Technical Voltage drop at hei

hello, I have 327 sbc hei distributor, had a no start problem new battery 12 75 volts at battery 12..60. At distributor with key on when cranking voltage at distributor drops to 9.60 volts it also drops the same at ignition switch things I've done hoo,ed battery jumper cable from ground to starter body same results, hooked multi to meter pos at starter neg at battery reading was 11.30 volts at starter it seems to turn over ok high torque mini starter 2 years old have cranked alot building car is my starter pulling voltage down ?, mike

 

Check the voltage drop from the starter to the ign switch(assuming the supply comes from the starter) then across the Ign switch and then from the Ign switch to the Dist.

 

how long is your ground cable and what gauge? You want a short ground cable and heavy gauge if possible.

 

12.50 at switch key on 9.50 at swith when cranking

 

You had 11.3v at the starter while cranking correct?
Where does the feed from the switch come from, and are there any connections in between?

 

You didn't say where your battery is mounted or how long your cables are. Also I didn't see you post the voltage on the battery posts while cranking. Your battery may be on its first leg if you know what I mean. I had the same issues with 2 red top batteries. Finally got a new regular type battery and all is well.

Edit: I also went for a new starter before I got the new battery and it helped a lot but still cranked slow. Even with the new battery I'm showing up at nine and a half volts while cranking but it fires right up every time. And my battery is in the trunk as well as the fuse block.

 

I'd check volts at battery, and I'd load test battery. Maybe swap in a known good one?

 

Almost sounds like voltage after ballast or resistance wire. I'll try reading through your test points again.

 

Load test battery just off charger 13.20 cranking 11.60 at battery. 10 gauge wire off of starter post to switch, battery 5 ft from starter also checked all connections on switch and they all go down to 9.5 when ranking

 

Did you verify there is actual spark from the spark plug wires? What color is it?
At startup there will be voltage drop as the starter may pull a couple hundred amps.
Seeing the voltage drop between 9-10 volts is not uncommon, any less than this then you may want to look for high resistance loads.

 

Can you get to the + battery terminal to get a reading while cranking?
2v drop in 5' battery cable is not great but I have seen worst.
Also can you check the cable + battery post to starter post to verify the meter reads 2v while cranking and you are not losing some on the - cable too.

 

how many volts does hei distributor need to fire i pulled hot wire off of starter and I ran one from the battery to switch and gained a 1 volt but still dosen't start i now have 10.5 volts at dist cranking

 

Hei’s take full battery voltage. You don’t say the car type or whether it came with resister wire. That drop is a lot to me. Has it been starting?. is all this new? If you don’t own one those hand held battery testers are a God send so you don’t go chasing your tale..A clamp on load tester is good to have on the cable when trying to start. There were som available that just set on top of the cable in the 60’s.
What kind of starter? A 30 year old stock Delo-Remy or a China cheapie. All this matters ... more information please.

 

At 10.5 you should have spark.
Is this a HEI with the coil in the cap or a newer style?

 

Is there actually sparking?
Don't really care about voltage numbers, the secondary side of the coil will function at a lesser value but still good enough to start combustion.
Is there spark?
What color is it.

 

OK. I appreciate all of your help so far and I have checked everything you guys ask about and I have eliminated everything but the starter pulling to many amps can a bad starter switch cause this problem i ran a hot wire from battery to distributor and it fired right up

 

No you have a voltage drop from the starter to the ign switch it sounds like, it may just be a loose/dirty/corroded connection at the starter.

 

Not sure what your car is, but I remember that when I went HEI in an OT 1972 Pontiac LeMans I had years ago, I had to replace a resistor wire in the harness from the firewall to the distributor with a copper wire so it would get full 12 volts.

 

Yes, starter switch can be a problem in modified cars where the load is too great for the quality of switch.
What else is powered off the switch in addition to starter solenoid and the hei?

 

I finally pulled starter switch and found the ignition wire to the hei had a couple of accessories tap into it redid it and now have 12.5 to dist don't know why it just started acting up its been wired like that for a good while thanks again for the help,mike

 

Some cars used a resistor wire instead of a ballast resistor.

 

HEI requires a 12 gauge wire directly from a 12 volt keyed source from the fuse block


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Not to date us but HEI is getting close to 50 years old

 

I don't know why everybody changes there Dist. ( point dist) to a
HEI Dist
I have been running my 327 engine with a Dual Point Dist
for about 45 years with NO Problems.

Just my 3.5 cents

Live Learn & Dike a Fool
.

 

My 327/300 hp engine is in my 50 Mercury & I can still change the
Points every 12 Thousand miles.!
when I cant do it anymore I have a Good Mechanic I can
bring it to, he works on my late model Driver.!

Just my 3.5 cents

Live Learn & Die a Fool

 

This question was resolved in post #21.