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10-23-2009, 01:56 AM | #1 |
Registered User
Join Date: Aug 2006
Location: Portland
Posts: 14
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idle drop when engine warms up
i recently changed out my head and intake gaskets, changed the oil, set timing and adjusted my carb. it runs really strong and idle seems to be good until it gets fully warm (20 minutes+ drive time, highway). after that, when i come to a stop, my rpms drop (no tach, i notice the battery drops from 14.3 to 12.5). it doesn't seem to want to die, but not sure why it is dropping so low. should i adjust the timing at this point or the idle speed once the engine gets this warm? after the thermostat swap, it doesn'tgo above 160 degrees while driving... not sure what i am looking to do here. thanks.
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10-23-2009, 06:30 AM | #2 | |
just can't cover up my redneck
Join Date: May 2004
Location: Columbus OH
Posts: 11,414
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Re: idle drop when engine warms up
A lot of how the cooling system performs has to do with the over-all efficiency of the radiator and the air-flow through it.
For example, adding a lower temperature thermostat to a system that cannot "keep-up" does nothing but open earlier. If the radiator can't get rid of enough heat to keep the coolant at that lower temperature, nothing changes. This of course has something to do with the engine itself and how much heat it makes and the temperature of the air over the radiator too. But, if the system is "borderline" in it's ability to cool, a lower temperature thermostat will not fix it. On the other hand, if your system does cool well (smaller engine, big radiator, good air-flow, etc) it is possible to "over-cool". This means slower warm-ups, lower temp air from the heater/defroster, and possibly poor performance. All of your "tuning" should be done with the engine "fully warmed-up" but it should still idle well cold too. You may need to step up the thermostat and do some choke tuning. A 180 degree t'stat will get you warmed-up quicker, run in a better temp range, improve your heater and maybe even fuel mileage. Then you just have to get the choke set right to get it to idle when cold.
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10-23-2009, 06:34 AM | #3 |
Registered User
Join Date: Jun 2009
Location: San Bernardino CA
Posts: 94
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Re: idle drop when engine warms up
All of yer timing and carb adjustments should be done once its all warmed up anyways..So once its all warmed up I would check yer timing first..get it set..then adjust idle then go through the air/fuel adjustment process..then after air fuel adjustment recheck idle and adjust as necessary..Then verify yer choke is adjusted properly(fast idle etc..) and all should be well in chevy land again..as far as the thermostat goes..are you sure you got a 180 or 195 thermostat?..if so..you may have got a bad one and you should go get a new one..Personally I rely on stant products..good luck!!
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10-23-2009, 07:41 AM | #4 |
Registered User
Join Date: Aug 2009
Location: ftw tex
Posts: 682
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Re: idle drop when engine warms up
some may not agree with me but chevys like it hot. my trucks have always ran great at 200-210.
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10-23-2009, 10:33 AM | #5 |
Active Member
Join Date: Jul 2007
Location: Centrally located between Houston, Austin and Waco. BCS area.
Posts: 7,947
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Re: idle drop when engine warms up
I agree with the adjusting when warm.
160 seems low. Engines and carbs are made to run hotter than that. Mine was running slightly higher than I like so I went to 180 degrees, installed an overflow tube (home-made) and now my truck stays at 185-190. That's normal for my truck. |
10-23-2009, 11:30 AM | #6 |
Registered User
Join Date: Aug 2006
Location: Portland
Posts: 14
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Re: idle drop when engine warms up
180. not a problem. at least it seems an easy fix. as soon as the temp jumped over 160 for any reason, that is when the idle drops. thanks for the help! i need to get some pics of my truck up here. 2nd owner of a 72 c-10 swb. only 19 years in my possession and i'm finally getting isht done
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10-23-2009, 11:38 AM | #7 |
more ideas than money
Join Date: Dec 2008
Location: spring grove, pa
Posts: 1,068
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Re: idle drop when engine warms up
I am nervous by that point. 180 for is good enough for me.
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Randy 1948 Chevy 3100 5 window 1966 Chevy C30 Dually 1967 Chevy K10 1972 Chevy K20 1972 Chevy C10 1972 Chevy K5 Blazer 1987 Chevy V10 2003 Chevy Suburban Last edited by rwolf9653; 10-23-2009 at 11:39 AM. |
10-23-2009, 03:46 PM | #8 |
yes, i do
Join Date: Jun 2007
Location: Spokane, wa
Posts: 2,734
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Re: idle drop when engine warms up
unless my vehicle is a FI unit, i always run a 180 t-stat. and i agree with the stant comment. i have never had any issues with a stant. but i wouldn't go to a csk, oriely's, or auto zone for one since they are carrying motor rad stuff now. haven't had good luck with the motor rad stuff
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ERROR 404....... SNAPPY COMEBACK NOT FOUND _______________________________________________________________________________________________ -60 Chevy C10, dead 350/good th350 combo, sitting on a 76 c10 blazer frame, built from 11 different vehicles "the abomination" -07 gmt900 silverado 1500 lt xcab z71, granite blue -81 suzuki gs650g "shelah"- current project -81 kz1000m1 csr "sarge" -next project (just beautification) -07 kawasaki vulcan classic vn900 |
10-23-2009, 04:35 PM | #9 |
283 Drama Queen
Join Date: Dec 2004
Location: Surf City, CA
Posts: 2,435
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Re: idle drop when engine warms up
I went through a similar hassle with the new '283' and bought this from Summit:
Milodon Thermostat 180 Deg High-Flow Copper/Brass The post 1985 motors love the higher operating temperatures, but if you've got old metal - don't run on the highway at the higher numbers, or you won't for long. Mac.
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10-24-2009, 12:34 AM | #10 |
someday it will be done!
Join Date: Sep 2004
Location: Lloydminster,AB. Canada
Posts: 1,620
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Re: idle drop when engine warms up
The 283 in my 66 ran at 200 for 8 yrs,highway,dirt road or no road.Didn't use a drop of oil and never let me down.
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'72 C-10 Proud owner of a million new and used pieces that used to be and will once again be(god willing) a testament to the term "they don't build em like that anymore. '80 LWB 2wd beater '67 GMC long fleet (cab donor) '66 long step (parked till it's turn comes around) '65 short step (parts truck that will donate it's bed and possibly frame to the '66) '06 Grand Prix wife's car (she hardly lets me touch it) my pics |
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