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over the past year my 1963 F-100 Unibody with the 223 has been running pretty rough. Its not even drivable right now. I am trying to diagnose the issue now, but I feel as though I have tried everything. For the fuel system I have redone the tank, all new fuel lines, new filters, new pump, new carb. For ignition I have replace spark plugs, tested all of them, measured the spark plug wires, and pertronix electric ignition. It idles pretty well, it hesitated/stalls when the truck is under load or is braking hard. It sounds to me like it is starving for fuel. Is my float bowl maybe misadjusted? I also am looking at replacing the vacuum advance, but cant seem to find the replacement part online. I took a picture of it (attached).
Would you guys be able to help me narrow down my trouble shooting? I feel like Ive tried everything I know, I may have replaced the vacuum advance at some point... it says "Made in Mexico" on the back
Have you done a compression test?
What carburator are you using now? And does it have one of these in it and is it working? Holley Spark Contorl Valve (carburetor-parts.com) All the stars have to align perfectly for that Load-O-Matic distributor to work correctly. If not, you will have all sorts of drivability problems.
Thanks for the reply crop duster.
I have the AutoLite 1100 unfortunately, and I have not done a compression test. The AutoLite that I have does have a spark arrester, but on the Holleys isn't that part called a power valve?
How could I do a compression test? do they rent the tester out at auto parts stores?
I always do a compression test on any engine that I don't know the history of. It will give you a good indication of how healthy it is. AutoZone or O'Reilly's rent those testers. It should have instructions with it. I usually run the engine until it's warm, pull all the plugs, disconnect the coil, block the throttle wide open, then go about 5 or 6 hits on each cylinder. Don't forget to write the numbers down.
I Can't say for certain that your SCV is the problem, but it is easy to change out.
A spark control valve is not the same as a power valve even though it looks like one it doesn't work like one. If you scroll down in the link, I posted you will see all the carbs that valve fits. Also, at the bottom there is a pretty good explanation of what it does. Without typing a book on trouble shooting a Load-O-Matic the easiest way to check the SCV is to just install a new one and see if it changes things. The vacuum signal from the SCV to the distributor is very small and requires a very sensitive gauge to read.
The compression numbers look OK. You can't really tell much about a spark plug if the engine has been idling very long before it was shut down. I see you have platinum plugs. These old engines really prefer regular old copper core plugs. The platinum plugs are really for these new engines that run a lot higher combustion temps than any of our old junk. The only thing that stands out on the plugs is #4 and #5 are showing a little too much spark advance. The color change should be right in the center of the curve in the ground strap.
Thanks for the speedy replies Crop Duster. I have a couple of questions. Should I consider going back to copper plugs? Or just just next time I replace them get the copper ones?Is 3psi a good reading for fuel pressure? Only numbers I can find online say don't surpass 5psi.Would spark plugs 4 and 5 point towards my vacuum advance working too much potentially? What could cause the over advance? Thanks so much for the help!
Just keep the plugs you have for now. Book says 3-1/2 to 5-1/2 psi fuel pressure for a 223. I don't have a shop manual for a 1963 truck and those Load-O-Matics were tuned by the factory for each different vehicle and transmission combination they were installed in. It almost requires a distributor machine to really dial one in.
Your shop manual should have the specifications for your truck.
This is the specs for a 1963, 3 speed car.
Initial timing 4 degrees BTDC
Inches of vacuum to begin to move the diaphragm 0.3
Maximum advance 26 crankshaft degrees @ 10 inches of vacuum
After a little bit of a break I came back to my truck to see if I could get it running well before the summer. I did end up doing a vacuum test and found that that at idle I was getting about 0.3 on my vacuum gage (guessing it's inches not psi). With the vacuum advance disconnected to put the gage on, I was only able to get up to 2(inches probably) with high revs before it bogged down. I am starting to wonder if I have a vacuum leak like what was mentioned earlier. How can I efficiently check for this? I've heard of people spraying starting fluid on the intake manifols while at idle. Is there a better way?
Wouldn't manifold pressure have to be below the throttle body? Since it is an AutoLite 1100 it doesn't use manifold pressure, it uses venturi pressure I believe. please correct me if I am wrong.
As stated, you have to check engine vacuum below the throttle plates. The reading you are getting is the vacuum to the distributor thru the spark control valve. Which at idle should be about what your gage is showing.
