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tii timing & distributor


cpolyak
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"If it's not broke, don't fix it." Should have listened to whomever said that.

 

My 73tii was running fine, but I decided to swap points for Pertronix yesterday. With the help of a local 2002 guru, we completed the swap and reset timing at full advance to 36-38 degrees (slightly higher for altitude here in Denver). Distributor is a Bosch 013 - there was a little play/rattling in it, but nothing that made me question it's proper operation. The engine was warm when the swap and timing were set. I drove 25 miles home, no problems. 

 

This morning the car started right up. Slow drive through neighborhood was fine, but when I accelerated up a small hill on main road the engine started chugging/struggling. The surging was most pronounced between 2000-3500 rpm and when under a moderate to heavy load (acceleration). Got the car up to full temp and these symptoms persisted. Also noted idle is rock solid cold or warm at 850 and car starts right up cold or warm with minimal cranking. 

 

Now I'm wondering a few things:

1. Could too much advance be causing this? 

2. Could original distributor be shot? If so, thoughts on Irelands mechanical advance tii distributor vs. 123 tune? 

3. What would cause car to run fine after the swap, but then stumble so much the next day? This one is what bugs me the most. 

 

The outcome of this should lead me to a better understanding of the car's ignition system, so I'll call that my silver lining. 

 

 

Edited by cpolyak
typo
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Set your ignition timing back to 32 degrees. No more. No less. See if that helps. You can easily test your distributor with an adjustable timing light. The 123 set-up is super cool, but not everybody has $500 to throw at it. 

 

Why you'd advance timing in altitude makes no sense to me. If anything, I'd consider *perhaps* adjusting fuel mixture via the "verboten screw" and throttle plate to pump synchronization variations. Kugelfischer pumps are matched to the factory distributor / ignition advance curve. When you up the full advance, it changes the entire range of ignition timing. 

 

I believe your car should have the "008" mechanical advance distributor (replaced by a nearly identically curved "002" distributor per Bosch in the mid 1980s.) That might be the source of some of your issues. is there a vacuum canister on the side of your distributor now? There shouldn't be. 

 

Curious to see how this unfolds and what solves the issue. 

Edited by wegweiser
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7 minutes ago, wegweiser said:

Set your ignition timing back to 32 degrees. No more. No less. See if that helps. You can easily test your distributor with an adjustable timing light. The 123 set-up is super cool, but not everybody has $500 to throw at it. 

 

Why you'd advance timing in altitude makes no sense to me. If anything, I'd consider *perhaps* adjusting fuel mixture via the "verboten screw" and throttle plate to pump synchronization variations. Kugelfischer pumps are matched to the factory distributor / ignition advance curve. When you up the full advance, it changes the entire range of ignition timing. 

 

I believe your car should have the "008" mechanical advance distributor (replaced by a nearly identically curved "002" distributor per Bosch in the mid 1980s.) That might be the source of some of your issues. is there a vacuum canister on the side of your distributor now? There shouldn't be. 

 

Curious to see how this unfolds and what solves the issue. 

The car has the 013 distributor, which as I understand it, was factory installed for 74tii's. My 73 was at very tail end of that model year production, so I believe the 013 may be correct. Yes, it has vacuum canister but it's now disconnected as the pertronix shouldn't require it. I'll do a little more research and will likely start troubleshooting by retarding advance. 

 

 

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Hrm....... Odd.

 

On 74 tiis - that canister acts as a vacuum RETARD unit, not ADVANCE like most other cars. A petronix only replaces the mechanical action of the points, and has NO EFFECT on ignition timing - so if your car did indeed have the "013", the vacuum should be properly hooked up to affect dynamic ignition timing, regardless of the method spark is triggered. I suspect your distributor has been swapped at some point. After 40+ years, who knows, right? Indeed your VIN (2764445) is a super late 73 though. 

 

 

Edited by wegweiser
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7 minutes ago, wegweiser said:

Hrm....... Odd.

 

On 74 tiis - that canister acts as a vacuum RETARD unit, not ADVANCE like most other cars. A petronix only replaces the mechanical action of the points, and has NO EFFECT on ignition timing - so if your car did indeed have the "013", the vacuum should be properly hooked up to affect dynamic ignition timing, regardless of the method spark is triggered. I suspect your distributor has been swapped at some point. After 40+ years, who knows, right? Indeed your VIN (2764445) is a super late 73 though. 

 

 

Paul,

I misspoke - the vacuum retard line is properly connected to the distributor. Yeah, 40+ years later, hard to tell what's original and what's not. Thanks for your comments. 

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I know when I drove my flat-lander sea level dwelling tii across CO and the mountains of CA last summer, I definitely lost power. Not enough to change any tuning settings for a day or two of driving, but it was a drag. Keep in mind also - if you're not able to get RELIABLE 93 octane fuel, you need to be SUPER vigilant about avoiding too much advance - especially in a tii. That can cook / melt your pistons and nobody wants to go to THAT party. I actually set my timing back to about 30 degrees, when 93 Octane became scarce, en route, as I feared lean/ detonation issues with 89 / 91 fuels. (I'm running 10:1 pistons and am admittedly a tad paranoid.)

 

if you have access to the original repair manual (or the owners manual, even!) graph your distributors advance curve with an adjustable timing light and compare it with the optimum factory curve. You'll soon know if the advance mechanism / distributor is functioning properly. Although I don't trust their pre-installed petronix style stuff, the Ireland distributor is dead nuts perfect at mimicking the "008" original advance curve of a tii. For the money, it's a decent option.

 

I hug my points at every valve adjustment / 8000 miles. 

Edited by wegweiser
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It certainly sounds like too much advance. The atomisation of the fuel by the Kugelfischer injection is so good it doesn't require the compensation of an early spark compared to the big gobs of fuel coming from a carb. Flame travels very quickly through the tii charge. 

 

The factory tii ran about 28 degrees max BTDC from memory. 38 is a huge bump on this. Check the advance curve you have by plotting the curve every 500 rpm with your adjustable timing light. At the very least check that your ignition can be seen advancing and retarding when the engine is revved.Your earlier drive may not have been quite as spirited and may not have seen such a load on the engine at higher revs. It's amazing how much 'normal' driving barely gets the engine moving / on cam. If you had a 32/36 you may not even get the secondary open. 

Edited by Simeon
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After some troubleshooting this morning, retarding advance didn't make much of a difference.  Still starts right up cold or warm, but under any acceleration there is consistent moderate/severe stumbling as the engine just doesn't seem to want to put out power or rev.

 

I went through fuel supply system and it checked out great. Clean filters, return quantity within parameters given by McCarthy book. Spark plugs are pretty black/sooty which makes me think the issue might be AF ratio.

 

So, I pulled out the NGK BP5ES plugs which only had 500 miles on them, and threw in my spare set of BP6ES plugs. Car now runs like a top. So the stumbling/missing was the result of fouled plugs - but why they are fouled is bugging me. This points back to the AF ratio - too rich?

 

The attached photo is new plugs, after 8-10 miles of driving, the last few miles hard once engine was warmed up.  I don't know much about plug health, but I do see a coating of soot forming at the plug base. The car was originally tuned at sea level, and now I'm in Denver, which would lead to a richer ratio. 

 

 

 

IMG_0731.JPG

Edited by cpolyak
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4 minutes ago, Simeon said:

Interesting. I think the 6's are actually a cooler running plug than the 5's

 

Correct, but they're all I had on hand. Ordered another set of 6's, and hoping to get AF meter on car to figure out how rich she's running. 

 

 

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Conclusion: car had idle AF ratio of 10:1 - very rich which explains why the plugs fouled. Leaned it to 13.5:1. Replaced 013 distributor w/ IE tii distributor. Set plug gap .033 and set timing to 37* at full advance. In the end, I don't think the ignition work had anything to do with the issue - it was coincidental that the plugs gave up the ghost right after the points were pulled. 


Car now runs terrific, strong/steady power through all RPM ranges. Temp gauge stable at 1/3 to just below 1/2. Better fuel economy too! 

 

I recognize that the IE instructions, and the blue book, call for max advance 32-34, but the extra few degrees really help the engine run better. Blue book specs are for sea level. My understanding is that at high altitudes such as Denver where I am at 5500', thinner air results in less compression pressure which leads to fuel/air mixture burning slightly slower. Advancing timing a bit compensates for this. I've seen different rules of thumb discussed online of anywhere from 1/2 degree to 1 degree advance per 1000'. 

 

Thanks all for the suggestions. 

 

 

Edited by cpolyak
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