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| #1,and 2 plugs wet and dark, rest are light tan https://slantsix.org/forum/viewtopic.php?t=62702 |
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| Author: | wjajr [ Fri Aug 10, 2018 3:40 pm ] |
| Post subject: | #1,and 2 plugs wet and dark, rest are light tan |
I think the old 390 Holley is leaking fuel after shutdown, and its seems to be draining into #1 & 2 cylinders. The other day I had the front bowl off, checked power valve for rupture and it's OK. Adjusted float level so fuel sloshes out sight hole when leaning into fender, so that's OK. That leaves accelerator pump which I now suspect has some sort of problem, particularly after I adjusted all slop out the actuator lever when throttle is opened, and there is still a slight flat spot underway opening throttle. New rebuild caused a lot of snorting up through carb, which probably didn't help any, and engine still occasionally has a bout of spin back at shut down. Guess I'll get a kit and go through it. |
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| Author: | wjajr [ Mon Aug 13, 2018 6:26 am ] |
| Post subject: | Re: #1,and 2 plugs wet and dark, rest are light tan |
Yesterday while riding around I noticed that A/F gauge was trending into the yellow or ideal zone to lean from steady rich while traveling up a slight grade with small throttle opening increase at 2800 to 3000 rpm. Just for the hell of it I pull #1 & 2 plugs dark wet ones listed in last post; both were a nice tan, no wetness. Granted it has been over night since engine last ran, but still both were much lighter looking as mixture is close to ideal. My A/F gauge only monitors front three due to headers. Also checked #6, it is white with some tan on one side, and whatever that hooked bar spark jumps to is called is tan. So it looks as if the back three are trending lean, and front a bit more rich, why this change in mixture I have no idea. The only change, and now that I think about it, probably has effected combustion is changing lash setting to 0.016" I & 0.016" E from .026" & 028", and over lap of cam is leaning out mixture at higher rpm. I did turn out idle mixture screws 1/8th turn so now their setting is such that a 1/8th turn in or out from that setting changes idle. Total turns out from stop is about 1 5/8th turns. Timing still at +12* From idle of around 850 rpm in park and then increasing rpm I can feel governor kick advancing timing at 1200 rpm as engine rpm seems to transition from straight line increase to much steeper advance. Now that curb idle is 300+ rpm below mechanical advance add point, engine will drop down to 650-700 rpm idle happily when coming to a stop where before it sometimes would not slowdown enough to to get below mechanical kick-in point. I have a 2600 (as advertised) stall converter (more like 2200rpm) so getting into mechanical advance from a stop is not a problem. |
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| Author: | Dart270 [ Mon Aug 13, 2018 7:10 am ] |
| Post subject: | Re: #1,and 2 plugs wet and dark, rest are light tan |
Sounds like your part throttle mixture is just right to me. Maybe just drive it for a while before you dive into the carb? If you see no aluminum specks, then you are fine. Actually, I don't mind seeing some Al specks once in a while, as long as it's not excessive or built up. It has not seemed to hurt my motors. Lou |
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