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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Check your vac advance at idle which is easier. Your initial is 14* with vac disconnected. Then connect vac advance to manifold vacuum and take your reading. Subtract 14 from that reading and there's your vac advance.
Check your vac advance at idle which is easier. Your initial is 14* with vac disconnected. Then connect vac advance to manifold vacuum and take your reading. Subtract 14 from that reading and there's your vac advance.
all right. new dizzy and changed the can to the napa one (limiting the advance to 10)
no vacuum idle
10 degrees btdc @ 750rpm
33 degrees at 3600 rpm
33-10 equals 23.
with vac connected 28degrees on timing light to get it to zero @800rpm
I thought your new can could only pull 10 degrees of advance.Your numbers show 18 degrees from the new can, which is still too much. Did you not swap over to the NAPA can? Are you getting mechanical advance at idle?
23 degrees of mechanical advance from your HEI dist sounds correct, so that's good.
Why did you change the dist though? You should be all-in at 36 degrees at 3000 RPM. Hopefully the new dist isn't notchy, and you can tweak the springs to get the correct curve.
Last edited by Bikespace; May 8, 2021 at 09:55 PM.
I thought your new can could only pull 10 degrees of advance.Your numbers show 18 degrees from the new can, which is still too much. Did you not swap over to the NAPA can?
23 degrees of mechanical advance from your HEI dist sounds correct, so that's good.
Why did you change the dist though? You should be all-in at 36 degrees at 3000 RPM.
I did swap it. I'm wondering now if it's used or something and they put a different one in the box. The box itself is correct and shows 10-12degrees from the GM spec sheet.
I swapped the dizzy since I was in there and it was new and shiny.
Springs affect mechanical not vac correct? if both then there is the issue. I may have to go back to old dist then change can. Also added the solenoid and it doesn't reach the arm. see pic. I have to adjust that somehow to make it. Holley carb holley arm holley solenoid. I'm going to start making my own stuff and selling it.
last pic shows new can on new dizzy.
Last edited by michael lamoglia; May 8, 2021 at 10:05 PM.
In the next to last photo, your (presumably new, Chinesium distributor) with the clear rotor, there is a hex on the vacuum advance. It is almost certainly adjustable. If you zoom in on the photo in my post #246, you can see the instructions for my Accel adjustable vac can (which also has the hex). I bet you can stick a small hex-head into yours, and adjust the total vacuum advance. Did the new distributor come with any instructions?
Does "211" match what's on the box? Also in post #246, you can see my Mity-Vac. Using one will be a much easier way of measuring the vacuum advance. You might need to limit the vacuum advance by one of the other listed methods (hard stops on the lever arm).
In the next to last photo, your (presumably new, Chinesium distributor) with the clear rotor, there is a hex on the vacuum advance. It is almost certainly adjustable. If you zoom in on the photo in my post #246, you can see the instructions for my Accel adjustable vac can (which also has the hex). I bet you can stick a small hex-head into yours, and adjust the total vacuum advance. Did the new distributor come with any instructions?
Does "211" match what's on the box? Also in post #246, you can see my Mity-Vac. Using one will be a much easier way of measuring the vacuum advance. You might need to limit the vacuum advance by one of the other listed methods (hard stops on the lever arm).
Where's the hex? I see your spec sheet under the mighty vac. What psi am I looking for on my mighty? I'll check if 211 is on the box.
Does "211" match what's on the box?
will check tomorrow
The end of the vac can of both the Accel adjustable have a hex shape, like a 3/4" or something wrench would fit. That is the visual indication that they are adjustable.
The actual adjustment is done with a hex head screw (tiny, like 2, 2.5, or 3mm, or whatever is close in SAE) and that lives inside the can. You remove the vacuum hose, and stick the allen key in through the nipple.
If you have a Mity-Vac, you can also use it to test your vacuum at idle (connected to a manifold vacuum port, or the T on your intake manifold). This is another useful number to know (and to let us know).
Then, you want to make sure that your vacuum can comes into full advance at 2" less than that number. (2 inches of mercury, in hg, is about 1 psi, but psi is usually used for positive pressure, and in hg for vacuum strength).
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
That would be full retard, 0* advance, at 2" i.e. wide open throttle. Full advance of 10-12* should be all in at 8-10" or higher vacuum. Vacuum at idle should be well above this for his engine.
Last edited by resdoggie; May 9, 2021 at 09:06 AM.
Measure your vacuum at idle (you can use the Mity-Vac for that).
Positive pressures (above atmospheric), are measured in psi. Vacuum strength is measured in inches of mercury (Hg).
Say you get 15 in-hg for your idle vacuum reading.
Then use your Mity-Vac to pull vacuum on your vacuum can. Watch where the arm stops moving.
The arm should stop moving (all in, vacuum advance) at 2" less than full idle vacuum.
So for 15 in-hg of idle vacuum, you need to pick a vac can that stops moving at 13 in-hg of vacuum, or before.
As @resdoggie pointed out, if you do this experiment with the Mity-Vac hooked up with your engine idling, you should see that the all-in vacuum gives you 10-12 degrees of total vacuum advance.
Last edited by Bikespace; May 9, 2021 at 09:20 AM.
I am not sure why you think you need a new dizzy.
Your old but GM OEM distrib is of much higher quality than a new $99 Chinese distrib. I would send it back. In this case New (Chinese) is not better than Old (OEM).
You had the old one "dialed in" with a great curve (14/36). Now the new one has a different curve.
Yes you only need to check the vac can at idle. Yours looks to add way more than the desired 10-12 degrees. Use the adjustable one and adjust the hex screw inside. IIRC on those that will limit it, but it may also cause the idle timing to change. If so re-adjust. Using a Mity-Vac may be the easiest way to adjust it.
Measure your vacuum at idle (you can use the Mity-Vac for that).
Positive pressures (above atmospheric), are measured in psi. Vacuum strength is measured in inches of mercury (Hg).
Say you get 15 in-hg for your idle vacuum reading.
Then use your Mity-Vac to pull vacuum on your vacuum can. Watch where the arm stops moving.
The arm should stop moving (all in, vacuum advance) at 2" less than full idle vacuum.
So for 15 in-hg of idle vacuum, you need to pick a vac can that stops moving at 13 in-hg of vacuum, or before.
As @resdoggie pointed out, if you do this experiment with the Mity-Vac hooked up with your engine idling, you should see that the all-in vacuum gives you 10-12 degrees of total vacuum advance.
all cans Napa Chinese and oe stop at the same point in vac gun. I say stop because I stop pumping when lever arm stops advancing forward. See pic a bit less than 15 (13-14) hg. If I pump all the way Kon stop I stop at 27hg.
my hg on my manifold t is 13-14 and bounces around like mad. Vac leak or is it normal. Bounces between 11-13 Vac manifold All the way to see where it stop car off AND on. Napa can on new dizzy I stop pumping when lever stops pulling forward Chinese can seems adjustable but no hex inside that I can see Oe can
The end of the vac can of both the Accel adjustable have a hex shape, like a 3/4" or something wrench would fit. That is the visual indication that they are adjustable.
The actual adjustment is done with a hex head screw (tiny, like 2, 2.5, or 3mm, or whatever is close in SAE) and that lives inside the can. You remove the vacuum hose, and stick the allen key in through the nipple.
it is adjustable. Just tightened it. The lever doesn’t pull down all the way now. So it stops the advance. The pressure on the gun is about the same though. Doesn’t seem to matter as the bar stops earlier. I just answered my own question. Headed to parts store to pickup my accel I had ordered earlier in the week so China can have theirs back.
it is adjustable. Just tightened it. The lever doesn’t pull down all the way now. So it stops the advance. The pressure on the gun is about the same though. Doesn’t seem to matter as the bar stops earlier. I just answered my own question. Headed to parts store to pickup my accel I had ordered earlier in the week so China can have theirs back.
Accel products are often same chinese crap now too fyi just different box and price IMO. Holley bought them out.. Your honestly better off with the old "non shiny" one that worked prior to all this. I have a chinese HEI (tach drive) which hasnt given me any issues but I do hear thats not always the case. If my car had a good working hei distributor when I bought it I would never have swapped it
Last edited by augiedoggy; May 9, 2021 at 12:20 PM.
Accel is same chinese crap now too fyi just different box and price IMO.. Your honestly better off with the old "non shiny" one that worked prior to all this. I have a chinese HEI (tach drive) which hasnt given me any issues but I do hear thats not always the case.
That would be full retard, 0* advance, at 2" i.e. wide open throttle. Full advance of 10-12* should be all in at 8-10" or higher vacuum. Vacuum at idle should be well above this for his engine.
If it's within the proper adjustment range, the screw in the can should be changing the amount of vacuum for it to start moving and the amount needed to get it to travel to the stop.
You should have just bought that hook I posted. It would have fixed it and you'd be done by now. This jumping around with all these different parts is just wasting time and energy.
Put it back together with the stock parts. All you needed was something to limit the travel. A piece of hose over the pin in the slot might have done it. A piece of metal mounted to the arm that blocks part of the slot on the can side so the pin can't move as far. Some people weld it. Some people solder on a brass tab to block the pin. Some people use the MSD hook. Some people mount the Accel 99619-1 limiter plate on the can side of the arm by drilling and tapping a hole and then use it to adjust the travel, mounted like in this post.
At any rate, block the pin from travelling as far and you'll lower the amount of vacuum advance which fixes the problem you have. Less than $10 in parts would have fixed it for you, or you can get creative and make something to add to the stock can for free.
Also, as I previously posted. There was someone else making a limited plate that screws on over the advance arm. I've been thinking about it and I believe it is Lars and Henry Olson who came up with it. Send Lars a nice email explaining that you're having trouble and ask for his information on setting up a HEI distributor. He has an amazing amount of knowledge and what makes him stand out is that he will share that knowledge with anyone who asks nicely. He used to even travel around the country and do tuning days called tuning for beer. He's documented the knowledge so he can email it to the people who ask. His email is V8FastCars@msn.com
