Good catch
Dave ----

 

Opinions differ, but other than a drag car or other full throttle applications, vacuum advance has ALWAYS given better part/light throttle performance than full manifold or none at all. Full manifold advances timing signifigantly at idle requiring actual setting to be much different than using ported. I may not have said that right, but best I can do

 

Retarded ignition timing might be the problem. If the damper inertia weight has slipped, the marks are useless, because they have moved relative to the crankshaft keyway. Try setting the initial timing for test purposes using a vacuum gauge, ignore the damper for now.

Also any street driven engine should always run vacuum advance. It will add 10° to 15° of additional ignition advance on top of the mechanical, when cruising on level ground. Between the two, it would definitely cause overheating. A lot of folks will run full manifold vacuum to the distributor to get lots of vacuum advance at idle, the engine will run a lot cooler in stop and go driving. If you put a light on it you'll see 30° timing or more. Not a problem.

 

Did the headgaskets get installed correctly? The water passages are different sizes to direct flow a certain way and if installed incorrectly will cause overheating.

 

Here is 1 plug from each bank:





Carb is factory autolite 2150, I rebuilt it and installed new fuel pump when I first got it in December. The head gaskets were labeled "front".

The vacuum advance port on the carburetor is producing no vacuum at idle. I found a guide to diagnosing engine issues with a vacuum gauge on google, truck was pulling 14 at idle, according to this chart the ignition timing was late, so I advanced it back to where it was yesterday when the truck was bucking and that yielded 16 at idle. To advance the timing further I would need to take the distributor loose and turn it 1 tooth. I don't understand why more it gets hotter when the ignition timing is advanced for optimal vacuum.

Here is the chart:

 

Distributor timing is set first, always with vacuum advance disconnected and plugged.

With a timing light, increase engine RPM and make sure the distributor stops advancing around 34° or 36° degrees BTDC, usually before 3000 RPM. Make sure it's all done advancing. Adjust the distributor as required to get this number, let the initial timing fall whereever it may. So long as it's below 20° that will be fine, although it may be difficult to start in hot weather due to kickback.

Drive the truck and see how it runs. A defective distributor might be "sticky" or erratic and not advance or retard smoothly. Check for ping or engine knock on hard acceleration. May need to advance distributor timing slightly 2° or so, or not, depending on compression ratio, fuel quality, altitude, etc.

Then re-connect vacuum advance to whatever port you want. The aftermarket Crane are usually adjustable with an allen wrench, 3/32"

The vacuum port aka "spark" port, above throttle plates will never have vacuum at idle, it can't. That's the reason this port is used, to allow for a steady idle. If the idle RPM is real high, it will start to tip in.

A vacuum gauge otoh, is always connected to a source of manifold or "full time" vacuum, below the throttle plates. You can connect the distributor to either port, it makes no difference except at idle, there will be a lot of ignition advance at idle though because the vacuum can will be pulled in all the way. So you'll see 30+ degrees on the damper. This is not a problem, although you may find it difficult to achieve a steady idle. Surprise! That's why ported vacuum was invented, for steady idle RPM.

Any engine needs as much mechanical and vacuum ignition advance as it will stand at all times under all conditions, just short of any ping or engine knock. It will run cooler, best power, best fuel economy etc. Running down the highway on level ground takes very little horsepower, maybe 50 or so. Engine RPM will be low in high gear, with little mechanical advance. Engine vacuum will be very high, so the vacuum advance takes advantage of this and adds in the extra timing advance required to light lean fuel mixtures under these specific conditions. Usually this comes right around 50° to 52° BTDC on V8 at level cruise. Initial + mechanical + vacuum.

 

The lower plug is way hot. Ignition timing. Can't tell so much with the upper, as it seems to be in a shadow

 

I pulled the distributor out and moved it around. I got timing to where it runs and sounds great, pulls 18 pounds of vacuum. Took the truck to fill it up, motor kicks back against the starter but starts. I went up the road about 2 miles and it started bucking again. pulled into a parking lot, temp in the middle of 'M'. It didn't want to idle itself forward. I waited for it to settle between 'E' and 'M' and started back home. I made it maybe a quarter mile and it started loosing speed going downhill. I pulled into another parking lot and now the truck will not move forward or back. The brake pedal will not move more than a quarter inch, I can feel the truck drop into gear and I can floor it and it still won't budge. It will break the back passenger tire loose if I floor it and it won't do anything in reverse. I had my wife pick me up, I'll go back in a few hours and drive it home.

Maybe the over heating issue has been the engine working against the drag off the brakes this whole time.

 

A clue! When you get it home, jack it up and see if the brakes are dragging. I drove back to work from Del Taco (about two miles) the other day, and didn't notice I had the parking brake on

 

Sticking brakes will do it too. Somebody needs a Ford Truck Shop Manual for their Birthday I'm thinkin'.

18 inches of steady vacuum is good, but "moved it around" isn't a good way to test a distributor.

Have to observe the total mechanical timing advance and return with a timing light on the damper while the RPM is spooled up and back down. The reason for this is to verify that the mechanical advance inside the distributor is working.

 

Nobody has mentioned a water pump? I've had a pump that would move just enough coolant to stay good at idle but higher rpms it couldn't keep it flowing. Just my 2c.

 

I'm unable to check at what RPM the distributor is fully advanced as I have no tach. I know it's too far advanced right now because of how it starts when warm. Still needs tweaking but it is getting closer to where it needs to be. Regardless, I believe we've fixed the overheating at speed issue with the new radiator and we've moved onto dragging brakes causing the truck to become immobile.

I was able to get back to it about 2 hours later, cranked right up and drove it home. I did notice that the brake pedal progressively gets firmer as it's driven, and it doesn't like to idle itself forward after a while. Today was the first time the truck would not move at all and the brake pedal wouldn't move. When I got the truck I pulled everything apart to repack the wheel bearings and make sure it had plenty of pad left. I think the issue lies in the front but I check the back as well.

 

All you really need is a timing light. Can't set the total timing any other way. Do it once, do it right.

 

i'm back to this, still having issues. Brakes all fixed, new wheel cylinders, hardware, and shoes out back, new calipers, brake pads, and lines out front. Brakes are a little weak but serviceable, still better than a Chevy. I'll put more attention to that after I get the overheating issue settled once and for all.

I've attached pictures of my thermostat, and port it goes into on the block. I found another thread where NumberDummy posted a part number to a thermostat that does not look like the one I have. Is the style I have possibly the culprit? Also, I thought on my 351 Cleveland in my Mustang there was a brass looking ring that also went under the thermostat. This truck didn't have a thermostat in it when I bought it. Would the thermostat that belongs in this also belong in my Cleveland? I have an issue with my Mustang getting warm at stop lights with the A/C on and I've wondered if it was the thermostat not working as it should.

I'd also like to take a moment to thank NumberDummy for his extensive Ford parts knowledge, it has helped me numerous times.

 

not the right thermostat...

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