At a loss - engine stalls under load

[Kelley W King]

To me it sounds like you have a vacuum leak. Hard to hear with a BB at 1,000 RPM. I think you might have caused it during your carb change. Does the different carb have a port not used?

[R68GTO]

primaries are bone dry at idle.  With old carb that Eric worked on, I had 14.5" vacuum.  New carb is 5 inches of vacuum.  I haven't reached out to Eric yet but probably will once I get done with Camaro Nationals and Supercar reunion.
KK, I'll double-check on the unused port thing in the morning.

[R68GTO]

Update....I sent the carb to Eric who found a few minor issues plus found the rear float was set near the bottom of the bowl.  He said that would definitely cause my stalling at heavy throttle.  At one point I had checked the float level in both bowls and set them to the bottom of the sight screw hole but obviously jacked something up.  I won't have the carb back in time for the SuperCar reunion but think I have it running good enough to do a few smoky burnouts and take a couple of easy passes with it.  It's been roughly 50 years since this car made its debut on the strip as Rat's Nest

[WaltZ]

Just throwing this out there.
After the floats checked, try increasing the squirter size +2 and test for any difference in stumble,
if it's better, then try the next accelerator cam up, try again and if the stumble is lessening, try the next couple of cams.
Had this stumbling and sometimes stalling issue with my stock 302 and when bumping up the accelerator cam, it took care of the stumble and stalling, therefore it was starving for fuel during load and acceleration by the pump cam curve not being enough.
It may be a good idea read and understand how these cams can affect your performance, for better or for worse.
Been thru it and I know your frustrations. Sometimes it just the simple checks we overlook.
Good Luck

[R68GTO]

Got the carb re-installed and it is 100% better so I guess I can confirm that I "jacked it up" somewhere along the line.

[David K]

Glad it’s fixed. Refer to post #13 for the possible issue cause.

[R68GTO]

One more update....periodic stalling problem under moderate to heavy load continued.  Took it to a chassis dyno so we could troubleshoot under load.  Dyno guy has been tuning engines and using a dyno for over 20 years - after 3 hours he's scratching his head.  Because the stalling was so immediate (like turning the key off), he decided to temporarily install an MSD distributor and MSD box to effectively bypassed my entire ignition system.  Viola!  problem disappeared.  Made another jet adjustment and some other tweaks and the car has "woken up" pulling well to 5,500 rpm.
So the problem is on the inbound side of my coil.  Ultimately found a melted wire that goes to the positive side of the coil.  I'm not sure I understand why that condition caused the symptoms to be what they were as a melted wire is melted at both low and heavy throttle.  What I do know is when we took it out of the circuit, the problem went with it!

[David K]

Awesome. Where was the coil wire melted? Near a heat source?

[R68GTO]

It was melted from the coil back into the taped bundle of wires that runs along the firewall.  I haven't opened the tape up to see how far back it's bad

[David K]

Do we get pictures?

[R68GTO]

Here's a couple of pics....melted at the coil and at the firewall box, so assume it's melted in between as well.  I'm bummed that my original harness is toast.  New harness has differences despite claims of being factory correct.  Oh well, some parts don't last forever and on the bright side I didn't start my car on fire!

[David K]

Well that’s not pretty, BUT, you might be able to unpin the wire from the block and replace it. There’s enough used harness parts so finding an original is easy.

[169INDY]

My Electrical Apprentice Instructor reminded us.
P=I2R
Power Equals Amps Squared times Resistance.

We all know the function of that wire is to voltage drop (IR) by way of resistance some of the available voltage to the primary winding and the points to preserve point life.
The cost is Heat that is dissipated by the length of resistance wire.

I have not found a vendor source that is selling raw lengths of GM applicable resistance wire & the Harness vendors plainly state they do not sell "Parts" i.e. various connectors, terminals and wire. So Harvesting a Donor harness to obtain a used acceptable chunk of wire to repair your existing harness might be in order.

This is Where I obtain terminals, connectors and tooling for Harness repairs.

http://www.texasindustrialelectric.com/_packard_terminals.asp

[R68GTO]

My frustration has peaked.....installed a new harness to replace the melted coil wire and the symptoms still exist.  I need someone with a logical mind to help me out.  The symptoms disappeared on the dyno once we swapped out to an MSD distributor and box..  Found the melted wire as stated in the above posts so assumed that was the culprit - apparently not.
Does this mean my root cause issue is "upstream of the firewall connection?

[maroman]

I THINK you need to find out why the wire melted.