Delphi TBI distributor discontinued(?). What's next best option?

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Schurkey

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Accel and MSD both make aftermarket versions of the TBI and MPFI big block distributor. Myself, I would pay for the MSD as their distributors are built to handle the high output spark of the MSD ignition boxes.

https://www.amazon.com/MSD-Ignition...Y1KAX2JTJDW&psc=1&refRID=2HP7XQ03RY1KAX2JTJDW
First Guess: Neither Accel nor MSD "make" those distributors. They "import" them from the same Communist nation that build the junk parts the competitors sell. Possibly made in the same factories, just packaged in different boxes.

There was a time when the MSD "Street Fire" line was intended to be the bottom-feeder, mass-market, low-cost alternative to the 'real" MSD line of products. Unfortunately, much of the "real" MSD product catalog is made in China now. All of that is crap.

It got sooooo tired of burning through the rotor of a stock HEI on my MSD equiped crew cab.
There's something wrong with your vehicle. I ran MSD spark boxes on multiple vehicles, from a Honda Civic, Dodge Slant 6, SBC Tri-Power 400, and my '88 5.7L K1500 among others, and never had a problem with "burning through" OEM and aftermarket rotors, caps, wires, etc.

Your plug gap is too wide, or the rotor-to-cap gap is too wide, your plug wires have failed (High resistance) or (on the older, coil-in-cap distributors) you need a low-resistance "button" between the coil and the cap.
 

whiteboyslo

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***UPDATE***

Vehicle is back from the mechanic. DUI distributor is in. I went ahead and swapped the Delco ICM onto it before he installed it since the only minor gripes I could find on the DUI was in regards to premature ICM failure (seems like these trucks really only like Delco ICMs). And yes, I remembered the thermal paste. I used a generous amount of some 'good stuff' I got from the computer store.

I haven't driven it far enough to see it for myself, but the mechanic said his guys drove it and thought it was still acting up.

Here's where it gets interesting... While diagnosing a coolant leak before dropping it off the other day (bypass hose), I found a piece of plastic vacuum tubing sitting on the intake manifold. I looked all over and couldn't figure out where it went, so I brought it to the mechanic and asked his $.02 on it. When I picked it up, he told me his guy accidentally snapped the vacuum tube running to the EGR valve while installing the last distributor but had replaced it with some rubber hose.

So now my theory is that the last distributor was probably fine, albeit probably on borrowed time since the parts store distributors generally don't have a sterling reputation for reliability. For that reason, I'm not upset about throwing in a (hopefully) better unit. What I think is going on is that the vacuum used to actuate the EGR is actually enough to collapse the rubber hose instead of actuating the valve, which explains why it only misbehave under specific conditions (part throttle cruising).

I'm assuming the stock parts are long since discontinued, so it looks like a trip to the Dorman HELP! section is in my future.

Any thoughts on this theory? Can I confirm with my scan tool? If so, what values am I checking to confirm this?

Thanks!

Mike
 

whiteboyslo

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Aha! I figured it out! So, when the mechanic broke the vacuum line, he didn't just replace the line from the solenoid to the valve. He also replaced the line from the TBI to the solenoid. Problem is, he swapped the lines at the solenoid! Minor goof, I guess, but the diagram is right on the air cleaner staring you in the face. This same "mechanic" also left half the intake tubing unbolted with the bolts hanging on the cowl, so in all it looks like a rush job that bit everyone in the butt.

Anyway, she's running great! No more surging!

Mike
 

L31MaxExpress

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I would have used the DUI module myself. About half the Delco modules retard the timing up to 4° above 3,200 rpm and make the engine a dog power wise. DUI module is also built to give more spark energy via increased dwell time.
 

whiteboyslo

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I would have used the DUI module myself. About half the Delco modules retard the timing up to 4° above 3,200 rpm and make the engine a dog power wise. DUI module is also built to give more spark energy via increased dwell time.

Huh. Might explain why Summit made me click a bunch of buttons assuring this was off-road use only (thanks, CA). Maybe I'll throw it in if/when I throw in their coil and some new plugs.

Thanks for the info!

Mike
 

L31MaxExpress

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Huh. Might explain why Summit made me click a bunch of buttons assuring this was off-road use only (thanks, CA). Maybe I'll throw it in if/when I throw in their coil and some new plugs.

Thanks for the info!

Mike
California laws are retarded. As for the stock GM modules. The difference between the good one and bad one is 6° timing at 4,200 rpm.
 

Schurkey

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California laws are retarded. As for the stock GM modules. The difference between the good one and bad one is 6° timing at 4,200 rpm.
I've seen where that info comes from, and I have to say that I'm skeptical. Yes, RBob is a noted authority.

The "good" and the "bad" modules are considered interchangeable in the aftermarket, and by "aftermarket", I mean everyone and their brother including AC Delco. If they REALLY screwed-up the timing, the EPA would be all over them for emissions and for CAFE-Fuel economy violations.

But I didn't do the research, and until I do my own verification, which is currently scheduled for the 23rd of Never, I can't absolutely dis-prove what the guy is promoting.

The larger story is that there's a factor affecting timing advance built-into the ECM software called "Latency"; and some of the advance problems have to do with "latency" tables interacting with the electronics within the ignition module.

https://www.thirdgen.org/forums/diy-prom/465232-ebl-sa-latency-table.html
 
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DerekTheGreat

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Accel and MSD both make aftermarket versions of the TBI and MPFI big block distributor. Myself, I would pay for the MSD as their distributors are built to handle the high output spark of the MSD ignition boxes. It got sooooo tired of burning through the rotor of a stock HEI on my MSD equiped crew cab...
That's funny because about 10 years ago I swapped out the heads, intake and ignition system on my Firebird. I put in MSD's billet HEI dizzy along with their coil and cap. I went through three of their coils before I put the stock one back in (Such a joke as after the first one went I kept the original in the compartment in the hatch) and then their cap failed while I was trying to pull out into traffic. That could have ended badly.. But it burned right through at the coil lead. Their stuff is junk IMO, it's a wonder the 6AL box still works...
 

L31MaxExpress

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I've seen where that info comes from, and I have to say that I'm skeptical. Yes, RBob is a noted authority.

The "good" and the "bad" modules are considered interchangeable in the aftermarket, and by "aftermarket", I mean everyone and their brother including AC Delco. If they REALLY screwed-up the timing, the EPA would be all over them for emissions and for CAFE-Fuel economy violations.

But I didn't do the research, and until I do my own verification, which is currently scheduled for the 23rd of Never, I can't absolutely dis-prove what the guy is promoting.

The larger story is that there's a factor affecting timing advance built-into the ECM software called "Latency"; and some of the advance problems have to do with "latency" tables interacting with the electronics within the ignition module.

https://www.thirdgen.org/forums/diy-prom/465232-ebl-sa-latency-table.html
I have done my own testing. Found the same results. Noticeable difference in my 1/8 mile and 1/4 mile times as well.
 
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