Timing Issue
#21
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jeff42899 (03-12-2019)
#22
Dr. Detroit
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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.
Jebby
Jebby
#23
Intermediate
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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?
Last edited by jeff42899; 03-12-2019 at 05:58 PM.
#24
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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?
Jebby
#26
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jeff42899 (03-12-2019)
#27
Le Mans Master
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.
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.
Last edited by Bikespace; 03-12-2019 at 09:50 PM.
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jeff42899 (03-12-2019)
#29
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jeff42899 (03-13-2019)
#30
Le Mans Master
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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jeff42899 (03-13-2019)
#31
Intermediate
Thread Starter
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?
#32
Le Mans Master
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?
Please email Lars for his timing papers. It explains all of this, much better than I can hope to.
#33
Intermediate
Thread Starter
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 33@ 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.
Last edited by jeff42899; 03-16-2019 at 03:29 PM.
#34
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That looks like an adjustable vacuum advance, like this Accel unit on Amazon.
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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
#35
Intermediate
Thread Starter
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.
#36
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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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jeff42899 (03-16-2019)