Well it was a little unclear by what you wrote earlier, exactly, but when checking timing with a light it should advance smoothly up and down the dampener marks, with no chatter or fuzziness, after revving up it should also return back down to the same value each time i.e. no sticking at a different spot. Distributor is the mechanical "brains" of the ignition system so it has to be functioning smooth in both directions, from idle to 5,000 RPM etc, or it will cause lots of trouble. If it's real bad it might knock badly, or maybe be gutless and overheat, or it may just be a puzzler and run erratic with poor idle or a miss that's hard to pin down.

 

Hmm... that could be my problem then . My timing mark was all over the place. You could barely watch it advance with the engine because it was never standing still ,I would say it was chattering like you said . It was worse at idle.

 

Guess it's time to bite the bullet and yank the distributor to see what condition it's really in.

 

I’ll see if I still have a pic of the distributor gear on my flash drive when I get home tonight from when I had it out this past summer. I’ll post it if I do

 

If your timing mark is all over the place it'd have to be an old timing chain or LOTS of slop in your distributor. Take off your distributor cap, turn the crank by hand with a wrench until the distributor rotor starts to turn. Stop and now turn the engine backwards. The rotor should immediately begin to turn backwards...any delay means your chain is stretched and the number of degrees you turn the engine before the rotor starts to turn the other way is how many degrees your timing could be off at any given moment. Get your timing spot-on and then your problem can only be fuel or vacuum related. Worse case scenario is that your chain is so loose that your engine hopped a tooth or two and threw your cam timing off....
Vacuum is easy. Disconnect all your EGR stuff and any power brake hoses one at a time and see if anything changes. If you pull a line off and the car runs the same, that line or component could be bad.
If your timing is good the truck should run...then get out your vacuum gauge and adjust the carb for max vacuum...maybe just a tad rich and you should be good. Backfire out the rear means you're too rich...timing is too late...or your cams are miss-timed. I bet your issue is timing...especially if your timing is all over the map...it should be dead-on.

 

Embrace the power of "and". That's also why it's important to start at the beginning. Since we can only guess the condition from here, a step by step method makes even more sense. A cylinder compression test. If the distributor is all worn out, chain stretched, the engine is probably (mostly) lunched. Getting there anyway.

 

Thanks braol I have checked all my vacuum lines and they make no difference in the way it runs . I don’t have a vacuum gauge so I could only guess on the carb if I tried that . I just checked for the loose timing chain . Standing in front of my truck looking towards the back of it I turned my engine clockwise and the rotor moved immediately, then turning it counterclockwise there was a lot of play. Probably pushed my 2ft breaker bar 6-8in before it moved my rotor.


This is the only pic I have of my distributor gear

 

Well, it sounds like a timing chain issue. It's not hard to do, just make sure you follow the manual and ensure your cam/crank marks line up. A new chain is cheap insurance regardless and will allow you to cross one more "cause" off your list.

KEY TIP: When setting your initial timing...make sure that your vacuum advance hose if disconnected from your distributor canister....

 

Ok I’ll probably look into shop prices just so I don’t have to spend a day out in the cold , but I might have too. Thanks for everyone’s help and I’ll post and update once there’s something that needs updating

 

Your timing marks floating all over the place IS the bad timing chain and gears. Along with all your other symptoms. A Dizzy that loose to cause marks floating that far would be real noticeable up top. I've never seen a Dizzy worn enough to cause timing marks to be 2" apart. You prolly did a foot to the floor higher RPM jaunt then backed off the pedal too fast and too far. On an old factory timing set this can cause the nylon teeth on the cam gear to get messed up. Do yourself a favor and DON'T get cheap when you buy a new timing chain and gears assembly. The camshaft and the crankshaft must be timed together correctly. So the alignment marks on the cam and crank gears must be stamped in the correct spot. The marks on cheaper sets can be as much as 6 degrees off.
I suggest buying Cloyes brand timing sets. And still not their cheapest set.

 

Thanks Jefffafa, As far as high quality goes with cloyes timing chains. It seems like they are more categorized for different applications rather than a cheaper and higher quality one. They have a heavy duty and street billet style that could apply to me. Idk the difference between the two .

http://cloyes.com/Images/CloyesHP2017.pdf

This is the link to where I was getting that info . If you get a chance to take a look I would appreciate your opinion on which one you would suggest

Thanks

 

The Street True. Note how the alignment marks are supposed to be lined up when you install this set. 1st thing you do before tearing the front cover off is spin the engine around until the external timing mark is at "O". The engine spins easier with the spark plugs removed. Then take the cover off and check the gears. Especially the cam gear. The marks are supposed to be lined up like the pic on that site you mentioned.

But the cam will prolly be shifted to one side or another because of the slop or nylon teeth gone. Spin the cam and gear to align the marks. Then swap out the timing sets.

 

Sorry I should of mentioned that I have a 390 . They don’t have a street true listed for the 390 . So I would have to be a heavy duty or street billet . Ik I’m in the performance catalog but they didn’t have any 390 parts in the stock replacement catalog . Also thanks for the removal tip. Can I get the job done with standard tools or is there anything special I should buy ? I was scanning my manual last night and saw something about a special tool to get a sleeve off ( mabey crankshaft sleeve if I remember right )

 

Get the Cloyes set with the steel timing gears: On the Summit website: Cloyes Race Billet True Roller Timing Set, # 9-3608X9 It says "racing" but it is the same as the regular set...except it is all metal gears. If you were to go hog-wild you could get the set with the hex adjustable timing to really dial in your cam timing...but that really is just overkill unless you really are racing your truck.

 

Awesome thanks . There were two it brought up Only difference is one is Block Align Bored and one isn’t . What is the difference? As for racing my truck ... I can only pretend