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I am probably not doing this right so hopefully someone can straighten me out. "78 with L82 and 4 speed. Elgin 224/234 465/485 cam. Idle at 900 RPM. Carb rebuilt by Lars. Distributor is a stock HEI. I'm checking the timing using Lars Tech Bulletin Rev y 1-2-15.
With the Vacuum off (and plugged) I am reading 16 degrees at idle. With the Vacuum connected, I read 32 Degrees which means I have a total vacuum advance of 17 degrees. Correct?
With the vacuum off and using the short springs shown in the picture below, I get 36 degrees at about 2,000 RPM. last night I had a helper and was able to verify the 2,000 RPM. Today I am by myself and I am only going by the sound. I am certain I get full advance well before 2,800 RPM.
I tried a different set of springs, the silver ones that are installed in the picture. I don't see any difference. Still pegs out at about 2K.
These are springs I got with a NAP kit. I am using the original weights.
Am I good to go or do I need different springs?
Also note that the posts that the weights pivot on have a lot play in them. The kit included poly bushings which fit the weights that came with the kit but the inside diameter of the bushing is the same as the original weights. Do I have an issue here too?
Thanks in advance for any help anyone is able to offer.
Those are some heavy springs.......they should not come in that early but close inspection of your photo shows you have no bushings in it at all and this is going to cause things to go wonky.
Get the old classic Mr. Gasket curve kit....it comes with a little piece of paper that has the different curves for the springs.....
There never were any bushings with the original weights. Mybe they disintegrated over the years or? Anyway, The kit I got from NAPA is very similar to the Mr Gasket except for maybe the springs. I will try AutoZone or o'Reily's and see if they have Mr Gasket. For now I installed the NAPA weights along with their bushings and the silver springs. No change.
I don't have anything to judge by but if you say those are heavy springs I believe you (I'm familiar with your expertise on this forum). I would expect that the heavy springs would give me the exact opposite - full 36 degrees at a much higher RPM.
I think I'm doing this right: I have my Craftsman dial set at 36, the vacuum advance is off and I move the throttle. Watching the balancer, I get the mark hovering under the 0 degree mark at about 2,000 RPM. I guess you could question the accuracy of my tach. For now I can say that it tachs about 3,500 RPM at 70 MPH IIRC with P255 R60 tires and 3.72 rear end.
There never were any bushings with the original weights. Mybe they disintegrated over the years or? Anyway, The kit I got from NAPA is very similar to the Mr Gasket except for maybe the springs. I will try AutoZone or o'Reily's and see if they have Mr Gasket. For now I installed the NAPA weights along with their bushings and the silver springs. No change.
I don't have anything to judge by but if you say those are heavy springs I believe you (I'm familiar with your expertise on this forum). I would expect that the heavy springs would give me the exact opposite - full 36 degrees at a much higher RPM.
I think I'm doing this right: I have my Craftsman dial set at 36, the vacuum advance is off and I move the throttle. Watching the balancer, I get the mark hovering under the 0 degree mark at about 2,000 RPM. I guess you could question the accuracy of my tach. For now I can say that it tachs about 3,500 RPM at 70 MPH IIRC with P255 R60 tires and 3.72 rear end.
New NAPA weights with nylon bushings installed
Now the above picture has a much weaker spring pack on it......try a heavy and a light together and see if it changes in your favor....you can do a heavy and a light as the weights are linked....also....put some kind of grease on the bushings and rest pads.....not much though!
I'm checking the timing using Lars Tech Bulletin Rev y 1-2-15.
E-mail me for the current info - that's an obsolete document you're working to. Other than that, you're doing it right - install some stiffer springs as Jebby stated above.
I never had much luck with the after market weight set either. Even with the heaviest springs it came it too early. It seemed to me that where the weight acts upon the center plate is wrong creating a fulcrum with too much leverage regardless of the stiffness of the spring.
One thing you can try is to lighten the aftermarket weights. They're cheap and easy to come by so whats to lose. Just grind some of the metal away on the fat side of the weight. This will create less centrifugal force acting on the springs and change when the full advance comes in.
I also tried flipping the center plate but that didn't really change when it came in so much as how much advance it achieved.
Ultimately the advance (how much) achieved is governed by the center plate shape, and when advance is achieved by the springs and the shape combined. The smaller tip flats contact the center plate and stop the movement of the weights so this is the ultimate limit. Unless the RPM's and /or enough centrifugal force is generated by the weights to allow the tips to leverage up enough to cause the springs to stretch a little more and allow the flats to kind of rise up further advancing the timing.
I tried many combos with my HEI and was not really satisfied with any of the results I got stock or aftermarket or a combo of the two.
Finally decided to make my own center plate using the stock one as a model but modifying mine a little to get a positive stop and the rate of advance I wanted. Case hardened it to prevent wear and now that is what I am running with the stock weights.
In any case try using the aftermarket center plate with the aftermarket weights or aftermarket center plate with stock weights to see what you come up with. Then if still not satisfactory nothing to lose by modifying the aftermarket kit to your liking.
The bushings on the stock weights are important to the rotation of the weights and how they act upon the center plate though. So getting something to replace those bushings would be a priority if you want to use them.
Just a little worthless info here: Neither Mr Gasket kits received very good reviews.
Those that purchased 927-G said the springs were too long.
Those that purchased 929-G said the bushings were too tall.
Both Mr. G. kits are around $10.
Better quality kits run $25-$30. You know the old saying . . . .
I tried the 929-G yrs ago. I do recall the bushings were a little wonky. Maybe that is throwing your timing for a curve. Pun intended.
Also note how the weights are pictured above. Heavy tail curves to left in one photo but is flipped over in the other photo. Which way is correct? H-m-m-m-m-m-m
If you wanna slog through some of these posts from other forums you can learn a bit about the weights and center plate relationships and their effects on timing.
I finally have been able to get back to my timing issue. Thanks all for the advice. I acquired a SUN Analyzer so I am now able to read the RPMS while adjusting the timing.
Interesting idea REVALATOR! I ground off some of the weights and that works! The weights now scale in at .6 oz on a mail scale. As you can see in the picture the weights are quite a bit smaller now. I checked the initial timing and it comes in at just over 16 degrees. As I rev up the engine I peg out at 36 degrees at 2900 RPM. So I am in line with everything I have been told and read. Will test drive and see how it runs.
But I notice that I get no centrifugal advance until about 2400 RPM. Is this normal? These weights are about half the weight and size of the original ones and makes me wonder if I really have it dialed in the way it should be.
Second questions is why would this distributor need heavy springs and lighter weights when everything I read said you probably need lighter springs to get to full advance at <3,000 RPMS.
Looking at your photo again and a closer inspection in post #1 (top of this page) I noticed code letters on the module. It appears the letters are G and W. Note that the wire colors are Gold and White. Now look again at the orientation.
H-m-m-m-m-m.
Looking at your photo again and a closer inspection in post #1 (top of this page) I noticed code letters on the module. It appears the letters are G and W. Note that the wire colors are Gold and White. Now look again at the orientation.
H-m-m-m-m-m.
WOW! Did not see that, thanks for pointing it out.
if the wires are backwards, would it even work at all?
Looking at your photo again and a closer inspection in post #1 (top of this page) I noticed code letters on the module. It appears the letters are G and W. Note that the wire colors are Gold and White. Now look again at the orientation.
H-m-m-m-m-m.
Thanks for the tip. I opened it up again tonight. The wire that looks gold or maybe orange in the picture Post #1 is really white. Or it was white once upon a time. The wire that looks lighter, maybe white connected to G is actually a green wire. They only plug onto the module one way so I have to determine that the wiring is correct. The car runs and I don't think it would if these were backwards?
So, I'm back to my original question. With stock weights and heavy springs I reach full mechanical advance at about 1800 RPM. Now with very light weights and heavy springs I get full advance at 2900 RPM.
Secondly is it right that I get no mechanical advance at all until about 2000 RPM
FWIW: just recurved an HEI distributor. Used a Moroso 72300 HEI curve kit cost about $14. Only used the weights because the center plate didn’t add enough centrifugal advance. Also used their copper springs..the lightest they offered. On my sun machine got 20 degrees of centrifugal advance @ 2000 Engine RPM. That is with a #370 centerplate and #108 CAM. Different values should provide different results. #375 centerplate provides one of the highest. Was hoping to reuse the OEM 139 weights, but the holes were very worn! With the 20 degrees advance, allows me to set initial advance of a max of 16. Any pinging, lower initial timing.
On the vacuum advance, I limited it to 12 degrees. [/left]
The G & W stand for Green and White. Also the connector is G I proof only goes on one way. One Connector is smaller than the other---won't fit!
Thanks for the tip. I opened it up again tonight. The wire that looks gold or maybe orange in the picture Post #1 is really white. Or it was white once upon a time. The wire that looks lighter, maybe white connected to G is actually a green wire. They only plug onto the module one way so I have to determine that the wiring is correct. The car runs and I don't think it would if these were backwards?
So, I'm back to my original question. With stock weights and heavy springs I reach full mechanical advance at about 1800 RPM. Now with very light weights and heavy springs I get full advance at 2900 RPM.
Secondly is it right that I get no mechanical advance at all until about 2000 RPM
The advance curve should start earlier, your combination of light home made weights and too heavy springs is the problem. You appear to have started with the wrong weight/spring kit based on your early pictures of the weights, post #2.
This stuff is like witch doctor voodoo to me. I can't believe this stuff ever works or worked.
Carburetors, spinning weights and springs, vacuum powered accessories.
It's like watching a Rube Goldberg machine in action or old steam-powered steampunk contraptions. I'm in awe that it works at all and that the people around here have figured out how to control it, but give me digital over analog any day.
I had someone ask me to pay them via Money Order last weekend and my head almost similarly exploded; I paid $10 extra to use PayPal.
So ironic: my dad is afraid of all things digital and refuses to use a computer or smartphone (or even "dumb" cell phone for that matter); I think I have a similar confused fear of analog tech that works "good enough" but doesn't give you feedback or direct, numeric, digital control.
Adam
Last edited by NewbVetteGuy; 04-10-2018 at 01:01 PM.
If the car pings on a test drive, plug the vacuum advance and test drive again. If it doesn't ping now, then leave your initial/mech'l as is and focus on retarding the vacuum advance.
Adam, I remember being in Best Buy one time a few days before Xmas. Their computers went down. I asked if they had a credit card slider machine with the carbon paper receipts. Talk about a 'wtf is that' kinda look!!!
02-24-2018, 01:19 PM
Timing too Early
