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Post by 358t on Apr 28, 2014 14:36:37 GMT -6
Where did anyone say a -8 was colder than a -9?
Actually a -8 is still somewhat cold for his engine but should work.
Too much temp taken away and the plug can misfire. So... the fuel doesn't burn.
What has he had on it... 3 different carbs now? They all miss/pop? Maybe it is fuel related or maybe not. Based on personal testing and helping many others running alcohol, either way the current plugs he is using are not the correct heat range imo . But, what do I know...
Scott
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Post by dennismopar73 on Apr 28, 2014 15:09:06 GMT -6
Where did anyone say a -8 was colder than a -9? Actually a -8 is still somewhat cold for his engine but should work. Too much temp taken away and the plug can misfire. So... the fuel doesn't burn. What has he had on it... 3 different carbs now? They all miss/pop? Maybe it is fuel related or maybe not. Based on personal testing and helping many others running alcohol, either way the current plugs he is using are not the correct heat range imo . But, what do I know... Scott The thinking that 8 is a cold plug. 8 is hot in NGK plugs . 10 - 11 is cold Anyhow. Won't beat that horse anymore I was.in the stands I heard some pops in the water box , And couple in his shift other than.that it was clean after that As it stands I'm still thinking fuel delivery , and possible wiring issue. Jmo So. In all honesty. What plug would you run ?? We are all beating our brains and throwing out stuff . Plugs are cheap .
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Post by dennismopar73 on Apr 28, 2014 15:18:36 GMT -6
Understand , never had issue till now Under several several jet changes
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Post by 548h on Apr 28, 2014 15:20:50 GMT -6
Put it on a chassis dyno. Put an ignition scope on it, AFR and timing light. Let her eat and you should see something helpful.
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Post by 358t on Apr 28, 2014 15:38:57 GMT -6
Where did anyone say a -8 was colder than a -9? Actually a -8 is still somewhat cold for his engine but should work. Too much temp taken away and the plug can misfire. So... the fuel doesn't burn. What has he had on it... 3 different carbs now? They all miss/pop? Maybe it is fuel related or maybe not. Based on personal testing and helping many others running alcohol, either way the current plugs he is using are not the correct heat range imo . But, what do I know... Scott The thinking that 8 is a cold plug. 8 is hot in NGK plugs . 10 - 11 is cold Anyhow. Won't beat that horse anymore I was.in the stands I heard some pops in the water box , And couple in his shift other than.that it was clean after that As it stands I'm still thinking fuel delivery , and possible wiring issue. Jmo So. In all honesty. What plug would you run ?? We are all beating our brains and throwing out stuff . Plugs are cheap . Not intending to beat the horse here either but this is where the different interpretations come in. A -8 is not hot. It is medium-cold A -6 or 5 is hot. -9 is the coldest virtually any naturally aspirated engine should ever need and that is if it has high compression, makes a lot of power, and/or has a small camshaft for the compression. Have you guys pulled a plug and looked at them? I bet they don't show any heat do they? If they show moderate to high heat then it is definately lean. If no heat or even wet it could be indicating too cold of a plug or too rich. But he tried changing jets and no change although that doesn't rule out fuel delivery. So, what do the plugs look like? I already said what I think is the coldest plug it should have and what plug I think it should have in it in previous posts. Here is a chart that might be helpful I'm not saying for sure the problem is the plugs just that a -9 or -10 heat range and short tip plug definately isn't helping matters. Just weird that all he did was rebuild the engine and put a roller cam in it and now it has this miss/pop. If the new cam has more duration and/or a later intake closing it can have less cylinder pressure than before and therefore not put as much heat into the plug and therefore not tolerate a cold plug like a -9 or -10. Scott
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Post by 358t on Apr 28, 2014 15:55:41 GMT -6
Years ago I think it was Greg Sesti chased a miss/pop for weeks. IIRC the problem ended up being the pass through coil terminal he had mounted on the firewall.
Scott
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Post by dennismopar73 on Apr 29, 2014 4:58:49 GMT -6
Plugs clean look great . I'm leaning hard with three areas. Still a fuel delivery issue, wiring issue, Valve springs to weak,
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Post by racerone on Apr 29, 2014 11:48:18 GMT -6
Thanks guys . I ran the ar3911 few years back don't remember any issues then So is the Ngk a reverse heat cold range verses autolite ? I had 10 thinking cold had 9 in beginning of year ? C&S mentioned going to a Ngk 8 they have my carb hoping to get it back wed might hit track .
I run flat top pistons so I'm not sure now if the auto lites ar3911 were long tips and considered what heat range also .
Roger at C&S seems to feel top of rpm might be alky foul verses gas could cleanup .say same for idle low rpm alky clean gas would run crappy .
So if fouled in a Ngk colder or hotter by the number I run ? Thanks Dr
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Post by 358t on Apr 29, 2014 12:08:06 GMT -6
Autolite AR3911 is the same heat range and style as a NGK R5672A-8 which is an extended tip plug. The R5671A series is the short tip plug.
I am currently running the AR3911 in my engine.
In NGK, 10 is colder than a 9. Lower number is hotter in NGK plugs. Higher # is hotter in Autolite plugs. The cross reference table I posted able should make it easier to see
Scott
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Post by dennismopar73 on Apr 29, 2014 16:40:01 GMT -6
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Post by dennismopar73 on Apr 29, 2014 17:01:49 GMT -6
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Post by racerone on Apr 29, 2014 19:04:53 GMT -6
I ordered Ar3911 and now have 2 Dom for my testing which I run a 950 normally. C&S cant get mine done for over a week I guess I should have asked when as they knew I have been chasing this . I feel the fuel system is good to carb now . Scott thanks for the clarification on the plugs . Dennis thanks also But Who can read a Alky plug unless its really messed up .
If it still pops I will foot brake and shift it with all my stuff disconnected again to see if it pops still . Thanks again .
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Post by sg3526 on Apr 29, 2014 19:21:35 GMT -6
I ordered Ar3911 and now have 2 Dom for my testing which I run a 950 normally. C&S cant get mine done for over a week I guess I should have asked when as they knew I have been chasing this . I feel the fuel system is good to carb now . Scott thanks for the clarification on the plugs . Dennis thanks also But Who can read a Alky plug unless its really messed up . If it still pops I will foot brake and shift it with all my stuff disconnected again to see if it pops still . Thanks again . I have a Q-950A you can try if you want to try Alcohol on it. Not doing anything but sitting on a shelf here.
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Post by 358t on Apr 29, 2014 20:12:25 GMT -6
Don, it is tough to read an alky plug especially naturally aspirated. You won't see any discoloration like gas does. What you need to look for is heat in the strap. If the plug is too cold you won't be able to get any heat without running it way too lean. If not enough timing it may not show any heat on the strap. Look to get the heat mark at about the bend as that indicates the correct timing. If the whole strap is discolored from heat then it has too much timing or is way too lean.
Scott
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Post by dennismopar73 on Apr 29, 2014 20:44:03 GMT -6
Don I really hope you get this figured out , Good luck with the plugs,
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