idle drop when engine warms up

[futura72]

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.

[LONGHAIR]

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.

[cowboy5683]

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!!

[fiddy9apache]

some may not agree with me but chevys like it hot. my trucks have always ran great at 200-210.

[68gmsee]

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.

[futura72]

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

[rwolf9653]

Originally Posted by fiddy9apache

some may not agree with me but chevys like it hot. my trucks have always ran great at 200-210.

I am nervous by that point. 180 for is good enough for me.

[60ratrod]

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

[MacAttack]

Originally Posted by rwolf9653

I am nervous by that point. 180 for is good enough for me.

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.

[Rollie396]

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.