Suspected TI issue - 1971 LT1 - original TI parts

[Richard M.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

James, Any progress?

I spoke with Dave Fiedler today about plug wires. He again advised against solid core wires with TI, particularly if using resistor plugs. He said it causes erratic ignition issues. Some of his customers confirmed. But likely unrelated to a ignition no-start condition.
He also said that solid core wires were not originally used. Maybe on the no-radio L88's. I'd look it up, but away from my books and gmpartswiki.com is down.

Rich

Edit 1: Some more I've learned since I initiated the plug wire discussion. I wanted to follow up with factual data. It seems GM thought this out as Dave reiterated to me.

Here are a few pages from the wiki P&A 14(1981), showing plug wires and plugs. Appears to show 1967+ "HD"(L88)? used different (not listed as "GLASS INTERBRAID") wires. I take it this means "solid core".


L88 also used AC43N plugs. Are these non-Resistor? I believe so.

But, it shows R43XL for Alum Head. A bit confusing as th "HD" L88 isn't listed.

Also notice the 1971 350 SHP(LT1?) info for wires and plugs. It originally used GLASS INTERBRAID wires and Resistor plugs.

Screenshot_2023-10-10-04-51-34.jpg

Screenshot_2023-10-10-04-47-07.jpg

Edit 2: I found photos of the HD L88 8909665 wire set. They're marked...

"Delcore TV-R SUPPRESSION" Is this solid core? Unsure, but read further...

Screenshot_2023-10-10-06-22-11.jpg
Screenshot_2023-10-10-06-20-22.jpg

Edit3: Further analysis has me convinced that the use of non-suppression(solid core) plug wires is a recipe for problems with TI. Specifically, as shown above, GM used the 8909665 Delcore TVR Suppression wires for HD (L88/ZL1), which I discovered are a special core with unique shielding to eliminate the effects of EMI/RFI in electronic ignition systems. I looked for detailed ohms per foot data, but not found. I believe. TV-R is the Delco acronym for Transient Voltage "Reduction". Or ?

Good read here related to EMI/RFI ....

https://www.onallcylinders.com/2022/04/14/what-is-emi-rfi-and-how-can-you-stop-electric-ignition-interference/

P.P.S. Dave and i had a nice long talk about TI in general. We talked at length about TI modules. He uses the M&H (black potted) TI modules in all of his restorations. They've been making them since 1992 and have a very good track record per Dave. We also talked about the K&B (green open component) TI modules, and that I have used those exclusively, also a very good track record for me. Since Ken Anderson's passing, Ken's wife Barb has continued the business, albeit not as an extensive range of parts as before according to Dave. The website is inactive but Dave said Barb can be reached by phone.

[Richard M.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Note edits to previous post.

Rich

[Dave S.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

A 263 TI coil comes original with a 1971 LT1?

[Patrick B.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Richard-- Your latest posts got me thinking. I had problems with my dial-back timing light when timing the 67 big block with Packard 440 wires. So I had to use my old Sears timing light (that we all have stuffed in an old tool box). The timing was fine with the old light. I seems to me that the EMI may well be affecting the modern timing light, making the spark seem erratic. However, I think the radiator support was shielding the GM TI amp from the EMI because the spark looked normal with the old Sears timing light. Oddly enough the dial-back timing light worked fine on the 70 Corvette with the 30 year old Moroso solid core wires. I even transferred the number 1 wire from the 70 to the 67 but that did not solve the problem with the dial back light.

The 67 is the quickest starting 427/435 I have ever experienced so I do not think the wires have anything to do with James' problem. But I now believe the EMI affected my modern timing light. I was prepared to believe that the very old 207 coil was erratic, but the car runs so well I was not motivated to change it.

Also, I thought that the 67 L88 wires were red not like the black wires listed for no radio cars. Maybe an L88 expert can respond to educate us.

[Richard M.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Richard-- Your latest posts got me thinking. I had problems with my dial-back timing light when timing the 67 big block with Packard 440 wires. So I had to use my old Sears timing light (that we all have stuffed in an old tool box). The timing was fine with the old light. I seems to me that the EMI may well be affecting the modern timing light, making the spark seem erratic. However, I think the radiator support was shielding the GM TI amp from the EMI because the spark looked normal with the old Sears timing light. Oddly enough the dial-back timing light worked fine on the 70 Corvette with the 30 year old Moroso solid core wires. I even transferred the number 1 wire from the 70 to the 67 but that did not solve the problem with the dial back light.

The 67 is the quickest starting 427/435 I have ever experienced so I do not think the wires have anything to do with James' problem. But I now believe the EMI affected my modern timing light. I was prepared to believe that the very old 207 coil was erratic, but the car runs so well I was not motivated to change it.

Also, I thought that the 67 L88 wires were red not like the black wires listed for no radio cars. Maybe an L88 expert can respond to educate us.

Interesting... I too never thought much about the EMI issues, but you've enhanced my thoughts now again. Yes, as I mentioned, not related as James' smoking gun, only a info tidbit when he gets it running.

On your '67...

Are you using the full distributor shielding along with the ground shield sheathing on those solid core plug wires?

Are you running non-resistor plugs?

Maybe some of the reasons you're not having TI:EMI issues.

I recall the factory '67 L88 wires were Gray(maybe with Orange boots?). Service replacements were black, as I pictured earlier.

Rich
P.S. James, sorry if I've gotten us a bit off track, but waiting to get back into diagnosing your no-start issue when you get back to it.

[Richard M.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

I recall reading they were a type of wire used on light aircraft engines... likely "solid core" with near zero resistance.

Duke

Duke after thinking more about how EMI affects electronics, as well as electrical/electronic gauges, i suspect they're special anti-suppression wires.

A few aircraft plug wire searches tell me wires are apx 1kOhms/ft, so likely not solid core. Wire is about $20.00/ft. One spark plug is about $140.00. I found a plug install/maint document...it's 28 pages long.

I GGL'd "aircraft spark plug wire specifications"


Rich

[Patrick B.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Rich — I put the Packard 440 wires in the stock woven sheathing grounded to the valve cover bolts, but I do not use the distributor shield. I think the plugs are Champion RN12YC. I don’t think you can get non-resistor plugs from Champion any more. It doesn’t make sense to me why resistor plugs would be an issue operationally. With the plug resistance and the wire resistance in series, what difference would it make where the greater resistance is coming from.

I am going to my garage today to see if I can repeat my timing light observations. At the time, I just thought my new dial-back timing light was failing. I actually returned it for another one, and the same thing happened. I gave up on them and thought they were junk. Now, I have a new insight. Maybe covering the timing light with grounded aluminum foil would change its performance if it is not actually damaged.

[Duke W.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Thanks for the research, Rich. It makes sense that aircraft spark plug wires are RFI shielded as EMI could affect VHF comm and nav aids, but 1K ohms per foot is a lot less than the 10K per foot of typical automotive RFI wires.

My '88 Mercedes 2.6L OHC I6 has zero resistance wires, but 2K resistors built into the cap and plug terminals that also have metal shields around the boots. I had to buy a special tool to remove them from the plugs without risk of damage.

Also non-resistor plugs were OE. At the first plug change I installed Bosch Platinum plugs (resistor type only available) that I thought was an "upgrade", but noticed a bit of idle roughness and the next emission test showed a significant increase in HC emissions. Apparently the increased resistance robbed energy and/or altered the voltage wave form so as to increase the number of random misfires to where I could feel them at idle and causing increased HC emissions.

So I got rid of the Bosch Platinums and installed OE equivalent non-resistor "two-dollar" Bosch copper cores plugs equivalent the OE plugs. About 15 years ago when I found out that Bosch was discontinuing non-resistor plugs I bought a lifetime supply.

Duke

[Patrick B.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Rich and Duke—- I am at my garage and just did the test of timing lights again. I tested with 2 427 cars.

One is my 1970 LT-1 car with a detuned 1969 ZL-1 427. It has the stock LT-1 491 distributor with GM 236 vac (like a B28), the original 53 year old TI amp, and a newer GM TI coil with a painted 207 part number. The plugs are Champion 2319 advertised as having resistors to reduce EMI. The plug wires are Moroso Blue Max purchased in the 1980’s. I think they are completely different from the Blue Max wires sold today. New Blue Max wires are advertised as spiral wound stainless steel around a Aramid core. They have a resistance of 800 ohms per foot. That would seem like a glorified carbon wire. The old Blue Max wires on my car have a resistance of only 1 ohm for a wire about 3 feet long, so I think they must be solid core. The test of timing lights was to measure the timing at 800 rpm with and without the vacuum advance connected. 800 rpm was about a low as I could keep it running steadily without the vacuum advance. First with my old Sears Penske light I measured 10 degrees static advance and 30 degrees with the vac connected and the idle adjusted back to 800 rpm. I have old fashioned timing tape on the balancer so the 30 degree advance could be read accurately with the simple timing light. Next, tried the Innova 3568 dial-back timing light. It read the 10 degree static advance perfectly and also the 30 advance with the vac connected. The dial-back feature and the tachometer also worked perfectly. I also tested a cheap Actron CP 7529 and all its features worked fine. I was a little surprised that the GM 236 vac gave me 20 degrees advance when it was only labeled 16, but all three timing lights agreed and there were no erratic sparks.

The next car was my 1967 L-71 with the Packard 440 wires in original sheaths. It has the original 258 distributor, an old embossed GM 207 TI coil, and a NOS GM TI amp that I put on it for peace of mind even though the original amp still worked. I was wrong about the spark plugs in my last post. They are Champion N12YC - NOT resister plugs. I started the car and got it idling very smoothly at around 700 rpm with the vac line plugged. The old Sears light read the static advance at 8 degrees on the timing tab (no timing tape on this car but I am reconsidering). Next I put the Innova 3568 on it without turning the engine off and read the same perfectly steady 8 degrees on the timing tab. I was going to try the dial-back feature when I noticed that the screen had turned blank. I turned the car off and disconnected and reconnected the power to the timing light. The screen came back on, but when I started the car again the screen went out and it did not flash. I tried that number of times and the Innova would not work with the engine running. Next, I tried the Actron. It would not flash at all. The screen lit up but tachometer and other features would not work.

Conclusion- The combination of solid core wires and non-resistor plugs caused modern electronic timing lights to malfunction but the engine ran very smoothly even at a low rpm with the vacuum advance line plugged. The only apparent difference between the ignition systems on these two cars was that one had resistor plugs and the other did not. I plan to continue this examination by swapping the plugs from one car to the other. If that makes no change, I will swap the wires from one car to the other.

This question interests me because I plan to put the LT-1 engine back in the LT-1 car. The spark plug wires on a small block are such a pain in the ass to change I made a set of Taylor solid core soldered terminal wires for durability that I plan have pre-installed on the engine when it goes in. However, it would be nice to be able to use a modern dial back timing light.


Clearly, I do not believe that solid core wires make a GM original TI system malfunction with resistor or non-resister plugs. I used to drag race the 70 ZL-1 in club events and test and tune nights with non-resistor plugs, and it ran fine at 6500+ rpm. In fact, if you have old Restorer magazines you will find that it ran the fastest time of the day at the 1988 NCRS national convention in Lancaster PA with the same wires, TI amp, and coil. Yes, a drag race at Maple Grove was an official NCRS event at that national convention. But that was back when a mid 12’s street car was considered fast.

[Richard M.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Thanks for the research, Rich. It makes sense that aircraft spark plug wires are RFI shielded as EMI could affect VHF comm and nav aids, but 1K ohms per foot is a lot less than the 10K per foot of typical automotive RFI wires.

My '88 Mercedes 2.6L OHC I6 has zero resistance wires, but 2K resistors built into the cap and plug terminals that also have metal shields around the boots. I had to buy a special tool to remove them from the plugs without risk of damage.

Duke

Your post got me thinking about how to fix a engine with EMI issues at a altitude of 10,000 feet, so off I went on the hunt. I thought BOATs were expensive. (Bring Out Another Thousand)

.....

Rich and Duke—- I am at my garage and just did the test of timing lights again. I tested with 2 427 cars.
.
.
.

Clearly, I do not believe that solid core wires make a GM original TI system malfunction with resistor or non-resister plugs. I used to drag race the 70 ZL-1 in club events and test and tune nights with non-resistor plugs, and it ran fine at 6500+ rpm. In fact, if you have old Restorer magazines you will find that it ran the fastest time of the day at the 1988 NCRS national convention in Lancaster PA with the same wires, TI amp, and coil. Yes, a drag race at Maple Grove was an official NCRS event at that national convention. But that was back when a mid 12’s street car was considered fast.

Great test effort Patrick. Thanks for doing that. Maybe the heat sink, grounded case for the TI Amp helps with the transient voltage suppression. But it is pretty far forward on the cars on the front wheelwell skirts. Maybe that's why they put them way up there, away from the ignition wires. On the 64/65, they're mounted on the core support, front side. The core support metal likely shields EMI too.

It'll be further interesting to see what happens when you swap that hardware between the cars.
.....
Rich

[James G.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Duke,
Interesting on the Benz plug wires and 2k resistors.
I didn't have a figure for the resistors, but I had read somewhere that if you ran solid cores with resistance plugs on a high energy ign you needed to solder an inline resistor.
I am going to have to figure out where I read it.

It has not failed to start again.
I have the board on the way which I will probably throw in the car tool kit along with the spare TI coil.

Even feed back hands down beats the original plug wires I removed last year... one with zero continuity, one with 250k, and one with 195k the rest in spec.

I am highly inclined to go the inline resistors route as I have not had very good luck with reproduction spiral wrapped linen core wires. When compared to an original GM set from the 70's the spiral wrap is NO WHERE NEAR as robust in both wire gauge and number of turns per inch around the core.

[Bill B.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

After much research, I decided to install Accel 8 mm black ferro-spiral core wire set (#5042K) for small block), 500 ohms per foot resistance, coupled to Denso Iridium Power (#ITF16TT) which had 5 kOhm of resistance. No issues in performance with the TI. Idles good, no misses up to and beyond 6,500 rpm. Installed the green K&B board in the TI Amp and a good 207 ignition coil from Dave S. (had experienced intermittent issues when hot with the repro GM 272 China coil)

The only slight concern during installation was the 8 mm jacket was a little tight in the wire looms at the bottom of the "V" shielding going to the front plug set. Ditto on the rubber grommets and looms near the distributor. (they apparently don't make a fitted set in 7mm size) Have been running this configuration for the last 8 months, but so far, no issues, no complaints.

Let the reader beware that this is NOT an NCRS TFP configuration.

[Patrick B.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

James, Rich and Duke --- I performed more tests to follow up on the observations I made in comment #24 regarding the use of solid core wires with the Corvette C2 and C3 TI ignition systems. In the previous comment I described a 70 TI Corvette with solid core wires and resistor plugs that ran fine and whose spark timing looked normal using a variety of timing lights. In contrast, I described a 67 TI Corvette that also ran fine with different solid core wires and non-resistor plugs whose spark timing looked normal with an old Sears timing light with a direct alligator clip connection, but which caused 2 modern timing lights with magnetic pickups, dial-back capability and tachometers to malfunction. I performed various tests, but the main result was when I installed in the 67 Corvette the Champion 2319 resistor plugs I took out of the 70 Corvette, the problems with the modern timing lights went away. The combination of solid core wires and non-resistor plugs apparently created an EMI condition great enough to disrupt the operation of the 2 kinds of dial-back timing lights I had, Innova and Actron. However, the combination of solid core wires and resistor plugs did not disrupt the dial-back timing lights, presumably because that combination produced less EMI. Neither car had any erratic spark problems with the original GM TI boxes (with ancient Germanium transistors) and solid core wires, regardless of the type of spark plugs. The only issue was the measurement of spark timing with modern timing lights that were adversely affected by the combination of solid core wires and non-resistor plugs.

James-- Have you ever tried to measure the spark timing of your LT-1 with solid core wires? If it looked erratic or your timing light shut off, use resistor plugs. I don't think you need to add any clunky resistors in line, just use simple cheap resistor plugs. I measured a new AC R45S plug at 5K ohms. I am going to use those with the solid core soldered Taylor wire set I made for durability with my LT-1 engine.

Rich --- My tests fly in the face of everything Dave Fiedler told you. According to his advice to you, the combination of an original GM amplifier, solid core wires and resistor plugs should be the worst. Instead, it seems to be the best if you want the sure durability of solid core wires, especially on a small block where the wires are subject to lots of heat and are hard to replace. This surprises me because Dave Fiedler is regarded as the number 1 expert on Corvette TI ignition. Could his warnings apply more to the modern replacement amps? The modern timing lights were certainly more vulnerable to EMI than the old Sears timing lights. I even tried a slightly less old Sears light with a magnetic pickup to see it the alligator clip connection of the first light was its reason for success. But both old Sears lights worked fine even with the non-resistor plugs.

Duke --- When I installed the used resistor plugs in my 67, it seemed like the idle speed went down at least 150 rpm. The engine had cooled during the change, and I was testing the timing with and without the vacuum advance. But, I think when I was finished I still had the throttle screw down further to achieve the same idle speed and the idle seems a little less steady. Could resistor plugs cause this change? The Champion resistor plugs had about 12k ohms with a variation of 2k to 3k. So, much more resistance than the AC plugs.

[Richard M.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

Patrick, Great effort with this. Thank you.

Since your test results seem to conflict with Dave's advice, all I can think of is that there were some other conditions with his customers' cars that experienced problems with the solid core wires and resistor plugs. He himself had not experienced it on actual cars, but was told this by several users of his restored hardware. He wanted to share those experiences at the time, and again recently in another conversation we had after our discussions here. That's why I brought it up originally. I still think it's a good thing for others to be aware of the possibility of solid core wire usage problems.

But what's good to know is your EMI issues with the digital timing lights, and it reminded me of something. I too had a problem with my Actron dial-back TL when running TI in a '67 on a L71 mounted only on chassis years ago for engine break-in. As I recall the Actron display went dead and I verified it still had power etc. Engine had braided stock LL repro wires and stock AC43N plugs. But no distributor shielding. AMP was mounted on a bracket next to the left rear cylinder bank. You can see the AMP below my panel & oil gauge below.
DSCN2951.jpg

I ended up buying another Actron as I thought mine was broken. I'll never forget that as I used my '07 Corvette AT coupe to pick it up at my local Auto Zone that afternoon, and as I went to leave, my console shifter cable bushing had broken, unknowingly when I got there. I went to leave and I couldn't shift it out of Park. I had to get rescued by my son and trailer the car home that day.

Later, that new Actron worked fine. It must have been a EMI problem with the other one and it wasn't bad. I still have that one and for a test I used it some time later on a C1 points distributor setup, and surprisingly it still worked fine, and still does. The 1st one was never bad. So now I have 2 Actron TL's.

Again, thanks for your test efforts. Great work!

Rich

[Duke W.]

Re: Suspected TI issue - 1971 LT1 - original TI parts

"Duke --- When I installed the used resistor plugs in my 67, it seemed like the idle speed went down at least 150 rpm. The engine had cooled during the change, and I was testing the timing with and without the vacuum advance. But, I think when I was finished I still had the throttle screw down further to achieve the same idle speed and the idle seems a little less steady. Could resistor plugs cause this change? The Champion resistor plugs had about 12k ohms with a variation of 2k to 3k. So, much more resistance than the AC plugs."



I don't recommend resistor plugs on models that did not have them as OE, however, when resistor plugs became OE in '69 I know of no significant changes to either the single point or TI ignition systems.

Lots of guys run Delco resistor plugs because Delco no longer offers non-resistor plugs, and I don't recall any poor performance complaints.

So given the above I don't see how resistor plugs could knock 150 RPM off idle speed.

I've always run OE ignition components other than a brief period with Packard 440 wires on my 340 HP SWC back in the sixties. That was part of my attempt to solve the constant ignition breakup as low at 4500 RPM, but the there was so much radio noise that I replaced the with the OE radio suppression type wires after no more than a year.

Hotter AC 45 plugs helped, but I ultimately figured out how to "blueprint" the distributor, replaced the wobbly breaker plate, shimmed up the sloppy end play, and installed 28-32 oz. breaker arm tension points, and the old single point delivered a reliable spark to 7000 revs without missing a beat.

It's all in the details!

Duke