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"white" intake valves |
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4417 |
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Posted: Jan/31/2023 at 12:42am |
last week, we pulled the engine and then replaced the rms,
new stock oil pan, and r and r-ed the cross ram intake, due to a leak in the rear wall. while the intake was out i took a look at the intake valves through the head and they all appeared white. my buddies thought that the color indicated leanness, but i disagree, as the engine was dyno tuned and was running quite rich before the tune. tuned to around 11.5-12.5:1 a/f. are some valves simply white in color? wish i had taken pics!!
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6755 |
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Do you have the dyno sheet to post?
An engine will lean out at WOT and 11.5 AF will provide maybe 5 to 10 HP more then 12:5. But 12:5 is a safer place to be. Your lower RPM AF mixture should be higher and not go below 13.8 on a dyno starting readings @ 2500 RPM. A lot of this has to do with fuel and altitude also. IMO you are running lean for maximum HP and you also must know your going to be rebuilding every couple of years to maintain this. If you want longevity over HP, then running a little rich will provide this. White chalky residue could be fuel or fuel additives also that should be cleaned out regularly with an upper cylinder cleaner. The newer GDI intake/turbo cleaners work well. Hard white residue is burnt on from combustion lean condition that in most cases can only be removed by abrasive blasting or solvent soaking the valves out of the engine. |
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Repsolroger
AMC Nut Joined: Aug/23/2021 Location: washington Status: Offline Points: 367 |
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I remember I used to run (trick fuel) a higher octane gas in my motorcycle and around the exhaust it would turn white instead of the black exhaust color and had a different smell....and I'm sure this doesn't help lol
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1969 sst javelin restomod
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sweatlock
AMC Addicted Joined: Apr/28/2014 Location: Largo, FL Status: Offline Points: 3285 |
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Lower than 14.7:1 is ‘rich’ and higher than 14.7:1 is ‘lean’, correct?
The 14.7 refers to the amount of air vs. the amount of fuel (in this case, gasoline), as a ratio of 14.7 parts air to one part of fuel, so the less air present the richer the mixture and the more air present the leaner the mixture. Stoichiometric So why am I stating this? Because 11.5:1 is richer than 12.5:1 and 13.8:1 is leaner.
Edited by sweatlock - Jan/31/2023 at 11:56am |
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6755 |
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Yes, that is correct:
Assuming that the white residue is a lean condition, it's likely happening at cruise speed for buildup to occur. Counter intuitive, but tuning for 12.5 over 11.5 at WOT will usually mean running richer at cruise. 13.8 @ 2500 RPM, close to cruise RPM would be rich. |
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4417 |
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thanks for the replies. i'll find the dyno sheets and post them shortly.
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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BassBoat
AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1713 |
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I agree with the guy that told you white is lean. maybe you had a vacuum leak or tuning problem after the dyno tuning. 12.5 will probably make peak power on a dyno. 11.8 which is "too" rich will give a quicker time at the dragstrip.
Edited by BassBoat - Feb/02/2023 at 10:51am |
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FSJunkie
AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4741 |
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Fuel mixture has little influence on intake valve color in my experience. It does make a world of difference on exhaust valve color, however.
White intake valves could be deposits from additives in the fuel or from a form of corrosion. Aluminum oxide is a white powder. The valves themselves shouldn't corrode, but I suppose that corrosion inside an aluminum intake manifold could leave oxide deposits on the valves. Intake valves usually end up a disgusting gooey brown color from the oil vapors drawn in by the PCV...
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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