I'm putting together a test stand to break in the cam on my engine. I'd rather not remove the alternator & related hardware off of my 85 to put on the test stand, so I'm wondering if a good charged up battery would be good for about 1/2 hr of use? It will be running an electric water pump along with the hei.
I do have a 10/50 amp battery charger that I could leave running on it during the cam break-in which may help.......

Thoughts?

 

Should be
Have run in plenty of flat tappet engines only using a battery

 

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Use the battery charger, it will be fine.

 

 

what are you going to do about cooling?

 

He mentions that he uses an electric water pump.

 

Thanks for the replies. The electric water pump is what I'm concerned about how much it will draw off the battery. If it gets too low to pump or spark, I'll just have to shut it down & recharge the battery. Hope to fire it up by the weekend.

 

As mentioned, use the battery charger while the engine is running. It'll act as an alternator.

 

Nope....
not for long !

maybe a few minutes...that's all.

HEI has a HUGE drain on the battery. A fully charged battery has enough amperage to charge the HEI for about 5 to 10 minutes....the higher the rpm the shorter the life of the battery. HEI trades away volts for amps...and the spark gets slower as the amperage goes lower. Higher the RPM the lower the voltage essentially. What WAS a 40,000V spark at fast idle is reduced to 15,000v at 3000 rpm. The faster you go the weaker the spark because it takes more amperage to push it faster.

Hope this is making sense...I may not communicate this well, but I think you'll get the gist of it...

It takes about 11.8 v to charge the HEI capacitors and generate spark for normal speeds. As rpm increase voltage decreases...and you can watch the volt meter drop by 1/10ths until it starts to misfire at around 10.8v at 2500rpm...or 3000 rpm and 10.5v. As voltage drops so does the rpm...the HEI does not have the voltage necessary to keep up with the high rpm load. That's why/how it uses battery so quickly.

HEI is a trade...volts to amps. This "swap" sucks the voltage right out of a DC source. As the voltage drops the HEI charge rate from RPM increases so the drain starts to get pretty fast. If you slow down to a low rpm it will last longer. .but not much. Less rpm equals higher voltage spark, so the battery gets sucked down anyway,.. its a "no win" situation.

So, if you lose the alt going down the freeway at 2000 rpm, approx. 65-70 mph you have about 10 minutes at that speed before it starts to misfire...then you drop to 55 mph where there is still enough voltage at that speed...until it misfires and you slow down even more. Soon (15 min total) you're only able to get 20 to 30 mph and your Volt meter is showing <10V....and at about 9V it starts to sputter and will die. The HEI cannot generate ANY spark with less than 9V...maybe even 9.8....I forget. Its been a while.

The battery charger might prolong this BUT its going to be like cranking the starter with the charger set to "charge" and that's hard on chargers...it shoots voltage or amperage thru the system in ways its not supposed to. High load/resistance I guess. Having the battery charger ON is NOT the same as having an alternator charging. Alternators provide 100+ amps where the battery charger is giving up less than 10? maybe? that's a strain on the system and why they recommend that you do not crank the starter with the charger set to 'charge'.
As we know, with electricity, a strain or RESISTANCE = HEAT...things melt/burn.

So, ya got about 15 minutes to do your thing. Then, its time to either recharge the battery OR swap in a fresh battery... cause HEI eats 'em alive.

 

The ignition system will draw a lot of power also. That's the reason the ignition module gets so hot. It's pumping a lot of current through the ignition coil.

I blew my alternator while autocrossing at Firebird Raceway in Chandler, AZ. I drove the car back to my hotel in Tempe, AZ, mostly on I-10. It took maybe 15 - 20 minutes to drive that far. After changing alternators I still had plenty of battery power to crank the engine and start the car.

You should be able to run the engine long enough to break in the cam.

 

Ok, Thanks, I'll give it a try. I just thought of something....I could also take the bat. from my daily driver and hook the two up parallel with a pair of jumper cables. Of course then I'd have 2 dead batteries.

I hoped to be able to break in the cam this weekend, but some family issues arose last night that may set me back a couple days. I'll post a video after I get it running.

Thanks again,

Carl

 

its very difficult to predict, I admit. It depends on the battery condition, the HEI condition and everything else. I know MY experience has been that of a very limited run time after the alt dies... the instant you figer out the alt is gone, you turn off all non essential items, and hope the fan is not running your battery to death...

I wonder if deep cycle batteries would do such a thing for a longer time? or the red-top whatcha callits? the expensive battery that has the cyl like cells? Traded mine away when it kept going flat.....

anyway, when you do this, take note of the rpm and where the voltage is when it starts to misfire. Its good info to have for future reference.
Just keep in mind....the faster you go the lower the voltage gets because it is forced to go faster to keep up thus drain happens quicker...the slower you go the higher the voltage BUT the lower the amps draw so the batt last longer..
have fun !

 

One of the batteries I'll be using is one I pulled out of my pop-up camper which supposedly is a "deep-cycle", but it's only 550cca. I just bought a new battery for my Mother's 2002 Cad. Eldorado so we could sell it, but it has tranny problems, so I'll pull that one out and hook that one up parallel. I will add on my multimeter to monitor the voltage and post the voltage when it starts to misfire.

This is all depending on if I built it right and it runs that long w/o other problems....... Will be nice to hear it fire up though.

 

Sorry, but that is 100%, dead wrong. You can run an HEI ignition for HOURS, on a decent battery.

WITH E-water pump? Probably at least an hour.

 

I shorted my alternator with a wrench one time and it killed it. I didn't know it at the time. Just went about my business. Several days later, after driving my car, the dash started going crazy. I noticed my voltage and shut off my headlights and the car started to act normal again. Shut everything off and still drove it home. It will last a long time if the battery is good. I didn't have an electric WP but still, mine lasted many hours of driving.