1) Is a drop from 12V to 10V at the batt terminal of an HEI enough to prevent the dist from firing the car from starting?
2) Is a voltage drop from 12V to 10V when the starter is cranking "normal"?
Thanks
Shane

 

Shane,

The drop from 12v to 10v is normal for a points system. You see the drop because the current is passing through the resistance wire.

I'm not 100% sure but I think it should still fire and run with 10v. But you don't need or want this voltage drop for HEI. You should run a new wire from fuse panel to distributor.

Make sure the distributor is getting a good ground through the hold down bolt/clamp.

For a simple test I would run a jumper wire from the altenator to the distributor to give a full 12v and see if it will run.

I had a similar issue with my 71 with points/condensor setup. I had 2 problems; too much voltage drop through resistance wire while running (about 9 volts), bad coil. My Accel coil tested normal (ohms readings) but when I replaced it the car started up and ran great.

Are you getting any fire at the plugs while spinning the engine over?

Roger

 

Already ran a new 12awg wire from the IGN terminal on the fuse panel and am seeing a drop to 10V when cranking there as well. I also checked voltage levels at the alt terminal while cranking aand that drops to 12V as well.

Really, really weird issue.

 

I'm at work. I will be home in about 1 hr and will check voltage on my 71 while its spinning over trying to crank, and after its running, and let you know. I'm pretty sure I have 12v at coil while its spinning over because there is a wire from the starter to the coil that feeds 12v while cranking.

Did you check to see if any of the spark plugs are firing? When my Accel coil was bad, my plugs were firing but not hot enough to run.

Are you certain when putting the distributor in that you got the rotor lined up correctly with #1 plug wire? I put mine in 180 degrees out one time. If yours is out 180 you will get backfiring through carb or exhuast depending on distributor location.

Roger

 

Are you getting a voltage drop due to the distributor current draw, or due to the battery voltage dropping? Big difference.

A real HEI is designed to work down to 5-6 volts. Aftermarket copies rarely perform as well at low (or high) battery voltages or ambient temperatures.

 

100% sure the dist is in right. double checked, reset to TDC om compression, etc etc etc

 

Rreal HEI....MSD 8365

 

Prob a dumb question.....But how do you see if your plugs are firing?
I have also tried several coils which I am highly sure are good with no luck

 

Have you spun engine with one sparkplug out of engine but grounded and connected to plug wire to see if you are getting any spark at all?

Roger

 

It's a good question. Connect a sparkplug to one of your plug wires and lay it on the exhaust manifold or other steel that is grounded. Spin engine over and watch for sparks jumping across electrode. It should make a blue spark. Don't hold it in your hand it will shock you. There is also a little tool you can buy that cradles the spark plug wire and shows spark, but I haven't seen one of those in years.

Roger

 

I saw on another post someone recommended a test light between the tach terminal and ground. Did you do that test? If so, what did you find out?

Roger

 

Pulled the plug, connected the wire and grounded and there was a small spark which looked more orange than anything.

I also placed the 12V test light from the tach on the dist and grounded and it did light up.

 

Well, it sounds like a visual copy of an HEI. It's not a real HEI.

Nevertheless, it should be designed to work just fine at 10 volts. It's the ability (or lack thereof) to work/survive the voltage ripples and transients that are always present in wiring harnesses that are a trademark of many aftermarket systems.

 

Shane,

Here's the voltages I measured:

71 Vette with stock points/condensor/distributor - Measured 10.2 volts while cranking.

76 Vette with stock AC Delco HEI - Measured 9.8 volts while cranking.

The test light shows that your HEI ignition module is firing.

You have tried more than 1 coil so I think you can rule that out.

Orange color of spark seems weak but if it wasn't grounded very good it would show up weak. You could have a bad rotor or center connector in the dist cap causing a weak spark.

When you rotate the distributor either way, do you get any backfiring through the exhaust or carb?

Roger

 

No backfire, spitting or anything....Like it is not firing at all.
So what would cause such a weak spark? I can put the new dist back in and see if that changes things but I doubt it (the old carquest unit is in now).

I also verified I have a good ground connectivity from the neg onthe battery to everything in the engine including the distributor.

I did measure the resistance from the IGN wires I have going to the dist and it measured at .023. Seems pretty low. Possible short somewhere?

 

Weak spark can be caused by bad rotor and/or dist cap, bad spark plug wires (doubtful they all went out at one time), or bad coil (you tried several so this is most likely not your problem).

You have tried 2 distributors (checked with test light) and multiple coils so I don't think those are your problems.

When the engine last ran, did you turn it off, or did it stop running by itself?

Roger

 

I turned it off.

 

Shane,

Does the inside of the dist cap look okay? Check it with a light and look for hair line cracks or a missing tip in the center that connects to the rotor. Make sure its doesn't have any moisture in it. Even if the cap was cracked it should misfire, backfire, etc, unless it's missing the center contact to the rotor.

Check the rotor to make sure its not cracked or burnt, melted, etc.

Do you have another vehicle you can use the coil, rotor, and cap from to check them.

If you find the rotor and dist cap okay, then you could have a couple of other things to check:

Prior to checking the more serious things below, have you tried using starting fluid? I know it's not the best thing for an engine but one or 2 shots won't hurt and might get it running so you can check/set timing, carb, etc.

1. Check timing between cam and crank - remove drivers side valve cover and turn engine over make sure #1 cylinder intake valve opens just before compression stroke then closes and exhaust valve opens during exhaust stroke. I once had a mustang that jumped timing one tooth. Behaved sorta like yours is doing. Mine would backfire occassiaonlly.

2. While you have valve cover off verify again you have the dist rotor pointing to the #1 plug wire on the compression stroke (voice of experinece speaking here).

3. Make sure valves are adjusted correctly and didn't work their selves out of adjusment while you were driving it. I once had a freshly rebuilt engine have this issue. I had to replace the locknuts on all of the rocker arms. The old ones were too worn out and would loosen up while running until the engine wouldn't run anymore. You might have just shut your engine down before it was ready to shut itself down.

Roger

 

Tried both the old carquest dist and the brand new MSD 8365. The carquest looks good all the way around as does the MSD.

I could try starting fluid but I feel like fuel is a non-issue. My electric fuel pump is working fine, my gauge is showing the same pressure.

I degreed the cam per the specs and used a new double chain timing set.

I could check the lifters, etc but everything is brand new and locked down. I will check again though. I will also verify TDC.