That's right, Pins ERB have their own wires that bypass the relay box and go directly to the MS.

What can I swap in place of the HEI module? Another one?

And for the record, it runs better with the tighter gap, and idles about 2 RPM higher now, but it still falls on its face above 100 KPA. I can take it up to around 3K RPM in 3rd as long as I hold it below 90 KPA or so, but then it begins to fail. Were it runs, it runs very well. And is returning good mileage.

Sam

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I think you have something there.

Have the HEI and MS grounded at the same spot together so there won't be any voltage grounding differentials giving you a spurious signal.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I am pretty sure they are grounded at the same spot. Just out of curiosity, should the case of the MS box be grounded as well? There is no external ground as such. Any groiunding takes place through the relay box and cable. The MS box is screwed to a piece of aluminum which is screwed to the underside of the dash. Should I be running a ground wire from the case to the firewall ground block.

I have several ideas for improving the grounding of all the sensors. There is currently a ground block on the firewall which is grounded through a wire which is doubled up through a lug bolted under the old ground strap to the head. I am thinking I should take a number 12 wire directly from that block to the head to eliminate one connection in there.

IN spite of adjusting the air gap and putting shielded wire on the VR signal wires, it still stumbles and loses power when pushed into the boost range, or you try to push it above 3500 in 2nd gear. I must say, the drivability of it is excellent, other than this. The idle RPM went up by 200.

I just have not had time to spend on it this week, so will get back to fuel tuning next week, and see how much of an improvement it generates.


George, what do you gap your plugs at. Peter had me gap mine at .25, which is what his BMW runs at on essentially the same plug. Others I have talked to think this is too tight. What are your thoughts? WE did this initially based on the theory that the flame was being blown out by the turbo.

Sam

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No, there is no need to ground the MS case. I don't think anything is grounded through it. My box is mounted to the plastic of the heater suitcase with no grounding at all.

I gap the plugs at .035 right now. I will probably go to a smaller gap like yours when I'm boosted

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Drove it yesterday, and still failing predictably in same places.. Guys stood around at the cruise with suggestions for fixing the problem, which was interesting. Most knew nothing of EFI, but had interesting perspectives. There were five Mopars there, including Kevin (64conv65hard) from our forum, and we ended up shutting down the place, hanging out talking.

Here is list of actions taken recently:


1. Installed Shielded cable for VR pickup.
2. Closed reluctor gap down to .008 spec.
3. Made sure all grounds were clean, and referenced to same local point on head.


It still reads wrong RPM as evidenced by short data log I made. It is only a short idle and rev event but there is RPM of 5000 recorded which I know did not happen. I never revved it over 3K. So, it is picking up spurious inputs from somewhere. Any ideas about what to try next? Possible culprits:

1. Distributor?
2. HEI module?
3. Spark plug wire leakage?
I think fuel contributes to the problem, but simply reveals it, not direct cause. The VR signal wires are not shielded for the short distance from the distributor to the shielded cable. This is maybe 5 or 6 inches. Could a faulty pick-up cause this type of failure? I can see it dropping events, but not adding them.


After making changes 1-3, idle RPM went up by 200. Starting and drivability are superb. I could not be happier with that. And mileage is good for what it is and how I drive it (short trips). But it falls flat on its face when pushed. Why would it always fail under the same conditions, if it is RPM related, which I think it is? It is nice to know it is consistent. This leads one to the hope that when the culprit is found, that will be THE fix. Although I am sure fuel needs lots of work as well. Random events are far more frustrating, and discouraging.

Ed, the relay box, which carries the ground from the MS computer and the HEI are grounded to the same spot on the head with #12 wire. The connectors are crimped on for the HEI module, and soldered for the box. Should I solder them both. I hear mixed opinions about this.

I wish I knew more about the three different types of filters. This might improve my diagnostics.

As Always, Thanks Sam

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It's actually encouraging to me that you can consistently reproduce the problem because when it is fixed there will be no doubt. Much better than a intermittent problem.

Culprits:

1. Maybe.
2. More likely.
3. Should be able to move the problem around by moving the wires, and that's not happening.

If I were not seeing the RPM spikes in the datalog, I would suspect we are on the threshold of crossing between an ignition configuration problem, and just needing to tune. I ran into that when I went to ignition control on mine. I'd scratch my head wondering if I needed to change a fuel input, or something about the spark.

You are not there yet, because we have these doggone RPM spikes to eliminate. Once that is done, we'll be on the home stretch. The thing we need to figure is, is it breaking up due to RPM, or boost? Because you get one with the other. My hunch is RPM.

Now, did you turn the noise filter *On* in the tuning software yet? It was off in the .msq you sent me. I'd be very curious to see how that affects things.

Click on 'Basic setup'
Go down to 'Noise Filtering' and click
Under 'Primary Tach' (in red) the first entry is 'Noise filter enabled' and it's currently off
Select it 'On" in the drop down.
Select 'Burn'

Try it

Interesting thing is if that works, it's curing the symptom, not the problem. Still, working is working and I'd be hard pressed to mess with it any more if it were me

On the grounds to the head: How is the engine itself grounded? I'm assuming there's a rather large cable from the block to the chassis/battery.

BTW, as an aside, when I was racing my Nova with a HEI, common wisdom was that it was only good to about 4000 RPM stock. I used an MSD HEI module because I was running 7200 RPM...

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It's a Slant thing. Even I don't understand.



1974 Duster, EFI /6 soon to be turbo...



Get that Monkay! Get that nasty thing!!

Engine is grounded with a number four cable running from the batt negative to to a bell housing bolt. The battery is in the trunk so the cable is longish. But it is heavy. It runs under the car along the frame..

Explain more about MSD HEI. Where to buy, etc. Do they simply plug in to same connections?

Tonight I will turn on filtering. I thought it was on. Thanks for noticing. I do not understand how those various choices inter-relate. CAn you chose all, or some, or just one at a time? And, I did not realize there was a master ON/OFF I had to chose to get the others to work. If it is off, it has been off from the start of the trip from VA Beach.

Here is an unrelated question. I do not want to hi jack my own thread here. When running in autotune, how does it handle the fuel over run cut off? Does it try to make those cells richer at the time over-run fuel cut-off is enabled? Or, does it "know" not to do this?

Sam

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In an e-mail from Peter, he is suggesting that interference would be less predictable, which lowers the spark plug interference as a suspect. He actually suggested widening the reluctor gap, saying there gets to be an interaction between an HEI module and the reluctor under certain conditions.

So now I am conflicted.

One of the guys at the cruise said that the old Mopar electronic distributors were notorious for getting weird when the bearings got worn. He is an older owner of a general, local auto repair shop, so speaks from a perspective of some knowledge and experience. I did not think the bearings felt worn, but then I have no basis for knowing what is acceptable here. I tend to be an optimist in these kinds of things, and end up deceiving myself myself.

Sam

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I got my MSD HEI Module at a local speed shop in Mesa, AZ (Loper's) but it looks like they only make a 4-pin. It was a plug-in affair. Now that I think about it, I lent it out to one of my race buddies and he never gave it back. Oh, well.

Ok, next grounding question. If I understand, you have run a cable all the way from the trunk to the trans/engine. How is the chassis grounded?



Turning noise filter on, which was off, turns off the tach interrupt masking, which was on. Tach period rejection, which was on, is independent and can be set either way.

When you set the noise filter on, it enables the next option under it in Basic Setup, which is Noise Filter Curve. Yours has some wacky values in it by default. I gleaned some sample numbers off the web that may be ok as a starting point. Most info I read said they just turned it on and it worked without messing with the curve. That would be my step 1.

Here's a screen shot of the Noise Filter Curve after I set it up with those sample numbers:

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It's a Slant thing. Even I don't understand.



1974 Duster, EFI /6 soon to be turbo...



Get that Monkay! Get that nasty thing!!

Well, I am sure he knows more about it than I do. I based my advice on the fact that I observed intermittent tach signals with too wide of a gap. But again, I am running a different setup than you are.

A worn out distributor will, among other things, let the reluctor gap vary as it spins. I could see how that could result in 'weird' behavior. I have seen them where the reluctor has actually hit the pickup and filed it down. More good reasons to eventually eliminate the distributor.

One thing I always worry about in a situation like this is the person asking for help gets bombarded with all kinds of often conflicting advice. Please understand that my suggestions are just that, suggestions. Like it says on the last page of the Messiah's Handbook, everything I say may be wrong.

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It's a Slant thing. Even I don't understand.



1974 Duster, EFI /6 soon to be turbo...



Get that Monkay! Get that nasty thing!!

Please don't assume, they asked you to check grounds as exactly stated. And there are many gotchas to watch out and installed correctly with MS systems.

This way less tedious and cut down discussions and such and solving problems faster.

Cheers, Wizard

I crimp and solder each connection (with heatshrink over the barrel)

I've found that just crimped connections can corrode at the copper connector interface.

I like using these for cable splices:
http://www.radioshack.com/product/index ... erPage=60#

With heatshrink over them, the wire diameter isn't huge at the splice.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

MSD modules are available in 4 and 7 pin. I have lots of experience with both. For the price they are excellent value.

I use a MSD 4 pin HEI in my bogger and regularly turn 6500 rpm with no miss. Stock ones tend to give up in severe situations......like high heat or high rpm.

There is no downside to a better module.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Measure the voltage input at the MS and HEI.
(during the problem would be ideal)

Also putting a large value capacitor on the power line to each component might help if there are voltage variances going into each box.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

You have no idea how much I appreciate you guys thinking about this and sharing your thoughts. Rest assured I am not pitting one guy against another. I come from a world rife with opinions. That being the piano world.

Would the capacitor go between the power feed and ground. Can you specify a capacitor size or value please. I feel like such a dummy on such basic things. And should I connect the positive side to the power wire?

Wizard, I wasn't sure what you were trying to tell me. I am open to whatever it was. Maybe you could elaborate a bit more.

Ed, I am pretty sure the HEI and the MS relay box are on the same fuse block. I will check.

Oh yes, the chassis is grounded via a number 4 cable run from the motor mount bolt to the radiator core support.

Thanks.
Sam

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