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Timing Issue

 
Old 03-12-2019, 11:55 AM
  #21  
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Originally Posted by Jebbysan View Post
.Those heads with the fast burn chamber only want about 32-33 degrees total timing Jebby

I have verified that on several dyno tests - don't go the "usual" 36 total with those heads - they like 32 - 33.
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Old 03-12-2019, 03:33 PM
  #22  
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Can I ask you if you had the clearance the rods at all for the roller cam? Some companies are profiling this area enough now after years of complaints from people who ask why is it not done at the factory.

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Old 03-12-2019, 05:52 PM
  #23  
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I backed the timing to 14 degrees with the vacuum detached and the idle is noticeably "lumpier", which I like and sounds great. As soon as I plugged the full vacuum to the distributor the advance jumped to 32. Am I correct in assuming the next target of investigation needs to be the dizzy / weights / springs? Anything jump out in this pic?



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Old 03-12-2019, 06:06 PM
  #24  
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Originally Posted by jeff42899 View Post
I backed the timing to 14 degrees with the vacuum detached and the idle is noticeably "lumpier", which I like and sounds great. As soon as I plugged the full vacuum to the distributor the advance jumped to 32. Am I correct in assuming the next target of investigation needs to be the dizzy / weights / springs? Anything jump out in this pic?

Maybe....but find out where the total timing is, and when it is all in first.....then you can make a better assessment.

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Old 03-12-2019, 06:26 PM
  #25  
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Idle jumps to 900 with vac attached and is at 32. Appears to be all in at about 3k and total is 49.
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Old 03-12-2019, 07:46 PM
  #26  
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Originally Posted by jeff42899 View Post
Idle jumps to 900 with vac attached and is at 32. Appears to be all in at about 3k and total is 49.
With vacuum unplugged at 3k it should be 32-33

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Old 03-12-2019, 09:47 PM
  #27  
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That looks like an adjustable vacuum advance, like this Accel unit on Amazon.

I have one, and I adjusted it to give about 10-12 total degrees of advance. That number may be different for your car's tune. It if was put on without an adjustment, you may be getting too much advance. It sounds like you jumped 18 degrees when you connected the vacuum advance in your idle experiment, which I think is the maximum for that unit.

As mentioned, you want to be at 32-33 degrees total advance (and all-in mechanically) with no vacuum advance (vacuum port plugged), at 3000 rpm. To get all in at 3000 rpm on my car, I think I needed one gold and one silver spring, or whatever the two lightest are (specifically not both the same). You may have mechanical advance left at 3000 rpm.

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Old 03-13-2019, 07:04 PM
  #28  
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Another update. With vac unplugged it's 33 @ 3k and 39 @ 4k. Should I lower the advance at idle? Currently 14 @ 700rpm
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Old 03-13-2019, 07:14 PM
  #29  
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Originally Posted by jeff42899 View Post
Another update. With vac unplugged it's 33 @ 3k and 39 @ 4k. Should I lower the advance at idle? Currently 14 @ 700rpm
You need to install a curve kit in this distributor.
You want all of the timing in by 3000rpm
It should not increase anymore than that.

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Old 03-13-2019, 07:23 PM
  #30  
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Originally Posted by Jebbysan View Post
You need to install a curve kit in this distributor.
You want all of the timing in by 3000rpm
It should not increase anymore than that.
Jebby
You want 33-34 max mechanical. It should occur at 3000 RPM, which you may be able to do just by installing the weaker springs from a curve kit. In the meantime, back the timing down a bit so you max out at 33-34 degrees advanced. Does this occur at 4000 RPM, or does it keep going up? Then the timing will be set, and you only need to adjust the springs.

Did you check to see if your vacuum advance is mechanical? Mine adjusts with a hex key. 1/8" or 3/32", probably. If you can find a part number, you should be able to look up instructions.
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Old 03-13-2019, 07:55 PM
  #31  
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It stops advancing right about 4k. After reading some literature on the curve kits, I think I'm finally understanding this. It looks like I can back down initial timing a little and go with a lighter spring to get where I need to be. According to the kits, the middle spring should get me 23 more advance at 3k (though I'm getting an additional 25 now). That along with lowering initial timing to 10 should do it. Can you mix springs to dial it in closer or does the tension need to be balanced? Can the max advance (25 now) be limited?
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Old 03-13-2019, 08:25 PM
  #32  
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Originally Posted by jeff42899 View Post
It stops advancing right about 4k. After reading some literature on the curve kits, I think I'm finally understanding this. It looks like I can back down initial timing a little and go with a lighter spring to get where I need to be. According to the kits, the middle spring should get me 23 more advance at 3k (though I'm getting an additional 25 now). That along with lowering initial timing to 10 should do it. Can you mix springs to dial it in closer or does the tension need to be balanced? Can the max advance (25 now) be limited?
You can mix one light and one medium spring, for example, to get the max advance point right where you want it. Some kits include plastic bushings and counter weights that can also be used. The bushings can limit the total mechanical advance, but what you have should work. Usually, except for the springs, the curve kit parts are garbage.

Please email Lars for his timing papers. It explains all of this, much better than I can hope to.
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Old 03-16-2019, 03:21 PM
  #33  
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I purchased an advance curve kit and think I'm at a very good place. I ended up using two different springs (one middle and one lightest), and get full advance of [email protected] 3k. This took my initial timing to 12. Idle quality is good and throttle response is also good. I only did a short drive but am very pleased. It does look like I'm getting an additional 18 degrees from vacuum giving me a total of 51. When the weather breaks I'll look into this more. I'd rather have an air temp over 35 degrees to finish dialing it in. Thank you all for your help! It's a different car already.

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Old 03-16-2019, 06:22 PM
  #34  
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Originally Posted by Bikespace View Post
That looks like an adjustable vacuum advance, like this Accel unit on Amazon.
.......
Looks like it .. Hex on can-body ... But Might NOT be.
Asians have mfd look-a-like for some of the cheap asian HEI ... but I have had my hands and eyes on some that did Not have the internal adjust allen screw in it.sux
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Old 03-16-2019, 06:30 PM
  #35  
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It is adjustable. I'm going to wait for a little warmer weather to adjust it. I don't know how the colder dense air will change things do but I do I plan to drive it more in warmer weather. I plan to back it down to around 14 and see how that works out. I'll adjust from there pending how it reacts.
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Old 03-16-2019, 06:51 PM
  #36  
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Originally Posted by jeff42899 View Post
It is adjustable. I'm going to wait for a little warmer weather to adjust it. I don't know how the colder dense air will change things do but I do I plan to drive it more in warmer weather. I plan to back it down to around 14 and see how that works out. I'll adjust from there pending how it reacts.
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