At what RPM does a stock GM HEI drop voltage?

[DUCKY]

And what kind of effect does it have on your motor. Would retarded timing (26deg total) make it worse?

[77charger]

i think it starts at 3500.

[Jordy]

Yeah, I was thinking it really starts to drop off around 3500-4000 in most cases and gets worse from there...

[DUCKY]

So your saying that at 4500, it REALLY sucks ass
and could start to cause misfire and loading up?
[ December 18, 2002, 08:30 PM: Message edited by: DUCKY ]

[Oldsquirt]

I was always told that they started to drop coil output around 4500rpm. It is a progressive thing, resulting from decreased dwell time in the module's circuitry. There are several aftermarket modules that claim to eliminate the problem

[sdba069]

I think more like whatever speed the starter spins the motor.............Junk

[MikeF]

DUCKY:
And what kind of effect does it have on your motor. Would retarded timing (26deg total) make it worse?Retarded timing has nothing to do with dropping voltage @ higher R's.
Retarding the timing is to guard against creating total burning of fuel and O2 in the combustion chamber when the piston is near TDC, creating too much pressure there, and having it push straight into the crank, creating no turning force @ that position on the crank. eek! .
W/ the extra fuel and air (turbocharged) you are putting in the limited room of the comb chamber, the flame speed has increased, leading to a adj (later....26 instead of 35 total) to the timing to make sure the 02/fuel is completely burned when the crank is 20 deg past tdc. Get it wink .
[ December 22, 2002, 08:57 AM: Message edited by: MikeF ]

[DUCKY]

Motor's not turbo'd yet...
Will be soon.
I was just thinking that the timing being at 26deg instead of 32-34 would make the HEI situation worse.
The problem is that after a 10-12 sec hard run at WOT,(45-4600rpm) the motor did not want to idle and was chugging black smoke. It cleared out after a few minutes, and ran fine, but I figured this was the by product of the HEI crapping out.

[Bow Tie Omega]

Ducky, my brother and I had the same problem with our boats. I would leave the beach and the boat ran great. I would go out for 15 minutes and the boat would not stay started, it ran like shit. Same for my brother. My brother went to Performance Distributors and bought their HEI hop-up kit. Night and day difference. He said that when he first started the boat with the new kit, all kinds of black crap was coming out of the exhaust ( It scared him). After a few minutes of that, the boat idled great. Took it to Smellsomemore to run it, It ran perfect. 2500rpm, 3500rpm, 4500rpm, 5000rpm for about 3 hours, not one problem. He even got some extra rpm and a few mph out of it. I was so sold on the difference in his boat that I bought one for mine. Have not ran it yet, but I look forward to it. I would reccomend this product to everyone with a HEI. Here is the site and good luck...Joe. Oh yeah, make sure that you go to accessories for the hop-up kit unless you want a whole new distributor.
www.performancedistributors.com (http://www.performancedistributors.com)
[ December 19, 2002, 01:17 PM: Message edited by: Bow Tie Omega ]

[LeE ss13]

Bruce ... I second what BTO said. Modified HEIs with hiperf componets work very well. A lot of SS boats run them and we run in the 7000-8000 rpm for 5 miles at a time. I have to take note with the statement made by Performance Distruibutors that you can run .050" to .055" plug gap and that
"The wider plug gaps will allow more spark energy into the combustion chamber providing a better burn of the fuel mixture and increasing horsepower."
Actually widing the gap lessens the 'spark energy'. Like guys that run Mags have to run .015" to .020" to get the engine started because at cranking speed the spark is weak. The reason for running a wide gap is that if you have a High Energy ignitions system that has the extra energy to spare, the wide gap increases the nucleus of fuel present to better fire the mixture under adverse conditions like lean fuel mixtures mixed with exhaust (EGR) in smog legal motors. The reason someone might think the energy is raised with a bigger gap might be that on an osciloscope the firing line is higher. That only means that the voltage is higher. (the voltage goes up to jump a wider gap) The energy is a function of the voltage times the amperage and as the gap gets wider the amperage goes down. I think I'm starting to ramble. It's just that I haven't gotten to ramble like this since I taught auto shop at a local JC. ramble, ramble, ramble...

[DUCKY]

I am figuring this is the problem. Hoping I can find the module locally before the weekend. If not I will order it and steal the super coil off my Blazer.
Thanks Guys!!!

[sdba069]

I really don't know why anyone would spend money on one of those distributors,but to each his own.About the loading up problem after a hard run,that is a normal occurrence.When you slam the throttle shut after a pass it will pull a large amount of fuel into the motor through the idle circuit and sometimes a little through an intermediate passage and since the throttle plates are pretty much closed(insufficient air) you tend to load up the cylinders a little with unburned fuel.If you ever get a chance to look at EGT readings on a motor,you will see that the highest readings come after you back out of the throttle.This occurs due to raw fuel burning in the headers instead of the cylinders,fuel which was pulled in after the throttle plates were closed and wasn't burned in the cylinder.Hope this sheds some light.
Garry

[DUCKY]

Damn son, you really hate HEI's that bad? I just couldn't argue with the price (free) and if all it will take is a $35.00 ignition module to make it work well, I'm game. Now if I was building an all out race motor, you know I'd be tearing up the MSD catalog! Gotta hit the sack, 'night all.

[DUCKY]

Oh, and yes Garry, that makes sense. I have experienced that before, but this seemed really bad like I was experiencing an ignition failure, or main jets fell out or something of the like.

[396_WAYS_TO_SPIT]

So what if you run a MDS 6AL box? Wouldnt that help the voltage from being dropped? I thought the 6AL was supposed to help with more volts?????
396

[DUCKY]

I have never hooked up an HEI to a 6-box so I am unsure. If it wires in before the module, then it would work fine (I think that is the way it works), but if it uses the existing module for dwell information, it wouldn't help at all. I have since learned that it is not voltage output to the coil that is being lost, it's dwell time, resulting in incomplete saturation of the coils' primary windings, which equals a weak spark.

[396_WAYS_TO_SPIT]

Ok that would be understandable but why does everyone run a 6al box. I know it has a rev limiter but what would be the point in running it?
396

[DUCKY]

The 6A/AL boxes have several other desireable features, most importantly the multiple sparks that last for 20deg of crankshaft rotation, below 3500 rpm. MSD stands for "Multiple Spark Discharge" This results in more complete combustion, reduced plug fouling, and easier starts, according to them.

[sdba069]

Hey 396.....It bothers me that you even needed to ask that question.......

[powerplay230]

Not sure if anyone suggested this yet, but MSD sells plug in module for the HEI distributors. Have read in Hot Rod that the module raises the level at which spark falls off a few thousand rpm, think that and the MSD box would make a huge improvement. If anyone has any experience would like to hear the stories good or bad, I'm looking for improvements for a carb 502. Can't afford the little piece I really want- a procharger... :)
happy Holidays to all,
Rich

[DUCKY]

That's almost exactly what I bought. I got the "super stock" Accel unit that advertises full coil output to 6500rpm, it was about $40. Both MSD and Accel make ones that advertise "full coil saturation to 9000 rpm" but I had no need for that.
Is your 502 a Mercruiser unit? If so, the modules won't fit your distributor.

[sdba069]

Hey Powerplay........Info emailed me the other day with a blow thru Procharger for sale.I think he's out of touch for a couple of days,but you might try him.

[West Coast Dave]

When we used a HEI w/ A MSD 6A, the module in the HEI is removed and you are just using the HEI as a pick up point, similiar in concept to a crank trigger. The HEI triggers the event and the MSD box does everything else. We ran this combo with no module whatever for 3-4 years on a SBC that turns 7500 all night. Simple and reliable.

[powerplay230]

Ducky,
Yes motor is mercruiser and has the "thunderbolt" ignition on it now. I also have a almost new HEI that has Accel super coil and intensifier kit but didn't think their kit replaced the module in distributor. On a motor that isn't going to turn more than 5500 rpm what would be the best ignition for the buck, the thunderbolt, Hei, fixed up Hei, don't think Santa is going to leave a whole MSD set under the tree for me.. jawdrop

[DUCKY]

Powerplay,
If your motor has the thunderbolt on it now, leave it alone. The thunderbolt system is very good, and is better than even a modified HEI. You might add an MSD box for the purposes mentioned earlier and possibly a low impedence coil, but thats about it. Unless "santa" leaves that whole MSD setup for you...
[ December 23, 2002, 07:17 PM: Message edited by: DUCKY ]

[DUCKY]

West Coast Dave:
When we used a HEI w/ A MSD 6A, the module in the HEI is removed and you are just using the HEI as a pick up point, similiar in concept to a crank trigger. The HEI triggers the event and the MSD box does everything else. We ran this combo with no module whatever for 3-4 years on a SBC that turns 7500 all night. Simple and reliable. That's the way I thought it worked, and being so, that would be fine.

[396_WAYS_TO_SPIT]

sdba069:
Hey 396.....It bothers me that you even needed to ask that question....... Gary..... It bothers me to wanna learn....... :D :D
396

[sdba069]

Hey 396,I understand.Hey Ducky,looks like I'll be delivering a Mirage Outboard out to Havasu City about Friday.

[DUCKY]

Sorry Garry, I didn't see the post. I wish I could afford to have you bring that Mirage jet with you too :D :D Next ime your in town give me a call.

[DUCKY]

396_WAYS_TO_SPIT:
sdba069:
Hey 396.....It bothers me that you even needed to ask that question....... Gary..... It bothers me to wanna learn....... :D :D
396 We all gotta start somewhere! I was blessed (I think...) with being immersed in this stuff from an early age.

[sdba069]

Hey Ducky......I ended up having it transported out there,it got there today.But it didn't make the trip unscathed,apparently the driver jack knifed the trailer and mangled the left sponson.But the guy took it anyway,I just have to pay for the repairs.Maybe you'll hit the lotto and you can buy the red one and the white one.Later and Happy New Year...........
By the way,if I can help you with the motor problem,give me a call...254-889-3336
Garry

[Bow Tie Omega]

SDBA069, people mess with those distributors because they do not want to spend $700 + dollars on an Msd Ignition for a boat that they use 2-4 times a month in the summer. A little wake up call, not everyone races their boat. Let me see, $125 or $700 +. To each their own.

[DUCKY]

sdba069:
Hey Ducky......I ended up having it transported out there,it got there today.But it didn't make the trip unscathed,apparently the driver jack knifed the trailer and mangled the left sponson.But the guy took it anyway,I just have to pay for the repairs.Maybe you'll hit the lotto and you can buy the red one and the white one.Later and Happy New Year...........
By the way,if I can help you with the motor problem,give me a call...254-889-3336
Garry Hey Garry, I know a good 'glass shop here in town, if the guy needs one.