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#1
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Where to Find Distributor Springs and Weights?
I want to try and put my points distributor (112008) close to original timing.
The last time I tried to get it running, idle timing was erratic and I want to eliminate the distributor as a possible source. I just replaced the 50-yr-old harmonic balancer as another possible contributor. What are the stock weights or where can I look that up? Seems the info is available for HEI but I haven't found a reference for points distributor parts. Is there anyone that sells used originals? I even tried buying a used distributor off eBay and the weights were not stamped with codes so I don't trust they are original. I attached some info I have about the stock timing and what I believe is the current setup with Crane springs. I want to make sure the mechanical advance does not kick in at idle and I don't trust these old measurements. I think they were guesses captured with the engine running and a sketchy tach reading. Maybe it's OK but I'd feel better knowing... Mike |
#2
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If your timing is unstable with the stock heavy springs , or even with medium aftermarket springs you should first confirm that the advance shaft is not hanging up due to old harden factory lube.
Here's the overall timing curve from a typical high comp era 4 bbl motor. Your chart and this chart should only be used as ball park due to today's fuel .
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I do stuff for reasons. Last edited by 25stevem; 02-06-2023 at 12:43 PM. |
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#3
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I really don't know if the timing is still unstable but want to do what I can to eliminate possible causes for the bad history. It has been 4 years since I last tried to get it running and there were multiple issues. If the Crane silver and blue springs are known to hold zero mechanical up to 800 or 900 rpm, then I guess I'm good? |
#4
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25stevem -
I'm looking at the chart you shared and don't get it. It shows 20 mechanical and 20 vacuum at 3000 rpm but the total is 50 ??? But it does show 0 mechanical at 1000 rpm. Is this typical for a stock distributor? If so, I definitely need stronger springs. I may have the originals from the used disty, but still hoping someone can help with the weight ID and source. Thanks again Mike |
#5
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#6
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The OEM timing is compromised so that a bad tank of gas combined with carboned-up chambers from Grandma driving and lack of maintenance wouldn't pop the engine. You're almost certainly more maintenance-intensive that run-of-the-mill drivers from fifty years ago. Give that engine the timing it wants, instead of the timing GM cursed it with. |
#7
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
#8
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Dont sweat that chart. Give it as much timing as it will take up to 36°, without pinging, hook up your vacuum advance and go. If its at 10° or even 15-20° at idle the only adverse effect would be improved idle cooling. If you have heavy weights on the distributor and the distributor is good, not loose on it bushings and wobbling, and the timing is still erratic at idle, it may be a well worn cam gear. Old worn distributor drive gears will cut a cam and the slop is visible with a timing light. A new gear on the bottom of that rebuilt distributor would take up most of the slop. And, the slop left usually wont be noticed behind the wheel. Most all Pontiac distributor weights and center plate combos come in at 24°-25° leaving you at 10°-11° at idle. If you use Chevy weights run them upside down to be correct. Dont sweat it if its a little higher at idle. You want to be correct all in. It wont hurt anything at all. What hurts more than anything, is sitting motionless.
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#9
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Got it, thank you. |
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#11
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Good info on the worn gear. I'll check it. My impression was some aftermarket springs and weights could cause erratic idle timing by allowing mechanical advance to cut in and out, or allow the weights to "rattle" right at idle rpm. Is this inaccurate? As to the overall curve, I set it up for 31 to 34 total mechanical (base + advance) but I want to remove the springs and weights as a possible contributor to the idle issues I had when I last had the engine running. My troubles were likely more about the carb but I do remember the timing jumping around when fighting to get the carb to run on its idle circuit. I can install stronger aftermarket springs as a starting point to reduce the risk of erratic idle timing being a factor. I just think it would be safer to start with stock springs and weights so still hoping for guidance and a source. Mike |
#12
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This thread reminds me, I cant tell you how many project cars I've bought where the previous owner couldn't get it to run right. Putting a timing light on them showed timing jumping around like crazy. They all had the vac advance hooked into manifold vacuum, so the distributor was sitting there just swinging the timing around like crazy at idle. Switched it to ported, and the timing was smooth and steady.
Not saying that's your issue. Just reminded me on how something so simple can often be overlooked.
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"Those poor souls have made the fatal mistake of surrounding us. Now we can fire in any direction" 1970 Trans Am RAIII 4 speed 1971 Trans Am 5.3 LM7 1977 Trans Am W72 Y82 1987 Grand National |
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#13
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#14
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Unlike HEI, GM only used a handful of different weights for points distributors. The center cam (which is welded to the main shaft) and springs controlled the rate. The limiting pin and its corresponding slot in the breaker cam assembly largely limited total timing.
The most effective solution is to get it on a distributor machine and accurately verify the advance curve at idle and throughout the entire RPM range. Then you can eliminate the distributor as a variable. If you happen to be anywhere near Omaha in the future, you're welcome to stop by and we'll throw it on my machine. |
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#15
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1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#16
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post a picture if your weights it will be easy to tell if you have aftermarket ones or not
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If your not at the table you're on the menu A man who falls for everything stands for nothing. |
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#17
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Wasn't 68 like the first year of ported vacuum?
It's what I use and again ... perfectly steady vacuum signal and timing.
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#18
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https://forums.maxperformanceinc.com...r.php?u=143447
FWIW, this is a member on the board that does distributor service, he's located in Memphis TN. Many people on the board have been happy sending their distributors to him to have them curved, and repaired. I'm certain he has parts from old distributors that he could sell you also, along with springs and weights. I've spoken to him on the phone, and he's a great Pontiac guy. |
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#19
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The comment about ported vs manifold vacuum makes me wonder if the erratic idle timing could all be about my carb and my distributor is fine. The issue was "nozzle drip" and flooding in the past. The carb was never set up and when I tried, I could not get it to idle without cracking the primary blades. Perhaps this caused the vac advance to cause the erratic timing....?? Thanks to you guys, it now makes sense to compare idle timing with and without the vac advance. Doh!! The distributor is only one "unknown"... context is a self-induced mess. You can get a feel for the bigger picture here: http://forums.maxperformanceinc.com/...d.php?t=861753 I've been through the carb again with guidance from Cliff and Kenth, but it's still a big unknown as it is a "Frankencarb" (thread here). It appears "sound" but definitely unproven and still risky. I'm trying to learn, though... The biggest mess was rust in the tank. I am just doing what I can to address "known caca" before trying to get the car running. I installed a new gas tank and fuel pump, a new balancer, and am currently installing a new radiator. The distributor is hopefully last on the list. Hope is a strategy.. Mike |
#20
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Causes for erratic timing at idle speed is most often due to too weak centrifugal timing springs and/or a vacuum advance connected to manifold with a too weak vacuum signal to fully employ the vacuum advance unit. Move to ported source.
Set the timing at idle speed with the original springs removed from the centrifual advance. Note: Look for/mount a 1/4" bushing on centrifugal stop pin, need to be there. Use a dial-back timing light, set 30° for 3.25" mains engines and 32° for 3.00" mains engines. Mount the original springs and check for initial timing, which usually ends up at 9°-12°. If you think your engine needs a faster "all in" curve, replace original springs for weaker springs, but not TOO weak. Look for steady timing mark at idle speed. In any case, you will never exceed the total timing you sat with the springs removed. Now itīs time to tune the carburetor. |
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