Another TI Ignition Issue

[Lawrence S.]

Here is one more picture

[Mark M.]

Does the engine run fine there and do the Tonawanda chisel marks on distributor housing flange to intake line up close? The 65 AIM for L78 upc 69 A11. shows the cap front center line aiming between #1 and #2 wire to front of engine. #1 wire is between vacuum can and the window area. Your rotor does appear too far! I just stabbed a 70 LT-1 TI and it lined up close to the marks. Timing chain seems a bit stretched so it may affect this. If you restab the distr. with rotor and oil shaft, turned counter clockwise 1/13 of a turn (if I remember right 13 teeth on the gear) the chisel marks may all line up at factory timing setting. I stab distributors with timing mark on 0 and rotor pointing at 1 cylinder tower and than turn distr. a bit for timing and check how close any original marks there may be. It looks like a nice car and hope you get to enjoy it soon.

[Lawrence S.]

Here are the chisel marks, alignment at 10* BTDC. Also reference of rotor button to 1 plug tower after I rotated the distributor 1 tooth CCW. Also VAC orientation.

[Mark M.]

It looks good. Hope your TI is all good. The LT-1 I'm doing now has corrosion in amp to harness plug and so all connections need to be checked and repaired as needed. Let us know how it runs. Duke and Richard are some of the best help we have here so you should be playing with that toy soon.

[Duke W.]

I had a TI on my 340 HP SWC from '68 to '75, but it was stored from late '71 to early '75 in my parents Seattle garage while the AF had me in North Dakota. The system was from the '67 "12-mile" L-88. The first time it quit circa 1970 I removed the amp and cover and found one of the three main power transistor leads had broken off the circuit board, so I stuck it back in the via, added a drop of solder and it worked.

The second time it quit (crank but no start) was 1975 after I moved to California and brought the SWC down from Seattle. it was exfoliation corrosion on one of the harness pins on the harness connector to the amp like you reported.

By that time I had figured out how to make the OE single point provide a reliable spark to 7000 revs. So I took off the TI, installed the OE vacuum advance, weights and springs on and put everything in box. It still had the brown copper terminal distributor cap.

In 1988 I sold the system to David Burroughs who was at that time the owner of the L-88 it came from.

I love these simple electro-mechanical analog cars.

Duke

[Lawrence S.]

I spoke to Duke about this. I had to reseal the carb, pulled off the ten old plus year old paper gaskets that were near glued to the carb. While doing so replaced the old power valves with the ones I had on hand. I had a 7.5" on hand for the primary replacing an 8.5" and replaced a 6.5" for the same. Put the carb back together and tried to start the car. Had a terrible flooding situation. Pulled the carb, rechecked, and pulled a little paper gasket residue out of the carb installed tried again same problem. Thought about it and the only thing other than gaskets that I had changed were the power valves. Apparently, the 65 metering blocks take a power valve that has a little shorter threaded section. So I had fuel passing through the primary power valve and slightly passing through the secondary power valve. To remedy this (I did not know this) use the thick nylon gasket in your kit. The thick gasket makes up the difference. I did not learn this gasket detail until I reinstalled the old power valves. They worked fine and should had never removed them. (Don't fix what is not broken) So after letting the gas evaporate from a soaked engine not once but twice, and after pulling all the plugs to confirm evaporation to make sure the car was dry, and changing the oil and filter felt like I could try and start the engine. At 10* on the timing mark and the chisel marks on the intake and distributor aligned the car finally fired. Glorious sound, L78 with NOS side pipes!
Its very rainy here and wet so I have not taken it out for a drive. Happy finally to have the original distributor back in the car, what appears to be adjusted so the car is happy and can fine tune from here. Thanks to Rich Mozetta for many calls and Duke for the final coaching. I am not out of the woods yet so will update when I can get the car hot and drive it.
Lawrence

[Lawrence S.]

Hi Guys,
I have not abandoned this thread just busy with one daughter’s wedding and a grand baby born yesterday so busy.

I did get the distributor stabbed correctly, car fires right up cold, but once hot it does not want to start, and had loose valves. So got the valves adjusted and was on the way to map the timing but developed a miss. Pulled all the plugs and number 5 looked like it was not firing. Pulled the spark plug and confirmed there was spark at the plug, but it was really weak in my opinion. With the car running I pulled number 5 plug and really saw no meaningful idle drop off. Tried a few other plug wires and on some of them same as number 5 but others saw a larger arc and a slight idle drop off. I thought the amp may be going bad so bought a new green board installed it and same result. Re-installed the GM board same issue. I have confirmed good ground at the amp. Given the TI harness is original, 60 years old, I have a new one coming from Zip (Lectric Limited brand). Once it gets here I hope that cures my problem. I really want to get this car dialed in, and drive it.
To digress for a moment, this engine sat for 20 years with only break in miles on it. When I first got it fired up and running it ran ok, but the timing was too advanced and would die once I tried to retard it and it would not start or hard to start after it got hot. So this issue has been there since I got the car running again.
Happy 4th to everyone and hope to be cruising soon.
Lawrence

[Duke W.]

Something else to check is plug wire resistance. I believe the OE type RFI wires are the same as the small block other than on the big block they are shielded by the woven stainless steel sleeves that are grounded as opposed to the small block's external shielding.

OE type RFI suppression wires should exhibit no more than about 5000 ohms per foo t,and there are many reports that the "reproduction" wires are poor quality and break down soon.

I don't know what wires you have on your engine... OE? Repro? Some aftermarket substitute... but try to figure out what you have and definitely measure and record the resistance of all plug wires plus the coil wire and compute the resistance per foot. Also verify that the terminals on both ends are properly crimped on with good electrical continuity.

Duke

[Lawrence S.]

Thanks Duke-I failed to mention that I did test number 5 plug wire resistance and it was 10,700 ohms and two feet long. I read that 6,000 ohms per foot was the upper range. I did not measure resistance on the other wires. I will do so and record it.

Lawrence

[Lawrence S.]

Guys,
Here is the latest update:
Distributor is stabbed correctly
I have the initial timing at 13* BTDC
Idle mixture screws are set richer than 1.5 turns but not by a ton. I believe I had the idle mixture screws too lean previously while trying to set initial timing.
I installed a new “green” amp board in the amplifier.
I installed a new TI harness. The car had the original I am fairly certain
I adjusted the valves, .020 intake and .022 exhaust
I removed the stiff distributor weight springs I had previously installed and installed the springs that Mike Zamora had in the distributor once I got it back from his restoration.

I still need to map the timing which I will do over the next few days and post results here.

Here are a few things I learned. My TI distributor is very sensitive, adjusting the distributor 1* may result in 2-3* ignition timing. While solving for my initial I believe I was too aggressive in the adjustment.
I had my idle mixture screws too lean which may had contributed to engine stalling while retarding the ignition
I started to question my timing light, so went and pulled out my old Craftsman timing light, (old style dial back) it seemed to work better than the Innova Chinese product.

Duke and I chatted about the current VAC MS 355, and he suspects it will not pass the 2” rule and he is likely correct. Off idle the car is a little sluggish. Once engaged the car runs well. I have a MS 201-15

Once the timing is mapped will post results.

Best of all to report, I went on a ten mile ride and the car did just fine.

Thanks,

Lawrence

[Lawrence S.]

Ok this is my timing map as I understand it.

With the car turned off and with my mighty mac, I have my VAC all in at 12". The distributor plate starts to move at 5"
Vacuum with car idling at 900 rpm I have 10" of vacuum. So the VAC fails the two-inch rule. I need a different VAC. I mentioned the slow off idle response of the engine last night in my post and I suppose this is the case.

Initial timing is 12* at 825 rpm. I know I posted 13* @ 900 rpm last night but that was at a slightly higher idle and I am not using a digital dial back and old school with numbers on the dial so the tolerance may be 1*

VAC plugged in I have 27* at 1,000 rpm

Mechanical

1,000 RPM 14*
1,500 RPM 23*
2,000 RPM 30*
2,500 RPM 36*
3,000 RPM 39*

Lawrence

[Duke W.]

The OE L-78 VAC is the 201 15, and that one doesn't pass the two inch rule due to maximum advance being nominally 15* @ 15.5". I'm not sure of the specs for the "355" (I think it's 15* @ 12".) , but check how much vacuum it takes to pull to the limit.

Your idle vacuum seems low, Typical is 14" @ 900, but that may be for the looser '66 valve clearance specs. The tighter '65 specs you are using would tend to reduce vacuum at a given speed, but I wouldn't have expected it to be that much. It could also be that the cam is aftermarket with higher overlap. That's what I ran into on the L-78 I worked on a few years ago and reported on here in a thread I started.

You probably need a B28 VAC, but do a local purchase and check that it takes nominally 8" to pull to the limit. Many are reported to be way out of spec.

It's very important that the VAC remains locked at full advance at idle speed. Otherwise there will likely be an idle stability issue. As the VAC retards you loose idle speed which causes further loss of vacuum and advance and engine speed, and the engine will eventually stall if you don't blip the throttle every 30 seconds or so. That was why my SWC's 340 HP engine would not idle stably when new. Even with the idle set at 900 the Duntov cam didn't pull enough vacuum at idle to keep the 201 15 VAC pulled to the limit.

1963 was the first year vacuum advance was used on mechanical lifter engines and they screwed it up. My 340 HP engine as above and using ported vacuum advance on the FI engine. They fixed it for '64 with a 8" VAC and full time vacuum advance for both the 30-30 cam engines and a much more aggressive centrifugal. In 1965 I installed these parts on by 340 HP SWC, and they solved the idle stability issue and made for noticeably increased low end torque, and that's how I came up with the "Two-Inch Rule".

I'm surprised that you are able to implement such an aggressive centrifugal curve with as much initial as you report. In my experience big blocks don't like as much low speed, low load advance... too much results in low speed/load "trailer hitching", but that may be because SB mechanical lifter cams have more effective overlap, which means greater low speed/low exhaust gas dilution, which slows combustion propagation, so they like lots of idle and low speed/low advance, but since your engine has 30-30 cam idle behavior maybe that's why it will tolerate a more aggressive spark advance map than a L-72 with the OE cam and looser than '66 valve clearance specs.

Duke

[Patrick H.]

Your idle vacuum seems low, Typical is 14" @ 900, but that may be for the looser '66 valve clearance specs. The tighter '65 specs you are using would tend to reduce vacuum at a given speed, but I wouldn't have expected it to be that much. It could also be that the cam is aftermarket with higher overlap. That's what I ran into on the L-78 I worked on a few years ago and reported on here in a thread I started.

Have the idle mixture screws been adjusted to obtain maximum vacuum? It seems like they've been played with, but not optimized, based on the posts yesterday. You might gain up to 5" vacuum with proper adjustment.

[Lawrence S.]

Camshaft is OEM 143 per the engine builder.
I will readjust idle mixture screws with a vacuum gauge. I used idle speed previously but likely could had spent more time on this process.

[Lawrence S.]

I changed the springs to what I thought may be just a tad tighter. Likely negated the tighter springs with the 2* initial advance

28* 1,000 rpm with vac plugged in
11” of vacuum at 1,000 rpm, no meaningful difference from 12* initial
I did tune the idle mixture screws to 1,000 rpm, it is a little richer now. Not sure if that give it a crispier start or not?

Mechanical Advance, no vac plugged in

1,000 17*
1,500 24*
2,000 32*
2,500 36*
3,000 41*
3,500 42*
4,000 42*
4,500 Light started to scatter. Distributor is restored and Zamora had good readings all the way to 6k, so perhaps Chinese timing light??

At 12* initial and what I thought were a little weaker spring had these results

Mechanical, vac plugged
1,000 14*
1,500 23*
2,000 30*
2,500 36*
3,000 39*

No readings above 3,000 with that setup. I was using the older Craftsman light.

Question, with vac plugged in and run the 14* initial and cruising at 3,000 rpm, I would be at 56* all in. That is too high, correct? What should my all in timing be at say 3,000 rpm

Thanks

Lawrence