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Old 06-13-2021, 07:08 PM
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Default Distributor weight questions

Looking for a little distributor education today.

I've got a couple used distributors in a box and was going through them. I also removed the distributor out of my car to add a limiting bushing to shorten the timing curve. I noticed the weights on my operational distributor are different than my parts distributors. What effect of timing does this have if any? The weights out of my parts dizzy have a number 37 stamped into them whereas the operational weights have no number.

The cleaner looking weight is out of my operational distributor vs the brown one from my parts distributor.
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Old 06-13-2021, 07:29 PM
Sun Tuned Sun Tuned is offline
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Well the 37’s will shorten it all right. Usually some 5 degrees on the later distributors..

Some of 67/68 distributors used those 37 weights and they had a differently shaped cam they used em on. Then I saw them again some years later where I think they wanted to shorten some later model distributors.

They work fine but they will be rather limited on a later model fatter cam distributor shaft.

Check your work when done!

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Old 06-13-2021, 07:38 PM
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There was currently no limit bushing installed on my distributor, I have a brass bushing from a Mr gasket kit I bought years ago and was planning on installing that. Was hoping to cut 2-3 degrees out of the curve??

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Old 06-13-2021, 09:54 PM
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About the only thing you can do is try the little bushing and see. Won’t cost anything but sone time. Then if you’re not where you need to be then you’re going to have to go all watchmaker on it.

That means braze up the hole in the plate or mig it whichever you prefer. Then chainsaw file it out EXACTLY where you want it.

There’s about 10 different ways to do that but at the end of the day those are going to be your best options, if you’re searching for an exact number.

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Old 06-13-2021, 09:57 PM
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I had the distributor sent out to be rebuilt and setup a couple years ago. It's currently got 20 degrees mechanical advance. All in around 25-2600rpm. It appears the slot has been shortened already. My goal is around 16-18 degrees mechanical. Hoping the bushing gets me there.

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Old 06-13-2021, 10:02 PM
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Always thought a Pontiac liked 6-8 initial and 34-38 depending on a Whole Bunch of things. 20 mechanical does not sound like enough.
plus about 12 vacuum.

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Old 06-14-2021, 03:42 AM
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If your heads are the old Edelbrock aluminum heads you will probably be wanting up to 41 degrees of total timing while the new Eddy's like around 34°.

So new Edelbrock heads would be 20° mechanical and 14° initial and you will be right where you want to be.

If you have old Edelbrock heads and you have 20° mechanical you would need 21° initial and that will cause problems on hot starts. Probably end up lengthening the mechanical curve up to 26° to 28° to keep the engine from fighting you after a hot soak.

Padgett, Pontiac iron heads do like up to 38° and the consensus is up to but not exceeding 16° initial, and being from a very warm area in the Summer (only 60 miles to Palm Springs) I'll usually not exceed 14° initial which will leave 24° mechanical advance. Also the vacuum advance mentioned is in the ball park where limiting vacuum advance to 12 to 14 degrees seems to work well.

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Old 06-14-2021, 06:18 AM
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Quote:
Originally Posted by lust4speed View Post
If your heads are the old Edelbrock aluminum heads you will probably be wanting up to 41 degrees of total timing while the new Eddy's like around 34°.

So new Edelbrock heads would be 20° mechanical and 14° initial and you will be right where you want to be.

If you have old Edelbrock heads and you have 20° mechanical you would need 21° initial and that will cause problems on hot starts. Probably end up lengthening the mechanical curve up to 26° to 28° to keep the engine from fighting you after a hot soak.

Padgett, Pontiac iron heads do like up to 38° and the consensus is up to but not exceeding 16° initial, and being from a very warm area in the Summer (only 60 miles to Palm Springs) I'll usually not exceed 14° initial which will leave 24° mechanical advance. Also the vacuum advance mentioned is in the ball park where limiting vacuum advance to 12 to 14 degrees seems to work well.

My heads are the new design edelbrock heads. When talking to butler they recommended 16-18 degrees initial based on my engine combo and 32-34 total.

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Old 06-14-2021, 07:13 AM
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The lead time needed for any type of chamber is heavily influenced by how fast your cylinder pressure rises due to many factors that make up the overall way that happens!

I would go by what Butler has said as a real good starting point / well in the ball park range!

If you drill out and tap the breaker plate for a 8/ 32 machine screw near the end of the slot you can double nut it ( top and bottom of the plate) but grind the bottom nut off into a Cam shape, then you can move the timing limit back & forth by some 4 degree's

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Last edited by steve25; 06-14-2021 at 07:19 AM.
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Old 06-14-2021, 08:56 AM
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I'd leave it as-is and test it.

With a 20 degree curve you'll be 12 or 14 to get 32 or 34. If the engine decides that it needs more initial timing to idle well and does NOT "buck" the starter on a restart when it's fully heat soaked then you can shorten things up a bit if/as needed.

Also keep in mind here that you are taking advice from folks who don't like, want, or ever use vacuum advance in these engines. Not going to get into any towel hanging or pissing contests there, but ALL of these engines benefit from some additional timing at light load, some like some at idle, and for sure it will NOT have that timing simply because you are using heavier weights and lighter springs to try to get it "all-in" earlier in the RPM range........FWIW........Cliff

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Old 06-14-2021, 07:38 PM
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The timing slot has been filled previously to achieve 20 mechanical without a bushing. Adding the bushing took out nearly 6 degrees of movement. I pulled the distributor back out and tomorrow will disassemble it and file the slot a little bit. Looking to add about 2 more degrees.

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Old 06-15-2021, 06:10 PM
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So I filed out the slot and achieved an additional 2 degrees of mechanical advance. It seems my weight/spring combo is very inconsistent though. When cold the timing is coming in around 25-2600rpm. When warm it's all in by 2000-2100 which seems too soon. Even with the stiffest springs from the Mr gasket set I have on the shelf the timing is still coming in around 2000rpm. Could anybody recommend a source for better springs for the distributor?

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Old 06-15-2021, 06:47 PM
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You need to pull the Dizzy out of the motor, remove the gear and pull out the advance shaft, clean out its bore and relube it with wheel synthetic bearing grease.

There should be no difference between cold and hot
timing.
The difference is due to dried up old lube holding back on the motion of that shaft when cold!

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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
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Old 06-15-2021, 06:54 PM
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Quote:
Originally Posted by steve25 View Post
You need to pull the Dizzy out of the motor, remove the gear and pull out the advance shaft, clean out its bore and relube it with wheel synthetic bearing grease.

There should be no difference between cold and hot
timing.
The difference is due to dried up old lube holding back on the motion of that shaft when cold!
I just had it apart and relubed it yesterday. I can assure you there is no hangup in the advance shaft.

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Old 06-15-2021, 07:04 PM
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Agree sounds like weak springs. Should be all in around 3200-3400. and 34-38 degrees. Do you have a timing light with a dial ?

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Old 06-15-2021, 07:17 PM
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Just covering all bases!

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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
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Old 06-15-2021, 07:24 PM
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Quote:
Originally Posted by padgett View Post
Agree sounds like weak springs. Should be all in around 3200-3400. and 34-38 degrees. Do you have a timing light with a dial ?
I've been told 32-34 total with my cnc chambered edelbrock heads, I'm at 32 total right now. My timing light is fixed but my balancer is marked up to 50 degrees. I'm also thinking weak springs, just want a better source for them!

Quote:
Originally Posted by steve25 View Post
Just covering all bases!
Fair enough, you never know the condition of the parts on these cars; they're getting older everyday!

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Old 06-15-2021, 07:56 PM
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Sawbuck and a fin.

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Old 06-15-2021, 09:30 PM
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Where off-the-shelf aftermarket is concerned, I’ve had good results with the medium and heavy tension springs from the Moroso recurve kits.

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Old 06-15-2021, 09:39 PM
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Quote:
Originally Posted by Rocky Rotella View Post
Where off-the-shelf aftermarket is concerned, I’ve had good results with the medium and heavy tension springs from the Moroso recurve kits.
Would I be better off with my existing weights or the moroso weights if I use their springs?

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