Dave...I appreciate all your comments and you seem to know as much as me times 100. I know a little and DC is the easiest to understand but you just confused me... which is no great challenge the older I get.

First...I understand heat soak... and that 460 is a heat building monster.. I wonder if I use an IR temp meter if I could get an accurate reading of the fuel temp thru the site glass ?? Would temp readings on key
components i.e. carb base, alternator case, intake manifold temp. what else?? show anything ???
remedy is in the brown truck arriving tomorrow i.e. 1" phenolic spacer & gaskets.

Gas Brand... since the 460 drinks like a room full of Alabama fans... I've filled up with Citgo premium, Shell premium and Chevron premium (all 93 proof) and have had the problem
with all brands mentioned... so I'll push that further down the list.

Charging but not charging.... I'm totally lost here. If the alternator is making juice at the o/p terminal and there is a sufficient sized wire leaving there back to the battery... what would
impede the electricity from just running up the wire to the battery...said wire being #2 fine wire cable (low resistance) When I check voltage at the alternator bolt I read 14.25 volts and
I check voltage at battery + post... that's through less than 4' of #2 wire... I read 14.25 vdc... I see no voltage drop so I'm assuming cable is good (my meter won't read hundredths of volts
It seems to me that the battery is seeing the 14.25 volts that the alternator is putting out, right

the sense wire??? I got a ground from the alternator case to the frame 5" long #4. I've got the #2 wire from the alternator o/p to the battery... I got no "sense" wire and nothing goes back
to the cab other than the wire to the voltmeter in the dash...so I'm still confused

Higher o/p- alternator was only suggested IF the 100 amp I have doesn't have the capacity to handle the full load of the truck...I don't think that is the case. Somewhere I have a 100 amp dc
amp meter I might jury rig into the alt circuit and see what the actual draw is with everything on...a/c,lights,elec fan, hood actuators,etc. I can't imagine I'm pulling over 50 amps at most. (surge maybe
but not constant load)

The tech at CVF Racing ( alternator vendor) is sending a smaller pully for my 100 amp alt. That should at least get me charging at a lower rpm... I idle at about 700 or so and the alternator doesn't kick in till 1500-2000 as it
is right now. So a long idle time with a/c on for instance might give me a drain but I don't think it would get battery below distributor operating threshold, do you ?

BTW my parasitic draw is like 0.02 amps

Hoping you can lift the fog and educate me some more... this shouldn't be that hard...considering you only have two or three problems that could give me the results I see..

thanks
john

 

John , are you getting your 14.25 volts at idle ?

 

Is the 14.25 with everything turned on? Try turning everything on, engine fans, AC, headlamps, idle in gear foot on brake then check voltmeter does it continue to drop slowly? Just asking.

 

ok., been busy with other crisises... but have replaced elec fan motor (that's another problem that showed up.

put on the smaller alternator pully
added phenolic spacer 1" under carb

volt readingss
battery with all off 13.4
battery with engine running (first started) at 1000 rpm (high idle) 14.7
battery with all accessories on 14.2
battery with all accessories on and in gear (700 rpm) 14.0

did not show signs of dropping in 5 minutes/.s.

temp readings after engine at temp intake manifold (aluminum) 160
carb body 130

never took readings before spacer added

Will take for a cruise after lunch... right now cool off and eat a sammach

john


and later that same day...

went for a cruise..10 miles surface roads and 30 miles on freeway... it acted sorta right, temps stayed good... voltage stayed above 12at idel 13-14 when crusin

as I got off freeway returning home... it started the stumble/die thing... started up ok and as I gave it gas off idle..it backfired thru carb,,
died.started right up running rough almost like a miss.
I limped home with the same problem at stops .. accelerated from stop it would stumble and backfire then ran with a miss

got home and checked temps intake 185 and carb body 145... water temp 200

I'm about to believe it's deeper in the ignition... since it backfired that means there is gas getting in carb/engine

gonna call DUI folks and see what they say... what are the symptoms of a dying module in the distributor ??

suggestions ???

john

 

Not really, a backfire is when the ignition fires incorrectly to a cylinder were a intake valve is open.
Maybe just what you have.

 

In my experience electronic ignition modules either work or they don't, there is no intermittent failing unless it's bad connection in the wiring itself or a connector seating type issue.

I'm probably the only one but my money is still on a vapor issue.

Jim

 

Old GM HEI's in the 80's were notorious for acting up when the they got hot. I saw it a lot when I worked at the speed shop. It was almost always the coil in the HEI cap would short to ground when it got hot.

And to the backfire issue, it can also happen on the exhaust cycle, unlike posted above, so the question is is the backfire through the intake or exhaust?

 

I would lean towards heat affecting your ignition system .

 

Dave backfire is thru carb
Scott..l. engine temps are noted above...l did not take temps of the dist or coil
F1... I agree with your statement, but if there was no fuel there would be no backfire, correct??

 

Stupid question... Do you have full battery voltage to the ignition? Those distributors don't like low voltage, I have seen the resistance wire or ballast resistor from a points ignition used to power the distributor, without good results. If you suspect a voltage drop at the distributor, you can temporarily run a wire right from the back of the alternator right to the distributor for testing.

 

My money is on a faulty distributor , do you have anything to swap with it ?
Even an OEM unit .

 

nope, Scott... gonna get a call done to day to DUI Performance Distributors

I've got some resistance and voltage numbers to check coil ...hopefully get that done today

I got corrected on another site... not a backfire (with actual fire) but a 'cough' ( mist of fuel) back thru carb.. More of a 'chuff' than a bang sound

john

 

I had a similar probelm. My module would fail {maybe 4 months maybe 6 months). There is a world of differences in electronics out there. Don't buy cheap, find and buy quality(hard to do). If you replace module maybe try NAPA (Ecklin if they have it). I ended up replacing distributor. Only been 3 months so still have fingers crossed. Good Luck.

 

Hey John,
Could you do a voltage drop test between your battery positive terminal and where you coil connects to your IGN voltage? Just like testing your battery voltage, but you don't ground the negative test lead, it just connects to where your coil is fed its 12 volts right at the coil wire or terminals. If it shows more than 0.25 volt or so it will indicate excessive voltage drop to your coil due to a high resistance coil wire, too small of a coil wire, bad connection, bad ignition switch terminals, or bad IGN switch contacts. Try turning your IGN on and off a few times to make sure your voltage drop is consistent.
Just something else to look at.

 

John, through the intake cough/backfire, what ever somebody wants to call it, is usually caused by some type of pre-ignition event that cause the incoming air/fuel to ignite early while the intake valve is still open. This can be caused by several different things, a hot spot in a cylinder, faulty ignition, burnt intake valve, a bad spark plug that is burning hot(wrong heat range) etc... I can't remember but I believe your engine is fresh so there should be no carbon build up causing hot spots in the cylinder. I would lean towards something in the HEI distributor and it would hurt to take a look at your plugs as it might point you to a particular cylinder with an issue or eliminate that as a possible cause.

As far as the running rough vs a miss, running rough, as in all cylinders, that could be a lean condition as a lean condition can cause a lean miss fire. But I, like several on here am leaning towards the ignition system.