Hello, finally registered after reading for a bit.

So I bought a 71 f100 302 C4 early this year. It would not stay running and the guy was tired of messing with it. When he started it I could hear the massive vacuum leak and knew that was the culprit. Got it home and a little carb cleaner confirmed a big leak on the back side of the carb. Gasket took care of it.

Well, here I am 8 months later at a loss. I've read a ton of threads here and on other sites and am not sure where to look now.
As soon as it goes in drive or reverse it dies. Sometimes it will stall after idling for 20 minutes or so but not every time.

Idle rpm - not sure as I have no gauge. Going off sound it seems to be close to right. I have also tried lower and higher with no change in the stalling issue.
Vacuum - 15-16 no leaks to be found
I've played with timing, 10-15 degrees, and is currently set at 12.
Carb has been rebuilt and functions properly.
New fuel pump with 6 PSI going into the carb.
New plugs.
Dist and vacuum advance check out.
New fluids, nothing alarming when I changed them.

Outside of the above, I have done nothing else and have no other knowledge of the life of this engine.

Oh, and as of tonight while rechecking the above numbers I noticed a light tick from the front of the passenger side valve cover. Never noticed it before. Engine was warm and did not change sound with rpm.

I've read that a loose or damaged rocker will cause performance issues and in rare cases cause the engine to stall. Could this be the culprit and has just gotten progressively worse? Or do I have a separate issue?

I've got to read up on checking the rockers and such and will pull the cover later this week to look further into the tick.

Any other ideas of what to look into?

 

hawk3048, Welcome to FTZ. Does it always stall when you put it in gear?

You Said, "Sometimes it will stall after idling for 20 minutes or so but not every time". Is this idling in Park or Neutral and it just quits, shuts off by itself?

More on the low vacuum after your responses, Cap

 

Everytime it goes in gear.
It will idle in park or neutral. When it shuts off it's instant. Not like a running out of fuel deal. Which makes me think electrical but I'm not sure what else to test

 

I would look at the coil and possibly the little wire from the coil to the distributor . Look for cracks in the insulation. I agree that it’s probably something electrical. Coil could be going bad and cuts out after it gets hot

 

I would look for a vacuum leak, possible crack in a vacuum hose.

 

hawk, I'm gonna go out on a limb with this. Will need others comments on this. I'm thinking something in the Torque Converter has failed and may be locked up. Instead of slipping when at idle when you put it in gear, it just abruptly kills the engine dead.

Is this 302/C4 the way this truck left the factory or swapped into your truck? Cap

 

I have sprayed around all gaskets and the few vacuum hoses. No audible or visual change so I think I have the vacuum leaks fixed at least on top side.
I also checked vacuum again to in the daylight (the lines between 15 and 20 are barley readable so I couldn't see them good the other night) its actually 16-17 at idle.

Would vacuum while idling in drive ( the few seconds that is does before cutting off) give any clues? I looked at that today as well. It is 14-15 and very jumpy.

 

I believe it to be the factory combo, however not sure if it is the exact same that came in it or any rebuild info on either one.
I had read about that and considered it. Also saw mention once that the c4 doesn't lock up. I'm fairly decent with most stuff but do not have much in the way of trouble shooting transmission related issues. What would be the best way to confirm a TC problem?

 

Is the engine idling high? Vac should be around 20
If it’s a later model engine with a egr valve behind the carb, the plate under the carb could be burnt through and leaking. Also try unplugging the brake booster and cap the hose see if you have any change

 

So I bought a gauge today and it idles in P/N at around 880. When I did the carb the plate looked good. Unless I am missing something glaringly obvious the truck does not have a brake booster. Currently waiting on youtube to upload a video so that it may be easier for everyone to see what I have going on.

 

You said the plate looked good, so does it have an EGR valve behind the carb? If so the valve itself could be bad . There would be a separate plate under the carb with the valve attached and would have a second gasket under it . Between plate and intake.
I think if your vac reading is only 14-15 you have a leak some where and you will have to eliminate each connection. There should be a connection on the back of intake going to the vac modulator on the transmission, rubber hose on each end could be cracked

 

https://youtube.com/shorts/DZswt9boZYo?feature=share

https://youtube.com/shorts/a9TGBH504rE?feature=share

So the above links show it idling and the restart after it cuts off. Some times I have to rev it a little or it will not start back.
this shut off is the exact same as when I put it in drive.

also the plate was good when I did the carb and the truck does not have a brake booster

 

Line runs from plate to the PVC on the valve cover. All new line and pcv. New line to transmission. Currently headed to parts house for a transmission modulator so I can rule that out

 

The only other place I can think of to look is the intake sealing area, check it like you did with the carb base. I had a 70 -302 that previous owner had shaved the heads but not the intake, which created a bad angel onthe intake sealed by surface and a leak.
I still believe there is a leak somewhere, since you only have 15 on vac gauge

 

No further comment from me at this time on Torque Converter thoughts. Resolving the other issues being discussed now as the cause first.

Again some thoughts,
Thinking 71 would still have points n condenser ignition, that cap looks not typical Ford points system, suggesting it is electronic ignition?? The point set up would have had built into the harness, a resistance wire for reduced voltage to the coil and points. Could that wire be powering the apparent electronic ignition and not giving full battery voltage??
Did you do a check to see if the timing chain might be badly worn, being a cause of low vacuum at idle??
Are you able to get the idle down near normal to check your timing with the advance line disconnected and plugged ??
Curious about the year of the engine, maybe the # on intake manifold, beginning like, D1 being 1971 could tell.
Is the EGR valve talked about hooked up??
As "RP67F100" mentioned the EGR mounting casting between the carb and manifold, the castings made of aluminum or a pot metal have been known to erode away inside and allow exhaust to be sucked into the intake creating a major vacuum leak. Cap