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  #16 (permalink)  
Old 07-10-2019, 06:10 PM
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Quote:
Originally Posted by BogiesAnnex1 View Post
The block ground is for the starter and mild electrical fields that are DC in nature, even the heads are pretty safe with this bonding to the block with sealant laden bolts and gaskets. The 6AL in not so kind, it is shocking the plugs with a high energy square wave pulse that is hard to absorb through these unintentional connections. Running the heads and intake together with some number 10 wire to the frame or battery negative post insures the ground side of the plugs doesn't find a sneak circuit back through the electronics. This recommendation is nothing new it usually can be found in MSD's instructions but not always it seems to come and go on reprints.

I would love to see some directions from msd that mention separate grounds and grounds from the head to the intake. And where in the world do you get the idea that "a high energy square wave pulse that is hard to absorb through these unintentional connections."? I've seen you write it many times and just wonder what your electronics background is? Have you watched the square wave signal on a scope? Have you EVER worked on equipment using a scope to check a square wave pulse? Has anyone here ever benefited from running extra grounds like you always suggest? Not that I've seen. Can you please show me one set of instructions warning you of "sneaky" electrical pulses?

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Old 07-10-2019, 11:18 PM
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I had problems with my MSD, one box failed, then the new one would miss at higher rpm, tech said to ground the heads, grounded heads miss went away and box has lasted years without a hic up.

https://forums.holley.com/showthread...Ground-diagram

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We have discovered for decades now that the motor-plates and the ground strap to the block does not provide a sufficient ground. It was initially un-covered that the black etch marks that appear around the block holes of front and rear motor plates was made due to the poor ground paths(we even saw etches in main and rod bearings). With coated studs, aluminum heads, coated gaskets,powder coated frames and customers relaying on the ground strap from the chassis to the block was not enough.
To be frank, the spark plugs are in the head and not the block! With this in mind, it was best to have a common ground between the electronics, battery and even the coil to eliminate any floating ground issues that may occur. Majority of the time ,this elinminate "misses" ,tach issues,data logger problems..etc.
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Old 07-11-2019, 06:06 AM
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A poor ground as they say is hard to believe but I suppose possible when people are trying to get a good ground through powder coated paint. With a low ohms high frequency meter I measured from one header bolt through the head, through the block and manifold, through the other head and to the header bolt and found I have somewhere around .01 ohms or less resistance as my low ohms meter was at it's low limit. The higher the voltage the less it is affected by resistance, and we know the spark pulse is high voltage. I'll have to check the frequency of my low ohms meter, but I believe it goes higher than most engine rpms.

It's just funny that my msd 6al box instructions only say to run the ground wire directly to the battery negative cable. Nothing mentioning the heads. Think of all the phone calls alone they could avoid if that were in the instructions.
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Old 07-11-2019, 06:53 AM
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A poor ground as they say is hard to believe but I suppose possible when people are trying to get a good ground through powder coated paint. With a low ohms high frequency meter I measured from one header bolt through the head, through the block and manifold, through the other head and to the header bolt and found I have somewhere around .01 ohms or less resistance as my low ohms meter was at it's low limit. The higher the voltage the less it is affected by resistance, and we know the spark pulse is high voltage. I'll have to check the frequency of my low ohms meter, but I believe it goes higher than most engine rpms.

It's just funny that my msd 6al box instructions only say to run the ground wire directly to the battery negative cable. Nothing mentioning the heads. Think of all the phone calls alone they could avoid if that were in the instructions.
True. I went by the instructions which say ground the box to the battery, now I see something different online that shows to ground from chassis to one head, then to the other head and the coil ground meeting there, from there ground to block and then the masd block ground would join this wire that is grounded to the other side of the frame and then the battery, in tendem.

definitely was not in instruction. I will wire it that way and see.

Was also thinking. if I am only at 8 degree initial timing and my plugs at .40 would not tightening the gap on the plugs help me get closer to 10-12 degrees initial?

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Old 07-11-2019, 07:26 AM
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True. I went by the instructions which say ground the box to the battery, now I see something different online that shows to ground from chassis to one head, then to the other head and the coil ground meeting there, from there ground to block and then the masd block ground would join this wire that is grounded to the other side of the frame and then the battery, in tendem.

definitely was not in instruction. I will wire it that way and see.

Was also thinking. if I am only at 8 degree initial timing and my plugs at .40 would not tightening the gap on the plugs help me get closer to 10-12 degrees initial?

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No on the gap/advance. Electricity/current is much too fast to ever play a role in a cars engine. If your msd box is working there is no need to close the gap on the plugs.


How exactly does the engine "stumble"? Does it get up to the rpm and just quit going faster? I've dealt with many problems with fuel turning to vapor and the pump not being able to keep up. When it stumbles, try pumping the throttle and let me know if it gives it surges of power (from the accelerator pump). That would point to a fuel problem. You say you have a points distributor, if it's very old, the distributor could be the problem.
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Old 07-11-2019, 07:32 AM
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I know it's hard to believe, but grounds make a huge difference.

Grounding the intake made my gauges settle down and read accurately, but the biggest surprise was my alternator. The 140amp alternator struggled to keep up with my cooling fans (50amps), I added a large dedicated ground and instantly no more problems. I can only image the long term damage the alternator could have caused to my motor absorbing all that current. It's eye opening, especially when you consider grounds are easy and cheap insurance.

JMHO, and I'm a little anal about ground paths, I don't like to daisy chaining grounds, I star ground everything.
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Old 07-11-2019, 10:12 AM
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Originally Posted by 55 Tony View Post
I would love to see some directions from msd that mention separate grounds and grounds from the head to the intake. And where in the world do you get the idea that "a high energy square wave pulse that is hard to absorb through these unintentional connections."? I've seen you write it many times and just wonder what your electronics background is? Have you watched the square wave signal on a scope? Have you EVER worked on equipment using a scope to check a square wave pulse? Has anyone here ever benefited from running extra grounds like you always suggest? Not that I've seen. Can you please show me one set of instructions warning you of "sneaky" electrical pulses?

At my age I probably have more Tektronics time than most people have lifetime, somehow high energy fields and how to dissipate them became an engineering specialty in my career. "Sneak Circuits" is a term used in electrical engineering to describe unintended current flows in places you don't want them. By the time a product is delivered to the end user these things should be worked out, but sometimes you get surprises either because you as the engineer missed some combination of possibilities or as often happens your best efforts efforts at "idiot proofing" fall short of what installers can and will do to it.



This is not something you would see on a scope unless the ground side is inadequate. From a consultant side to automotive projects and from a part to full time builder, depending on time periods in my life, I've seen several 6AL failures that appear to be ground side issues especially with the SBC Gen I. Although, I encountered a Ford small block powered kit car built by a guy in Arizona that repeatedly ate its 6AL that after adding top end grounds had no more problems. Of course since your replacing the dysfunctional box with a new one while adding grounds you don't know for sure whether you've gone through a multiple series of bad boxes and now have a good one or whether the added protection of the top end grounds are protecting the electronics from feedback.


Since I don't like comebacks no being stopped in the middle of nowhere myself; I "scrub" grounds thoroughly and add a top end ground circuit for these boxes. Compared to failure hunting, R&R time; stripping a couple three lengths of wire adding terminal ends and tucking it together is a better use of my time than responding to panic phone calls, hunting intermittent failures that don't in the shop, dealing with upset customers or being stuck myself.



Understanding what poorly bonded equipment ground side failures look like and if you read MSD's installation instructions they make a point of telling the installer to be sure the block is well grounded. Seems to me I remember some years back they recommended adding top end grounds either in their instructions at the time or it was while talking with their tech helpline people. Then adding my knowledge of electrical bonding and energy dissipation with the understanding that paint, corrosion, lubricants and sealants are poor conductors if at all it makes sense to insure that the top end is electrically tight. Given the typical engine ground strap is some distance away from the heads and generally not thought about in terms of condition or maintenance for projects that I turn out for people I started adding grounds to the heads and intake using specific bolts that typically don't end with an open passage that needs to be sealed against coolant or oil. I use an electrically conductive grease on the threads to try and stop corrosion and keep water out, but that is an uphill battle if don't live in the desert southwest.


The typical failure mode of these things is inexplicable and intermittent miss fires, inability to get power out of the engine but it idles fine sometimes even runs in the medium rev range. As time goes on this worsens till the engine just either stops running or won't start. sounds a lot like the OP's issue. Might not be, but does lead into a path I and others that have written about on this forum with some frequency. Given I'm not standing there, I can only give general advice as I have no idea of what the installation looks like in configuration or build quality. Based on my experience with automotive, boats, and aerospace many if not most installations and repairs are hacks at best and I'm not excluding myself.



Obviously if the box is failing there are no external fixes that will bring it back. If you read what I wrote carefully you will see I included contingent statements on grounds to the effect that its an "if" proposition that if good grounding is not present the failure being seen can be the box going out from unintended current flows seeking a ground path. At this point which I may not have made clear if the box is dying it's gone and will need replacement. Adding ground networks is a CYA going forward on a just in-case basis.


In the bigger picture I rather think that these multi-spark, high energy ignition boxes are far from necessary if this isn't a race car expected to earn its keep. Solid state ignitions were first designed to eliminate point contact wear which along with lead fouled spark plugs was a frequent maintenance item back in the good old days. Really except for this these issues the inductive ignitions worked fine even with the quite high compression ratios popular back in the late 50's through 60's, and they did on using 6 to 9 volts on the coil. HEI ignitions came about in the early emissions era to stabilize engine running quality over a longer time period than the typical points tune up to cover those people who didn't get a tune up till it just about stopped running. This was cause of significant pollution. The other factor was lower compression ratios to reduce NOx emissions teamed with leaner mixtures to reduce HC emissions were harder to ignite a failure here resulting in high emissions of HC's, so a harder jolt to the plugs and longer duration spark was employed to insure the burn not only started but was on time every time. Now of course this allows plugs to run wider gaps which again covers pollution from those that don't monitor such things. Today we have coil on plug which allows the individual coils more time to saturate between triggering than one coil supporting multiple cylinders. This eliminates a host of losses in the distributor and lengthy plug wiring. Some aircraft engines tried this trick in WW II using mechanical switching, but that proved too complex. Solid state switching being a much simpler solution. Multi-strike and capacitive discharge ignitions ignition came out in a similar time frame to HEI but except in rare cases the OEM's did not go that far. After 40 years of looking at and playing with these things I'm not convinced that for the average street rodder they bring anything useful to the table.



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  #23 (permalink)  
Old 07-11-2019, 11:36 AM
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Well Bogie, your knowledge and experience blows mine away. I have never been on the engineering side of electronics. I sincerely hope you will accept my apology for questioning your expertise in such a rude manner.

I do have a question that popped up and makes me really wonder. When you say the 6AL boxes can get worse over time, what type of components is it that is going bad?
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Old 07-12-2019, 05:48 AM
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Ok so I grounded they heads to the block then to the frame on both side. Then I cranked it up and got the timing light out again. The dizzy is moving when I increase rpms. I can literally see it going from 10 to 0 as I increase rpms. I know I know...lock it down. The dist lock sux. Itís a chrome one and the metal is soft. Iíve bent the teeth on it once as it flattened out. The lock down bolt is not bottoming out. Any suggestions on helping the dizzy lock down?

Just seems like a cheap lock down...

Will take it out this weekend after fixing this and update.
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Old 07-12-2019, 05:50 AM
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Dig out your old steel lock down and use that.
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Old 07-12-2019, 06:25 AM
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Dig out your old steel lock down and use that.
don't have one. stopped by napa on the way in, and the one they have is the same i have. cheap made in china chrome crap. I know thats not hardened steel cause when I bent it the 1st time i felt real iffy, thinking is this thing gonna crack.

Ill call a couple other suppliers, but probably headed to the junk yard tomorrow.
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Old 07-12-2019, 06:27 AM
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This may sound really dumb but you don't have it on upside down do you?
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Old 07-12-2019, 06:35 AM
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This may sound really dumb but you don't have it on upside down do you?
LOL, should I be insulted.....
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Old 07-12-2019, 08:00 AM
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It wasn't meant to be. I just think of the two I have and I've heard before that they are weak, but mine are hard as hell. Without lookiing I'd guess 1/4" steel.
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Old 07-12-2019, 08:02 AM
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Hard to beat a factory clamp, they just aren't very attractive if you are into all that fancy blingy looking stuff. Chrome sucks because it is slippery.
https://www.summitracing.com/parts/n...make/chevrolet

Check to make sure the distributor isn't bottoming out on the oil pump drive before it fully seats on the intake manifold, I usually check it without a gasket, if it seats fully without the gasket it will have enough clearance when the gasket is there. If it is held off the manifold seat, no clamp in the world will hold it because it isn't pressed down against a surface, it is pressed against a rotating pump drive.
You can end up with one that doesn't seat due to head and block machining, or incorrectly cut manifold.
Sometimes just a doubled up gasket is enough to fix a problem.

Just something to check and verify.
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