@AZSCAWPION @4x4 Bart @yardbird @Pickupmanx2 @theastronaut @FuzzFace2 @66F250_4x4 @benbuilder @john jamieson @BarnieTrk
Hey every one.
I wanted to update you on the solution/resolution to my engine misfiring question-help!

Well, the issue is now finally resolved and the engine is running perfectly.

What was the problem? Like you all said, the carb was far too rich and it was fouling the plugs. I purchased jets for the YF carburetor from Mikes Carb- 0.98 to 0.90. The truck was originally running and sold from South Carolina- ~ 400 FT. elevation. I purchased it from a guy in Driggs Idaho, ~ 5,000 Ft. I live in Idaho Falls. After seeing that the truck was purchased in a elevation of ~ 400 Ft., I reread some of your threads and saw the question on elevation, altitude, and re-jetting. The YF carb on the engine had a 0.110 main jet size. I ended up dropping down to a .096 jet size, which is much smaller. I figured this large change in size might be because of the altitude of Idaho Falls, combined with the lower cylinder compression. But either way, dropping down 14 jet sizes solved the carbon fouling problem.

Thank you all so much for the help and wisdom. I am wiser from it.

-Very Respectfully,
Matthew Eberstein

 

Glad to hear you got it sorted out.
The beauty of these trucks is that they're simple and there isn't a problem that hasn't been solved a million times over. My biggest rules when it comes to troubleshooting is 1-always start at the beginning, 2-avoid the temptation to start throwing parts at the problem, and 3-don't just say it can't be this or that, prove it. Just because something worked yesterday doesn't mean it's not the problem today. Admittedly, I'm certainly guilty of breaking any/all of my rules at 1 (or a billion) times or another, and that's usually when things turn to s**t.
The hardest thing about troubleshooting is not becoming part of the problem.

 

Way back when I had my '72 Gran Torino Sport, I put a new set of points and condenser in. Started it up, then parked it next to the house.

I went inside and got ready to go out that night. When I was ready to leave the car wouldn't start up. I checked everything I did and found nothing wrong, but no spark.

Electricity coming to the coil, points opening correctly, ect.

I finally put the old condenser back in and it started right up. The new one worked the first start and when I moved the car, then quit while I was in the shower. Who would have thought it. And this was back in the 70's when you got name brand parts.

 

Good to hear you got it running good.
I think if we seen the plugs on the first 2 pages we would have said look at the carb as it was running rich.

About a year ago I also had a miss fire under power. It showed up when I pulled the car clubs 20 ft enclosed support trailer to a show. I even removed vacuum advance hose to dist with no change.
I went thru timing cap & rotor even changed the carb, the old one did not hold good AFR based on a gauge, and still I miss??
I pulled plugs to do a compression test and found 1 plug with a big "blob" of carbon that shorted out the plug.
New plugs and it ran like new again. In checking records it had been 28K miles since I did the last tune up so it was time.

Point is it is always the last thing we check.

BTW in one of the pictures of the PVC hose it looks like the dist. vacuum advance is going to manifold vacuum and not ported.
You may want to swap it to ported and see how it runs. As was posted modern motors use ported vacuum for dist. advance.
I run ported on my 81 with a 300 (EFI exh manifolds, log intake and ebay knock off carb) and have the base timing set to about 12* BTDC. I get a little pinging when I pull the trailer that I need to deal with but it starts so much better at 12* that 8* or even 10* BTDC.
Dave ----

 

Thank you for that. I will plug into ported vacuum and see how it runs. Good eye.

I remember going through this and looked up some argument about always going to manifold- something about fuel mileage and emissions standards. But what do I know. Well, I know I can always learn something.

Thank you again.

-Matt