Who does dist. recurving near L.A?

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sc2dave
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Re: Who does dist. recurving near L.A?

Post by sc2dave » Thu Mar 08, 2018 11:36 pm

Just remembered that I have an old Corvette points dist. laying around. i can use those weights if I need to.

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Re: Who does dist. recurving near L.A?

Post by Tuner » Fri Mar 09, 2018 1:28 am

sc2dave wrote:
Sun Mar 04, 2018 11:21 pm
Here it is. The weight pins are in excellent condition.
Image

Unless you can find original weights and bushings I think you're stuck with the advance curve kit weights because the pivot pins are the small .151" diameter that use a plastic bushing and the advance curve kit weights have a larger hole (OD of the bushing) than OE weights. The kit weight ID and bushing OD is different size (larger) than the OE weights.

The points distributor weights and pivot pins are approximately 1875" (3/16"). The points distributor weight lever is shorter than the HEI and the angle between the lever and the weight (on opposite sides of the pin) is not the same.

I found a 400 cam and I am going to do an HEI tomorrow or Monday so I can rig it up with the 400 cam and the weights you have (I think there is a pair in the bone pile) and see what springs will make a functional curve and give you the spring specs. I'll try it with the springs that come in the MSD kits because they are the more likely ones you can find. The top spring in the picture looks like the MSD "light silver" spring so you may have the other to make a pair??? Whatever springs you use should be an identical pair.

Would you post a picture with the springs removed and the mechanism in the full retard position, with the weights as close back against the cam as they go in full retarded position. In other words, as close as the spring tension can pull the pins together. I need to see how the tip of the 400 cam and the lever near the pivot pin are contacting each other to make sure I use the same weights as your have.

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Re: Who does dist. recurving near L.A?

Post by sc2dave » Fri Mar 09, 2018 8:09 pm

Here it is.
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Re: Who does dist. recurving near L.A?

Post by MadBill » Fri Mar 09, 2018 9:20 pm

Tuner wrote:
Fri Mar 09, 2018 1:28 am
...Whatever springs you use should be an identical pair...
Some advance kits chart the curves with both matched and unmatched springs. What can go wrong? The overall spring tension will always be the average of the two :-k
http://www.hotrod.com/articles/hppp-130 ... ce-curves/
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

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Re: Who does dist. recurving near L.A?

Post by sc2dave » Sun Mar 11, 2018 11:22 pm

Tuner wrote:
Fri Mar 09, 2018 1:28 am




I found a 400 cam and I am going to do an HEI tomorrow or Monday so I can rig it up with the 400 cam and the weights you have (I think there is a pair in the bone pile) and see what springs will make a functional curve and give you the spring specs. I'll try it with the springs that come in the MSD kits because they are the more likely ones you can find.

you ever get to this?

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Re: Who does dist. recurving near L.A?

Post by Tuner » Tue Mar 13, 2018 7:28 pm

sc2dave wrote:
Sun Mar 11, 2018 11:22 pm
Tuner wrote:
Fri Mar 09, 2018 1:28 am

I found a 400 cam and I am going to do an HEI tomorrow or Monday so I can rig it up with the 400 cam and the weights you have (I think there is a pair in the bone pile) and see what springs will make a functional curve and give you the spring specs. I'll try it with the springs that come in the MSD kits because they are the more likely ones you can find.
you ever get to this?
Sorry about the delay.

I am cleaning and fluffing and buffing the HEI parts today and need to replace a bushing so there should be info for you this evening or tomorrow. I got invited to go flying Saturday so the distributor waited until today.

In this picture
Image

It looks like the weight on the left has a bump in the intersection of the lever and the weight arm near the pivot pin that has been removed from the weight on the right (nearest the number 400 on the cam). That bump needs to be removed from both weights and the face of the lever which contacts the side of the weight needs to be flat and straight and extend beyond the contact point with the cam, so the flat plane of the lever can roll smoothly on the cam with no abrupt change of angle. The lever is a cam follower somewhat like a solid or hydraulic (flat) lifter in an engine and needs to be a flat plane on the surface that contacts the cam. Fortunately, the curve kit weights are soft material so you can do this with a file. The factory Delco weights are so hard they will kill a file.

Are you using the vacuum advance? If so, measure the distance between the diaphragm rod where it connects to the pickup lever and the end of the slot. Measure the travel of the rod, and if you can, use a vacuum gauge and a hand vacuum pump or just suck on it, measure the vacuum amount when it starts to move and when it contacts the end of the slot at maximum vacuum advance.

The HEI is on the front burner today so there should be some information for you this evening or tomorrow.

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Re: Who does dist. recurving near L.A?

Post by Tuner » Sun Mar 18, 2018 4:32 pm

Sorry about the delay. I won't bore youall with the details of the right knee issue, I'll just say be careful what you choose to stand on when you pull the distributor out of a sorta tall 4WD Bronco.

OK, here is the deal with a HEI using a 400 cam and advance curve kit weights that look like those in the pictures above.

First, the weights I used have the little bump in the lever close to the pivot but it didn't interfere with the situation, at least in the case of the unit I used in the distributor machine. However, be advised that due to manufacturing tolerance not all HEI distributors are exactly alike, they can differ by several thousandths, so if the bumps interfere in your case, they should be filed down so just the flat plane of the lever is in contact with the 400 cam.

With a #400 cam, a pair of blue MSD springs gave the following curve, in crank degrees and crank RPM.

800 …. 0° + 18° initial .. 18°
1000 .. 2° … ^^^ .. 20°
2000 .. 8° 26°
2500 .. 12° 30°
3000 .. 14° 32°
3500 .. 15° 33°

If you need more or less total, adjust initial as necessary.


The blue MSD springs I have here are .028” wire diameter, .250 coil diameter, and .605” inside the loops (free length, not stretched). The installed length of the springs (the span between the outside of the pins) in this HEI I used is .695”, so the spring preload is .090”.

The important thing is the two springs must be preloaded the same amount so the tension they have is identical. With Delco type advance mechanism this is important to eliminate friction so the retard RPM will be close to the same as the advance RPM. If the springs have lopsided tension the RPM may need to drop several hundred for the mechanism to retard. At idle, needing to be below 500 RPM to fully retard when the advance starts at 1200 is aggravating when you are trying to set the initial.

In the case of this #400 advance cam and these curve kit weights it is particularly important the springs be installed with identical tension because in the fully retarded position the springs and pins are lined up almost 180° straight across the center of the main shaft, so have no angle offset which provides leverage at low RPM to pull toward retard. This less than ideal spring angle situation can make it difficult to set the timing and cause erratic idle speed because the timing may not be the same every time the engine returns to idle.

If the pins are different length apart, one pair for one spring is .695” and the other pair for the other spring is .705” (for example) then in that case set the free length of the springs so one is .010° longer than the other, bend the spring eyes to set the length.

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Re: Who does dist. recurving near L.A?

Post by Tuner » Sun Mar 25, 2018 4:32 pm

Well, how did it go? Were you able to find the MSD springs?

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Re: Who does dist. recurving near L.A?

Post by sc2dave » Sun Mar 25, 2018 6:16 pm

Sorry for the delay. Ive been working 7 days a week.No, it's been years since I've installed them. I might have to order more.

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Re: Who does dist. recurving near L.A?

Post by sc2dave » Wed Apr 18, 2018 8:11 pm

I finally got around to ordering an adv curve kit. I set initial at 12*, with vac. disconnected, with Gold springs I got 25*. Idle was around 750.I think those 2 were 37* After checking this, I went ahead and hooked up vac adv to ported. Drove it around a bit and it picked up a good amount of power. Now, how do i adjust vac adv. now?

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Re: Who does dist. recurving near L.A?

Post by Tuner » Sat Apr 21, 2018 1:12 pm

sc2dave wrote:
Wed Apr 18, 2018 8:11 pm
I finally got around to ordering an adv curve kit. I set initial at 12*, with vac. disconnected, with Gold springs I got 25*. Idle was around 750.I think those 2 were 37* After checking this, I went ahead and hooked up vac adv to ported. Drove it around a bit and it picked up a good amount of power. Now, how do i adjust vac adv. now?
If your vacuum advance is adjustable it is done with 1/8" or smaller hex key (allen wrench) in the through the hose nipple. Counter-clockwise for less advance and clockwise for more. Unfortunately, not all adjustable vacuum advance units are created equal, some have a poor choice of spring in them and can't be adjusted to give the desired advance degrees vs. inches Hg vacuum.

It should start to move at about 6" vacuum and reach full travel at about 15" and move about .180" ~ .200".

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Re: Who does dist. recurving near L.A?

Post by 1972ho » Sat Apr 21, 2018 5:00 pm

If you are still looking for someone to curve that distributor and want to drive to upland Dave Lang at fuel curve west has one of those distributor machines and can curve it for you.

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Re: Who does dist. recurving near L.A?

Post by sc2dave » Tue May 01, 2018 7:07 pm

1972ho wrote:
Sat Apr 21, 2018 5:00 pm
If you are still looking for someone to curve that distributor and want to drive to upland Dave Lang at fuel curve west has one of those distributor machines and can curve it for you.
How much? Probably same as all the others?

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Re: Who does dist. recurving near L.A?

Post by sc2dave » Tue May 01, 2018 7:09 pm

Tuner wrote:
Sat Apr 21, 2018 1:12 pm
sc2dave wrote:
Wed Apr 18, 2018 8:11 pm
I finally got around to ordering an adv curve kit. I set initial at 12*, with vac. disconnected, with Gold springs I got 25*. Idle was around 750.I think those 2 were 37* After checking this, I went ahead and hooked up vac adv to ported. Drove it around a bit and it picked up a good amount of power. Now, how do i adjust vac adv. now?
If your vacuum advance is adjustable it is done with 1/8" or smaller hex key (allen wrench) in the through the hose nipple. Counter-clockwise for less advance and clockwise for more. Unfortunately, not all adjustable vacuum advance units are created equal, some have a poor choice of spring in them and can't be adjusted to give the desired advance degrees vs. inches Hg vacuum.

It should start to move at about 6" vacuum and reach full travel at about 15" and move about .180" ~ .200".
so should I crank up the vac adv as much as possible w/o it pinging?

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Re: Who does dist. recurving near L.A?

Post by sc2dave » Sat Sep 15, 2018 7:18 pm

So yes?

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