Good discussion and points made so far. Ill try to clear some things up, perhaps.
Originally Posted By: 69GTX
As often as you can swing it, I'd run the truck around the roads whether permitting to get the oil hot. In the cold weather I'd probably block much of the radiator to aid reaching higher oil temps...sooner. Frequent cold starts while not making it to normal oil temp is the toughest on an engine. The extended high idle makes sense. When I used to warm up my old '68 GTX for a run, it would prefer to stay up on high idle (1600-1800 rpm) for quite a while. I'd usually have to slap the accelerator pedal to bring it down or it might stay there all day.
When used for plowing after a snowfall, it gets good and hot. Usually it takes about an hour to clear the place and the oil pan is 200+, measured via non-contact. A few times a year, i sneak it into town (5 miles) for get gas. it's not licensed, insured, or generally roadworthy, so it doesn't see road time as a general practice.
The choke works the same as you describe. when warmed up and ready, it will come off high idle at the slightest touch of the pedal. if it is "sorta warm" and not quite ready, a hard blip of the pedal will force it off the cam, but it settles down into a low and lopey idle telling you it wasn't quite ready. otherwise, yes, it stays on high idle until you tell it not to.
Originally Posted By: Merkava_4
You can adjust that fast idle speed to whatever you want. You can also adjust the choke to stay on longer or pull off quicker. Whatever you want.
the idle speed and choke timing is set about where it needs to be. when cold at first start up, it idles in that 1000rpm ish range. but as the engine warms up and the choke pulls off, the engine speed naturally rises. as stated, it will sit on the high idle cam until i can get back to the truck and hit the throttle to pull it off high idle. when warm, that high idle is in that 2200 rpm ish range, but when cold it is where it needs to be to keep running.
to be quite blunt about it .... this truck starts, unaided no matter how cold. i've started it as cold as -20F and if it can do that ... i ain't touching it.
Originally Posted By: Shannow
It's fine...
2,500RPM is my target warm up speed when I'm trying to get the engine up to speed before hitting the highway.
2,500RPM will generate more heat through viscous friction than 1,500 by a LONG way, so will be minimising the time that you are sitting there with the choke plate washing the walls with fuel.
i've chosen to leave it run at high idle, to help it get fully warmed before shut down. Occasionally, things will go ary and i'll go back and shut the truck off when it's clear that it's going to be a while before i can get whatever the problem is fixed. but otherwise, i just let it run as i've come to the conclusion that it is the lesser of a few evils. I've had to crawl under the truck in the snow more than once because i decided to shut it off, and it ain't no fun! One of two problems usually rears it's ugly head. either the starter is heat soaked (from the headers) or it has gotten wet from pushing snow, and freezes up when it cools down, or both. either way, no fun.
Originally Posted By: UltrafanUK
High idle after a very cold start is not better for lubrication, it's worse and a waste of fuel. If your battery is OK, just start up, wait 30 seconds for the oil pressure light to go out if required and just drive to where you need to go.
Originally Posted By: 69GTX
Originally Posted By: UltrafanUK
High idle after a very cold start is not better for lubrication, it's worse and a waste of fuel. If your battery is OK, just start up, wait 30 seconds for the oil pressure light to go out if required and just drive to where you need to go.
That's the problem. There's nowhere for that truck to go to on most days. It has to be started, yet rarely driven. So what do you do to minimize those negative effects? Chitty Chitty Bang Bang could fly and go somewhere. But, that wasn't any more load on the drive train than idling on the ground.
exactly
the only place the truck needs to go is out of the way. anyone that starts a cantankerous old truck, drives it 50 feet and shuts it off when it is below zero outside gets what they deserve. read: dead truck and cold trying to fix it outside in the cold
My experience tells me that leaving it run is necessary. my opinion, is that leaving it run at high idle is better than leaving it run at low idle. my knees tell me that getting in and out of the tractor repeatedly is not fun.
Originally Posted By: jayg
If you have a volt meter to see the minimum amount of rpm you need to excite the alternator in to generating a positive charge and the lowest RPM where the engine isn't bogging, that's where you want it.
good point. when warm, 800 rpm does all of that. however, that requires me to stop what i'm doing to kick it down. But i remain unconvinced that low idle is better than high idle, in particular regard to cam health (which i belive is already failing, but that's a product of being a SBC with a shady past, at best.
Originally Posted By: CR94
Originally Posted By: Shannow
...
Per OP's post
Originally Posted By: meborder
but the choke opens fully without any help.
Right, but heating the oil faster by fast-idling faster may not "be minimising the time you are sitting there with the choke plate washing the walls with fuel." It would if and only if the choke is a type that reacts to actual engine temperature---as opposed to ambient temperature and fixed timing, like one I had.
it is the factory quadrajet carburetor. the choke, as far as i know, responds to engine temperature, and is not based on time. once my gauge reads above 180, it will usually pull off and stay off high idle.
As a side note, with a 190 degree thermostat (verified with an IR), the engine runs at about 230, according to the mechanical gauge i installed (verified by IR). i blame the stupid location of the factory sensor. surely, the exhaust side of the head right between two exhaust ports is likely to be the hottest part of the engine, and thus the gauge reads 230. BUT .. it runs at 230, all day, every day, no matter the temperature outside, or what it is being asked to do. I used it to haul 4,000 lbs of debrise to the landfill this summer when it was in the lower 90's outside and the gauge still read 230. (yeah, shame on me.... the trailer wasn't licensed either).
good discussions ....
