Best way to cure too much total timing?
07-13-2003, 12:04 AM
#1
Instructor
Thread Starter
Best way to cure too much total timing?
I noticed my motor was knocking during hard acceleration so i checked the timing, with the vacuum adv diconnected at 10 degrees initial timing, i was getting 30 degrees total. When i connected the vac adv it jumped to 46 total. What can cause this? I tried leaving the vac disconnected but i'm running much hotter now. Should i just hook up a adjustable diaphragm?
07-13-2003, 12:13 AM
#2
Drifting
Re: Best way to cure too much total timing? (Steve81)
46 degrees total should be no problem. It should be able to run on premium pump gas with that kind of advance. Look at your mechanical advance and see if it's working right. If so, you can get heavier sets of advance weight springs and experiment with them. That will slow down your advance curve.
07-13-2003, 03:18 AM
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Re: Best way to cure too much total timing? (Steve81)
If the timing is ok, why the knocking? I run 94 high test only.
Another thing would be to verify the timing on the balancer. Sometimes the balancer's outer ring will shift. You won't get an accurate timing measure then.
how hot is it at idle ? What plugs are you using ?
07-13-2003, 08:49 AM
#5
Safety Car
Re: Best way to cure too much total timing? (Steve81)
Excessive temps in the combustion chamber can cause knocking even when the timing is right. It can get hot enough in there to make casting bumps in the chamber glow red hot which can ignite the charge early causing the knocking. It can can really be a problem on higher compression engines. Knocking down the casting bumps by polishing the combustion chambers can help avoid this from happening. if yur mixture is too lean it can cause too much chamber heat too. A spark plug with a colder range might also help. Retarded ignition timing can lead to excessive chamber heat too. Most people think its only advanced timing that can cause knocking. but if the timing is too far retarded to cause excessive heat, then it can lead to knocking. Its a good thing you run high octane and i would stay with it. Your timing as you list it could be advanced some.
I think you should try some things to reduce combustion chamber temps. This is what I wouild recomend doing to do that.
1. Pull your plugs and check for carbon deposits. If theyre not black and sooty then yur not too rich. Replace the with plugs that are one step colder in heat range. IE: If yur running r44 the switch to r43.
2. If yur plugs were not sooty then you could probably increase the jets 2 sizes without any ill effects. The richer mixture will help cool things down and might give you some more power to boot.
3. Advance the timing till you get 14 initial and 34 total with vac dis-connected. Then connect vac to ported source on the carb. Ported source has no vacuum at idle. The advanced timing will also help cool things down.
After making these changes you will surely need to re-adjust the curb idle speed and idle mixture screws.
Im running at least 10.5to1 compression with an CR43ts plugs and 12 initial and 36 total with and aditional 12 of ported advance. My combustion chambers are polished and I run high test pump gas. I jetted my carb up 1 size in the primarys and 3 sizes in the secondaries. I have never heard a single ignition knock from my engine. Even when its running hotter.
[Modified by Jvette73, 7:52 AM 7/13/2003]
I think you should try some things to reduce combustion chamber temps. This is what I wouild recomend doing to do that.
1. Pull your plugs and check for carbon deposits. If theyre not black and sooty then yur not too rich. Replace the with plugs that are one step colder in heat range. IE: If yur running r44 the switch to r43.
2. If yur plugs were not sooty then you could probably increase the jets 2 sizes without any ill effects. The richer mixture will help cool things down and might give you some more power to boot.
3. Advance the timing till you get 14 initial and 34 total with vac dis-connected. Then connect vac to ported source on the carb. Ported source has no vacuum at idle. The advanced timing will also help cool things down.
After making these changes you will surely need to re-adjust the curb idle speed and idle mixture screws.
Im running at least 10.5to1 compression with an CR43ts plugs and 12 initial and 36 total with and aditional 12 of ported advance. My combustion chambers are polished and I run high test pump gas. I jetted my carb up 1 size in the primarys and 3 sizes in the secondaries. I have never heard a single ignition knock from my engine. Even when its running hotter.
[Modified by Jvette73, 7:52 AM 7/13/2003]
07-13-2003, 10:22 AM
#6
Instructor
Thread Starter
Re: Best way to cure too much total timing? (Jvette73)
Most people think its only advanced timing that can cause knocking.
1. Pull your plugs and check for carbon deposits. If theyre not black and sooty then yur not too rich. Replace the with plugs that are one step colder in heat range. IE: If yur running r44 the switch to r43.
3. Advance the timing till you get 14 initial and 34 total with vac dis-connected. Then connect vac to ported source on the carb. Ported source has no vacuum at idle. The advanced timing will also help cool things down.
