Hi everyone,

I believe this is my first post here. Hello!

I recently acquired a 1971 F100 with a 302/C6 and so far it has been a great truck. It ran really well when I first got it, but all of a sudden it started giving me problems, particularly with idling.

The truck has a 302 out of something later, probably early to mid 80's f150. It has a Holley 2300 2 barrel 500CFM carb on it as well. After an incident that revealed there was no fuel filter, rebuilding the carb, then trying a Motorcraft 2100 on it instead with the same results, we found the intake manifold gaskets were bad. Replaced them and now it runs ok.

Now the problem comes in setting the timing. We loosened the carb and tried to advance the ignition. When we did, nothing happened, the idle didn't speed up. When we retarded the ignition, the idle slowed down a bit and started running like crap like it should. Idle mixture screws do nothing to the idle. We just kind of set the timing by ear and think we got it about where it wants it. We can't really put a timing light on it as this engine is a hodge podge of parts and the front accessories block the view of the pointer. What would cause there to be no change in idle speed when advancing the ignition?

There is also another problem that started shortly before the intake manifold gaskets went bad and continues to be a problem. When started from cold, it will die unless you keep it wound up a bit. If you just try to keep it at even about 1500 rpm, it will just slowly die. You have to keep it about 2000 rpm for about 10 seconds, then you can slowly lower the rpm's until idle and then it will hold idle just fine. When it dies from this, it doesn't want to start back up until you pump the gas. I replaced the fuel pump, with no change and the glass fuel filter I installed has solid fuel in it.

 

Hi,

"We loosened the carb and tried to advance the ignition. When we did, nothing happened, the idle didn't speed up."

I hope you meant to say that you loosened the DISTRIBUTOR not carb.

Anyhoo, Did you have the vacuum advance line removed from the distributor and plugged when trying to adjust base timing?

If the idla mixture screws are not having any affect on idle.... this usually means that the throttle is not closed all the way at idle. This could be due to the idle speed screw holding the throttle plates open to far. This takes the carb out of the "idle phase" and into the "cruise phase" where the idle mixture screws have no effect. Try lowing the idle rpm first with the idle adj screw. You may have to play with the timing also to get the idle down to where it should be. Once this is achieved hook up a vacuum gauge to manifold vac and adjust the mixture screws for the strongest vac signal.

As for the cold start problem. It sounds like the choke is not set up and working. I would validate/adjust the choke.

hope this helps,

 

I think I may have just found some of the issue. I don't know if this is normal or not. I can rotate the rotor shaft about 10 degrees or so, and the little bracket the points and condenser mounts to moves around quite a bit.

I took a video of it here:

 

2X the above statements, Also, to me, it sounds you may have a vacuum leak. if you can get to idle okie dokie, spray WD-40 around the carb. carb base, anywhere vacuum me be generated.
You can also set or check you TDC timing. #1 piston all the way up on a compression stroke. Pull plug when it blows your on compression. piston up, remove dizzy cap nake sure rotor is pointing to #1 plug wire.
"Sometimes you have to slow down to go faster" Richard Petty 1978
"Sometimes you have to back up to forward" Me, just now.

 

It's a lil loose but not ALL your headache. Change points and condinsor 1st!!!!

 

Truck idles real well now, but does seem to have some hiccups when driving.

I sprayed around everywhere I could with some starting fluid and it didn't have any effect. I also tried around the vacuum modulator under the truck.

I took it for a drive yesterday down the road and it hesitated shortly after accelerating, not like not having enough accelerator pump, but like it lost fuel or spark for a second. About 10 feet later it died. Started right back up and didn't die after that, though. I just backed up back into my driveway as I live in a relatively busy area and didn't want to risk breaking down in the middle of traffic.

Should that bracket have that much play in it? It would seem like the cam on the distributor shaft can't open the points at all as the bracket has too much play in it.

 

The rotor movement of ~10* is normal. That is the distributor's centifical advance. Notice how you twist the rotor and it returns back under spring tension when you release it.

The springs control the rate that the timing increases as RPM increase.

 

Get a vacuum gauge and learn how to use it. Cheap, easy to use and the best diagnostic tool around: Takes the guess and by golly out of the equation.

 

Where are my manners?!
Welcome to FTE!!!

 

thanks for the update. What did you do to make her perform better?

 

The truck idled pretty good after we changed the intake manifold gaskets, the problem I was having was advancing the distributor had no effect on idle quality or idle speed.

I think it at least needs a new breaker plate. The pivot on this one has so much play that when the cam comes around to open the points, it will just push the whole points to the side instead of opening the points. I assume it runs because when it is spinning fast enough it can use physics to open the points a bit without moving the breaker plate. When the engine is running, there is a distinct knocking sound coming from the dizzy that I can replicate by wiggling the breaker plate around.

 

10-4
Have you adjusted air/fuel screws?

 

I don't think I've seen a dizzy do that and I've had some really bad ones. See if the mounting screws are tight. (for the points) or add electronic breaker such as pertronix.

 

Well, its running a lot better now.

The Motorcraft 2100 wanted about 5 turns on the idle screws to keep from dying while idling before we changed the intake manifold gaskets. After it still wanted about 3-3.5 turns to idle which is still way too much. I also noticed if you wing the throttle, it wouldn't idle afterwards no matter what you do (play with the throttle, idle screws,) but it will fire right back up and idle.

I took the Holley 2300 I rebuilt and thought was just completely wore out and put it back on, and it runs much better. It doesn't have those random hiccups idling anymore and only needed about 1/2 turn of the idle screws.

 

Great!! Now tune it with the vacuum gauge.