power then a massive backfire out of the right tailpipe, then a massive one out of the left and it cuts out, i pull of the road and it wont start every time i try i see the fan move about 3 inches and it stops, try again 3 inches and stops.
I am at a total loss as to what it is but im getting frustrated that ive thrown all my money at it and am still left with a truck that dosnt run. people tell me to sell it but my grandfather is my hero and i plan to give it to my grandson when im old. being only 17 i have little money to throw at it. i have a job so i have a little but nothing extreme. so ill list everything i can about the motor.

FE 360
600 cfm
standart cam (it is hydraulic however)
new plugs and wires
newish starter
when rebuilt they put better valves and springs in but that wasnt me
new alternator

thats all i can think of off hand ask about anything and ill let you know what i know.

since im a kid i dont know everything even though i think i do, but im pretty good a researching and learning so im hoping you guys might be able to enlighten me.

please and thankyou for any ideas as to what it might be.

 

I'm no expert by any means but I have a couple of suggestions:

1. The rough starts on mornings below 40 degrees could be something to do with your choke. If you have an automatic choke and it isn't working (wide open during a cold morning) you may want to consider running a cable to it and manually adjusting it on cold mornings, until the motor warms up.

2. The backfiring while driving sounds like the timing is off. My first truck was also a 73 and mine backfired on the way home after getting my new dual exhaust installed. Sounded like a battleship had shot it's cannons through my window. Get someone with a timing gun and some know-how to make sure your timing is set correctly.

3. The weak startup could be your starter getting ready to go. Sometimes before they completely go, they will begin to peter out. That would explain why your battery checked out okay.

Like I said, I'm not a professional mechanic, but that's just a few suggestions. Good luck.

 

"Work smarter, not harder"

Know what I mean? When people don't have money to shower on their ride, sometimes they get to be better mechanics. A lot better mechanics. Why? Because when they can't afford to just keep throwing parts at it, and instead they have to know what they are doing - to divide and isolate systems, and through a process of elimination, determine the cause of the trouble remaining. Just like the repair manual instructs! Some of this stuff is big $$ (and everything is big money when ya ain't got none) so let's make sure it's really the problem, instead of replacing it only to find - that wasn't it! So you have an advantage in that sense, or at least an opportunity.

Start from scratch, step by step, system by system, don't take anything for granted. Find out what's good first. From the beginning. Does it have oil in the crankcase, that kind of thing. You'd be surprised for example, at how often spark plug wires get mixed up, and also, how decent it will still run that way. Check everything.

You can get a lot of manuals and repair books online, reprints are published of the classics. The various military branches had outstanding published courses, I'm sure these are public domain and available.

Point being you need to study this stuff first. A few tools and test equipment will go a long ways. Either rent or borrow. Compression gauge. Vacuum gauge. Tach. Test light. Voltmeter/DVOM etc. Welcome to FTE btw

 

Did you change the points and condenser? New condensers form this century are often bad from what I've read. I guess a condenser could exhibit intermittent symptoms.

 

Welcome to FTE young man.

Tedster9's post sums it up nicely.

If you can treat your truck like a project, and fix things bit by bit, you will get a huge amount of satisfaction.

You took out a racing cam, which should have come with 'heavy duty' valve springs.

The 'standard cam' would require lighter springs. Did you change them ?

Did you change the lifters ? Did you run in the cam as per manufacturer suggestions ?

When you say ''we changed'' etc, who is 'we' ?

Get yourself a Haynes manual or equivalent, then structure your project.

First job might be to check all ignition components.

E.G. Did you check the ohms on all HT wires before fitting them ?
Did you check the firing order and ignition timings.

Second job might be to check all earthing. (Starter and engine etc needs good earthing !)

Third job maybe to check all fuelling.

Your project will take time, a lot of time, but well worth the effort.