Hi Everyone. I recently purchased a 1976 F100 long bed off craigslist. I have since joined this forum and have been looking around and it is great to see everyone's trucks and input!

I do have a question as I am very new at working on engines. I am mechanically inclined, and can generally figure things out, but I am currently stumped.

My truck has been running for a month or so completely fine, and one day decided to idle pretty low in park(1000rpm vs about 1300rpm normal), then stall out as soon as I put it in Reverse or Drive.

I have been working on this issue for the past 2 weeks, thinking it was a vacuum leak (by using the carb cleaner spray and listen method), I checked the hoses, and replaced the carburetor gasket. This did not fix the issue, and am currently trying to figure out what is wrong.

I purchased a vacuum tester, and hooked it up in idle. The needle was bouncing between 14 and 16 mmHg. I know 15 is a little low, but I believe the guy i bought it from said it was bored and cammed, so I do not know if that makes a difference. I also know the bouncing needle can indicate an issue, but I am not sure what.

I also just replaced the spark plugs b/c they looked pretty bad.

Can anyone provide some sort of guidance as to where I should look for issues? I have tried searching the forum for similar issues, but I cannot seem to find anything.

Some info on my truck is below.

302 engine
possible aftermarket cam
C4 Automatic Transmission
Edelbrock Intake
Holley Street Avenger Carb



As I get a little more knowledgeable about engines/diagnostics, I am happy to return the favor

 

Here are some pics. Just for Fun!

 

Check and make sure your distributor hold down is tight and it didn't get bumped out of time or rotate a lil from being loose.

Sharp looking truck.!

Oh yeah, and welcome to the club too.!

 

WoW, very nice looking truck.
X2 on the timing.
With the cooler weather, use you vacuum gauge and check the air/fuel mixture as well.

And welcome to FTE

 

That is a very interesting looking (and sparse) engine compartment! Firewall, inner fenders, rad, etc. wrapped in .... stainless steel? Hiding all of the wiring and hoses?

 

Nice truck, nice color, nice eng bay. Sounds like a carb/vacuum or possible elec issue, and you are on the right track to find it. So you do not need a heater huh?

And since all the a/c lines and the heater is not hooked up, you might as well removed the complete box...and really slicked the firewall up.

 

Thanks for all the guidance and positive responses.

The engine bay I am assuming was done to hide everything. Kinda makes troubleshooting difficult due to it being riveted on I bought it thinking if the paint and the engine bay are in this good of shape, the person that built it must have taken very good care in building the engine as well.

I am in FL, so a heater isn't really necessary. A/C would be nice, but that is an adventure for the springtime.

I found a timing light on craigslist today for $5, so when I get a chance away from work, I will adjust it and report back!

 

I got it running!

Thank you all for your help. After a week of rain and a week of tinkering, I was able to get it to run.

The timing light I bought off craigslist worked for a few minutes then worked intermittently, so I will fix that and adjust the timing for with it accurately when I get to it.

I noticed the vacuum advance was plugged into the full manifold vacuum, so I hooked it up to the timed vacuum port on my carburetor, and adjusted the timing by ear. basically whatever minor rotations allowed for the engine to run better. It ended up delaying the timing just barely off the existing timing (I had the vacuum advance plugged for this).

I then read in my carburetor manual how to adjust the idle mixture/speed. This helped immensely. By adjusting this, I ended up backing out the idle mixture screws about 1 full turn each by the end of it, adjusting the idle speed screw to stay constant (about 900RPM) during each 1/4 turn. It was then at the highest vacuum I could get, and I was able to put it in Drive without stalling out.

I think this fixed my issue, I just have a little off-idle stumble I will be trying to address.

Thanks again!

 

Most excellent!

The more you learn, the better off you are.