Timing.... It either bogs or wont start

[1986F150Six]

Too much timing advance. And stumbling with two different carburetors??? It seems that the distributor is the common denominator. Does it have a designated 12 volt power source with heavy enough wire gauge to support the demands of the GM type module? Is there a relay?

I would try to find another distributor and swap to see what happens.

[asdfghjkllkjhgfdsa]

It's coming directly off a switch that's run back to the main solenoid in 10 gauge wire. No relay. That probably isn't it because it wouldn't be intermittent or increasing as driving went on. Plus the wire isn't hot/warm to the touch so it's not drawing to much current.

I think your right about the distributor being the problem. And too much advance. But when I try to turn it below 30 degrees it starts to stumble really bad at idle and any lower and it just dies. Pity if the distributor is bad. Looked pretty new.

What did I do when I opened it up that made it be stable at 14-16 degrees to now not getting lower than 30???

[mat in tn]

this dist certainly does NOT look new. if nothing else. you might even get a new one of the same type. and wire it on a relay circuit. all the module and or coil have to do is get voltage starved and start heating up or even start heating up the weakest link in the chain. if you could post a picture of the camshaft it would help us determine whether it has been run or not. and measuring a lobe or two will let us know which one it is, however, you are getting good vacuum. you are achieving good rpm both in and out of gear.

[asdfghjkllkjhgfdsa]

This is the cam that came in the box, obviously not the one that's installed. My calipers say a love is 1-22/32 wide

[mat in tn]

excellent. that is certainly a used camshaft.
measure the widest point of the cam lobe. then measure the smallest. subtract the smallest from the largest and this will yield the amount of lobe lift. lobe lift multiplied by rocker arm ratio will give you valve lift (opening). of course this is best done with very accurate micrometer or digital caliper but just do as close as you can.

[asdfghjkllkjhgfdsa]

The measurement I got on the cam lobe was 1.708 height 1.465 width for a ratio of .243. The box again had this info:
                    Adv Dur 268,268
                    Dur @ .050 219,219
                    Lobe Sep 110 deg
                    Valve lift .456, .456
So if the measurement I took doesn't match the box info then the new cam was installed and the old cam is what was put back in the box ( IE what i measured) If that is the case, is the new cam (the one that is installed using the box numbers) considered a "Heavy Cam"?


Also back to the hesitation off idle/engine stalling situation I am having. So if I do have a heavy cam, then from what Im reading it pulls less vacuum at idle. This means you really have to back-out the idle set screws and push in the curb idle screw to get a good idle (Which is exactly what I've had to do to get it to idle). From my reading this means the transfer slot is open to manifold all the time and you don't get that smooth transfer from idle to low rpm. I still not sure why this means its a "Rich Bog/Hesitation" but it does seem that too much fuel and not enough air is getting into the system at off idle conditions. (and yes I have checked my accelerator pumps, they are good and quick to squirt)

The solution I've read about is drilling a small hole in the throttle plates (1/8" or less) to allow more air flow but still let your plates be mostly closed over that transfer slot. Since I've had this problem with two different carburetors, each needing the idle screws set extremely high, would it be safe to say that I am not getting enough air and this is the cause of my bog/hesitation and not the timing? Should I drill these holes?  

[ArdWrknTrk]

You've got a hot cam with too much overlap.
People like the sound of a choppy idle, but it makes throttle response like an on*-off switch.

You have the stock cam.
Put it back in, and the truck will be everything you want of it.

[85pig]

The 268H isn't a terribly large cam, but the Comp grinds are known for detonation in the 300 (their timing events raise the dynamic compression pretty high).  Why I'm surprised your engine doesn't ping under load.

As Jim mentioned, the stock cam should bring back good drivability.    

[asdfghjkllkjhgfdsa]

Unfortunately I don't have the area or the knowledge to replace the camshaft... Don't even have an engine hoist.

Is there a way to mitigate the off idle hesitation. I mentioned I read about drilling a small hole in the butterfly as an option. Thoughts? Also what would be the best timing for a cam such as mine

[ArdWrknTrk]

Can you pull the radiator and do it in situ?

I'm no kind of expert with the 4.9-6 so I will leave that to others.
But I definitely wouldn't butcher my throttle plate, because while it isn't a "big" cam the valve event timing is all wrong for what you want.

[85pig]

That's doable with the 300.  Obviously kind of a pain (and guiding that 10 foot long cam back into the block would be fun), but it's an option.  If a guy was to do that, he could also see if the previous owner used an offset cam key to bump the timing up as well.