[shaker455]

Good point Steve and that's why I suggested pumping some into a container and time it.

[Stripes]

Looks like it's fixed, drove it a few hours with no issues. The steady cruise occassional sputter is also gone. I swear it felt like a fuel issue. You could drive it 20 mph and push the throttle more and it would slow down. But if you opened the second aries it would surge ahead briefly, like the primary bowl was empty. So weird. I had installed a new module, cap, rotor, and coil when this first started. I had never seen a pickup coil go bad like that, thought the worked or didnt.

[shaker455]

I've had cars since HEI's was a new thing.
Very reliable, BUT when the module goes bad they can be misleading.
Years ago when I 1st put an MSD HEI module in my car I was out cruising a back road one night and the new module crapped out!
Good thing I had the old one in the car!

[Stripes]

Yesterday, we drove the 69 FB on the highway (at 60F outside) doing 70 mph at 2000rpm. At mile 30, suddenly the can began running poorly and we coasted to a stop. The water temp was 165F, AFR 15 to 1 at cruise, fuel pressure showing a steady 10 pounds.(which is too high but I dont believe the guage for the mechanical only pump). Felt carb and fuel lines, they were not hot. Waited 10 minutes and restarted the car and drove 4 miles more to the pontiac party. 5 hours later we left the party. We made it about 5 miles. Coasted to a stop, engine idles but wouldn't take throttle without wanting to die. Shut off engine, wired new hei direct to positive battery terminal, and drove home 70 mph the remaining 29 miles.

Is that the problem? Who knows at this point. Going to wire a light to the positive hei lead and tape it to the windshield. Then I'm going to wire the hei direct to the battery and drive it till I'm walking again or I make 50 miles.

[shaker455]

Go back and read post # 37

Again, do you have it wired on a sole full 12 volt source and confirmed while running?

If so: Try "just" a new Module & correct insulating compound

["QUICK-SILVER"]

Originally Posted by shaker455

Are you running your HEI on a sole 12 volt source rather than the factory points wire?
FYI: 69' model year also has resister wire in the dash as well so check your running voltage

Originally Posted by shaker455

Go back and read post # 37

Again, do you have it wired on a sole full 12 volt source and confirmed while running?

If so: Try "just" a new Module & correct insulating compound

This needs checked out for sure.

HEI will crank and run with the factory resistance wire in place. Amps required for the HEI will get the resistance wire very hot. The hotter it gets the more resistance the wire has.... See where this is going? Usually the terminal in the bulkhead connector will have a melt down before the wire does.

And need to make sure the distributor is grounded good. Clamped tight and no paint at contact points on clamp or intake.

Clay

[Stripes]

I have a 10 guage wire running off the starter battery cable to a 40 amp relay. Relay trigger by the old start wire. I did this to ensure current to the HEI. 30 amp fused. Maybe the relay is getting hot and fluttering the voltage to the HEi? If so a wire direct to the pos battery post to the hri should keep it running for testing.
Fastronix 50/30 Amp Weatherproof Automotive Relay and Socket Kit https://www.amazon.com/dp/B01CXA42XK..._tDv7DbKTZJTPE

[Stripes]

Thinking about the distributor ground. The base has a gasket between the block and distributor. The clamp ears are dipped in plastic. The gear on the distributor is plastic...

[shaker455]

You can run it directly off battery for testing.
I don't wire off a relay, directly off a keyed 12-volt source that is constant while running.
Best is to put a meter on the wire where it's plugged into HEI while running to see what it's actually getting for volts in operation.

["QUICK-SILVER"]

Originally Posted by Stripes

Thinking about the distributor ground. The base has a gasket between the block and distributor. The clamp ears are dipped in plastic. The gear on the distributor is plastic...

Link to recent thread about a car blowing modules. Car went from running 'just ok' to running great.
https://forums.maxperformanceinc.com...d.php?t=835855

I've ran into the ground problem before just from having too much paint.

Got to be worth checking
Clay

[Stripes]

The car runs poorly now at idle in the garage. Wired the new hei direct to the battery. Checked the float level, full and correct. Afr has risen from the normal 12.8 at idle to 22 to 1. Convinced it isn't a fueling supply or vapor lock issue. Running a ground wire to distributor next. Battery has 12.9 volts engine off, 13.5 running.

[Stripes]

Attached ground wire to distributor clamp bolt to negative battery post.
No change in it running poorly. Rechecked floats front and rear on carb, bowls at correct level, checked timing, 16 degrees advanced hasn't changed. Disconnected and plugged power brakes and pcv valve vacume lines, no change. Afr shows 19 to 22. at idle, when it runs properly it was idling at 12.6.

[steve25]

So for some reason your motor wants to idle at a air to fuel ratio that should only be taking place at full throttle, this assumes that your system to measure such is working / reading out correctly!

19 is far to lean as even motors that where design to be great on fuel milage like the 301 would cruse at 17.

I have not read through this whole string of post, but have checked to see what the motors cranking compression is?

["QUICK-SILVER"]

Think I'd see if playing with idle mixture screws changed anything.

Depending on what happens after mixture screw adjusting....Start pulling plug wires to see if the rough running can be isolated to any given cylinder or combination of cylinders.

With the factory holley carb filters took out, it's very possible some thread tape (or trash in general) has got in a jet or sucked into the metering block.

If pulling plug wires you find weak cylinders in 1, 4, 6, 7, or in 2, 3, 5, 8, you can look at the intake to see which side of the carb is acting up.

I wouldn't trust or believe any afr reading with the engine skipping or running rough.

Clay

[Stripes]

Ran the ground wire to the cleaned distributor clamp from the battery negative terminal. Made zero difference. Added mechanical fuel gauge. It read around 7.5 lbs when the car ran good. Took it out drive it 15 miles no issue. Jumped on the throttle one time and it would barely idle after that making only 4 pounds of fuel pressure and it had a 22 to 1 afr. When it is running well it will white smoke the tires thru first into second gear and when it acts up it will only go about 15 miles an hour!

[67drake]

Scratching my head here on my end, but just a shot in the dark. You say the tank is spotless, but could you have water in the tank? And maybe try getting gas at a different station next time.

[A Goat]

Originally Posted by 1968GTO421

Is it possible he got a tank of bad gas or too much ethanol?

Any time vapor lock occures the culprit is the fuel pump.

[goatman1970]

this may sound silly, but you have the dual snorkel air cleaner on that, are the vacuum lines all hooked up and switching properly? Are the diaphragms in the snorkel flappers good? If I remember correctly, those dual snorkels operate so that heat risers off the exhaust manifolds heat the air through the intake until a thermal vacuum switch opens and ports vacuum to the flappers at which point the flappers open and you get fresh cool air. If the vacuum doesn't open the flappers, they will continue sucking hot air off the manifolds.

[Stripes]

The duel snorkel air cleaner heat rises are not connected to a thermal switch anymore and default in a closed to the heat, open to cool air position. I've run multiple tanks of gas from different locations, doubt its water in the fuel. Runs the same on 1/8 tank as it does full.

Plan A: My new theory (guess) is the iron manifold may have been cut or warped since 1972, and possible after warm up I am getting a vacuum leak occurring. That would explain the rise in afr, the sudden rough idle and low vacuum. I've got a performer rpm ready to test to see if the issues resolved with an intake swap.

Plan B: if above fails, I have a new fuel tank with an in tank electric pump and regulator I can install and place 7 lbs positive fuel pressure on the fuel line, and disconnect the robbmc pump. Routing the return lines and wiring the electric pump is a big time investment I would prefer to avoid if plan a works.

Running a mechanical fuel pressure guage now and as expected it pulses a LOT with the mechanical fuel pump. Pulsing from 4.5 to 7 psi when car runs properly. After I push the motor a little, the bad running comes and a quick underhood check now shows a hardly pulsing 4 psi on the mechanical fuel guage. The electric holley fuel guage doesnt pulse ever and reads the same whether running well or poorly. So weird, the electric fuel pressure guage seems to be a waste of money.

[Greg Reid]

Number one task is to determine for certain if it's fuel or ignition related...

I chased a similar problem some years ago...took me all summer to figure out why my truck would start cutting out but only in the evenings on my way home. I'd pull over and it would idle back up and continue until I drove it for a couple of miles and start cutting out again. 50 mile commute, one way.
After MUCH troubleshooting over several weeks, I finally jumped out of it when it cut out and very quickly popped the breather and pumped the accelator. Just bubbles and spurts. Once I got that answered I started troubleshooting the fuel systems and I mean I checked everything I could think of, dropping the tank to check the rollover valve, fabbed fuel line/exhaust shielding, replaced pump, etc.
It finally wouldn't start at all one day.

That gave me a chance to figure it out. I found that it had almost zero fuel pressure, even after I verified the mechanical pump was good and re-installed it. Pressure good except when it was in the truck...? Turns out that a Dodge uses a pushrod between the camshaft eccentric and the pump lever. If it wears down, you get a weak shot. Until that shaft wore completely out of tolerance, the problem only occurred when it was hot in the afternoon.
Electrical problems usually follow the same pattern. Starts showing up in hot weather or when the components just get hot.
I don't know if any of that helps but something to think about. Focus entirely on determining which system it is, then you have a better chance of tracking it down. You'll drive yourself nuts going from one to the other.