Idle speed
FTE Legend
Joined: Nov 2015
Posts: 30,860
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From: Angier, NC
Here in the USA they put a sticker on the radiator with tune up spec and one should be idle speed. Do they do the sticker down under?
Dave ----
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Joined: Nov 2007
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From: Denver Metro Area, CO
A bang noise can be the idle speed is too high (do you have a tachometer yet? You need tools if you're going to own and work on an old truck like this) but it could also be pointing to loose U-joints or, more commonly, the ring & pinion in the rear end. Get yourself some actual tools so you can do some work based on actual data and not just guesses.
FTE Legend
Joined: Jul 2010
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From: Northeast, OK
Idle speed isn't dependent on what carb you have, but you have a ThermoQuad? My memory is failing as I thought you have a QJet.
Regardless, I personally don't set idle speed with a tach. (I'm not saying you don't need tools, as I agree with Chris.) Idle speed needs to be just fast enough that the engine doesn't die, but slow enough that you don't hurt the driveline when you put it in gear. So, it is a compromise.
However, the vacuum advance can play a big part in this if you have it connected to manifold vacuum. And, since you probably aren't running the original carb then someone has been playing with things and it would be easy to have manifold vacuum to the advance - which means you have vacuum to the distributor at idle. If so, you may not be able to get a stable idle speed and the engine will need to be racing when in Neutral, but may bog when put in Drive. If that's the case, I strongly recommend you find "ported vacuum" for the vacuum advance, meaning there is no vacuum at idle and the vacuum comes in as you crack open the throttle.
Regardless, I personally don't set idle speed with a tach. (I'm not saying you don't need tools, as I agree with Chris.) Idle speed needs to be just fast enough that the engine doesn't die, but slow enough that you don't hurt the driveline when you put it in gear. So, it is a compromise.
However, the vacuum advance can play a big part in this if you have it connected to manifold vacuum. And, since you probably aren't running the original carb then someone has been playing with things and it would be easy to have manifold vacuum to the advance - which means you have vacuum to the distributor at idle. If so, you may not be able to get a stable idle speed and the engine will need to be racing when in Neutral, but may bog when put in Drive. If that's the case, I strongly recommend you find "ported vacuum" for the vacuum advance, meaning there is no vacuum at idle and the vacuum comes in as you crack open the throttle.
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Joined: Jul 2015
Posts: 102
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From: Victoria, Australia.
I hav an aftermarket saas tachometer, I've got plenty of tools boys, I've checked the u bolts on the driveshaft and the yoke on the rear end they are tight but in not quite sure on the vacuum settings you guys mentioned but my truck definitely bangs when you put it in gear so do you guys recommend starting off with dropping the idle speed right down till it stops the bang, I think it goes idle at the moment is sitting on about 850 rpm and it is still banging, so I might drop it down to about 500/600 rpm and see if it still bangs, is that what you guys think is the best place to start of with or........?
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Joe Kucinski
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Joined: Nov 2007
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From: Denver Metro Area, CO
I mostly agree with Gary - yes & yes - but IIRC the idle speed with an automatic transmission is around 700 or so BUT I'm just goig on way way way old memory... I think they want you to set it with the transmission in Drive, too, but you should check the procedures as I don't remember too well (I don't drive an automatic transmission very often and have owned only two in my life).
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