What kind of Idle are you running at stop signs?

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gdizzle

gdizzle

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I am curious, on the 225 slant, in my 66 dart, with super six and elect ignition, what kind of idle should I shoot for when I am at a stop, but in Drive.
Seems I set my idle at about 850, but when i put it in gear it drops to around 600, sometimes 550.

What kind of idle do you guys get at a stop sign?
 
I was talking with some friends the other day about idle at a light in my 225. They said that going from the current oe Carter 1 barrel to a 4-barrel carb setup would smooth out the idle. Should I call 'bs' on that ? Assuming engine was optimally tuned.

Dennis
 
71 valiant with stock 1920 holley. 650ish in gear. I set the hot idle in neutral with the head lights on to 750ish. pulls a steady 17 at idle on the Ole vac Guage. I can't get the mix screw to kill it at idle by going over rich, but I can by leaning. Tried another metering block and screw. But I get it set to wwhere it smooths out and the car idles nice.

what really cleaned it all up was buying NOS made in USA cap and rotors and getting rid of the Chinese junk. Bam. Smoother idle.

second bam. Jet up two on the main jet with an hei ignition. Car has way more oomph when you mat it. Extended tip ngk plugs are a nice light tan.
 
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kelleherdl said:
I was talking with some friends the other day about idle at a light in my 225. They said that going from the current oe Carter 1 barrel to a 4-barrel carb setup would smooth out the idle. Should I call 'bs' on that ?
Click to expand...

Yes, because it is BS. Swapping to a 4bbl on an otherwise-stock Slant motor is a big and ongoing waste of time, money, effort, knuckle-blood, and gasoline, and it damn sure doesn't "smooth out the idle". If your idle isn't smooth, it's because something's the matter. See tune-up parts and technique suggestions in this thread.
 
If you change from a poorly operating carburetor to a good one, that will definitely smooth out your idle in gear. My 69 slant idled terribly for decades. Turns out all the rebuilt Holley 1920 carbs I tried must have been bad. I finally got a good rebuild and it purred like a kitten at idle. They have a sealed idle metering block that gets clogged up and most rebuilders don't address that. That causes it to idle lean, which also makes it touchy to changes in load, like N vs D. All things equal, a 1 good bbl should idle better than a good 4 bbl since the later is a bit over-fueled. For now, try increasing the idle spark advance to at least 10 deg BTDC and might run better. If you don't have a timing light, just turn the distributor until it it idles the best and then watch for pinging going up hills to tell if you went overboard, and pick up a timing light for $2 at a garage sale.
 
I had one that idled at 500 in gear. Thoop-thoop-thoop-thoop-thoop-thoop-thoop-thoop-thoop.........the entire car shook,with every shot.
Stock rebuild 225/904 in a 69 Barracuda.IIRC; a 1bbl.
Thoop-thoop-thoop-thoop-thoop-thoop-thoop-thoop..........
 
My curb idle is only 550 (in park) which puts it around 450 in gear. It idles nice and smooth...Would I have any benefit kicking it up to 650 (in P)?
 
slantsixdan said:
Yes, because it is BS. Swapping to a 4bbl on an otherwise-stock Slant motor is a big and ongoing waste of time, money, effort, knuckle-blood, and gasoline, and it damn sure doesn't "smooth out the idle". If your idle isn't smooth, it's because something's the matter. See tune-up parts and technique suggestions in this thread.
Click to expand...
What is the venturi size and throttle blade size of the 1 & 2 bbl. carbs?

There sizes against a small 4bbl. like a 390 or 450/465?

I'm not so sure I'd call B.S. so fast.
 
kelleherdl said:
I was talking with some friends the other day about idle at a light in my 225. They said that going from the current oe Carter 1 barrel to a 4-barrel carb setup would smooth out the idle. Should I call 'bs' on that ? Assuming engine was optimally tuned.

Dennis
Click to expand...
If the 1bbl is working correctly,and set up correctly, and the engine is otherwise mechanically sound, then the engine will be as smooth as a six can be, with just 3 compression events per revolution.If they idle too slowly, they get to shaking, from the power pulses. Do not confuse this for a poorly set up carb. There is a reason the idle-timing on these old girls is TDC; the pulses are less severe. If you have cranked your timing up, the pulses will be earlier and stronger.
 
JohnnyB said:
My curb idle is only 550 (in park) which puts it around 450 in gear. It idles nice and smooth...Would I have any benefit kicking it up to 650 (in P)?
Click to expand...
The benefit might be a tad more oil-pressure. If you are not experiencing a hesitation on tip in, indicating that the T-port sync is pretty close, and the pumpshot is not delayed, then I see no other benefit from a higher idle.
As long as the TC stays full,lol
 
As to putting a 4bbl on a stock slanty;
in a quest for a smooth idle, is um ,IMO, borderline insane.I have to agree with Dan.And to put one on for any other reason is still insane.

But if you have heavily modded your slanty,well that's another matter.

So as Dan said,if the engine idles rough,and the carb is known to be good, with a correct T-port sync,and fresh enough gas, and the ignition is also known to be good, then it's time to check the mechanicals. Starting with a compression test and a vacuum test.Then setting the valves and a new compression test.And finally if nothing has yet turned up, a leakdown test. One of these will point to the problem;Unless a mistake was made upstream;as in the carb and ignition.
Of course the condition of the PCV is a wildcard. If that baby is flowing too much air at idle, well you just caint tune that out. Or if one of the vacuum devices has a ruptured diaphragm, it might give you a little trouble.Or if your engine is one of those that just plane wants the airfilter house installed to run right, and yours is on the workbench, well you caint tune that out either.Or if the springs in your dizzy..... Well you get the idea;the devil is in the details.
 
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AJ/FormS said:
As to putting a 4bbl on a stock slanty;
in a quest for a smooth idle, is um ,IMO, borderline insane.I have to agree with Dan.And to put one on for any other reason is still insane.

But if you have heavily modded your slanty,well that's another matter.

So as Dan said,if the engine idles rough,and the carb is known to be good, with a correct T-port sync,and fresh enough gas, and the ignition is also known to be good, then it's time to check the mechanicals. Starting with a compression test and a vacuum test.Then setting the valves and a new compression test.And finally if nothing has yet turned up, a leakdown test. One of these will point to the problem;Unless a mistake was made upstream;as in the carb and ignition.
Of course the condition of the PCV is a wildcard. If that baby is flowing too much air at idle, well you just caint tune that out. Or if one of the vacuum devices has a ruptured diaphragm, it might give you a little trouble.Or if your engine is one of those that just plane wants the airfilter house installed to run right, and yours is on the workbench, well you caint tune that out either.Or if the springs in your dizzy..... Well you get the idea;the devil is in the details.
Click to expand...

My friends were talking about my freshly rebuilt slant. Sleeves and all, but nothing other than OE. Well guess what; a nice break-in period and tune-up after that and I am very happy with the idle. Stock carb, choke works just like new. So for me all is well now. I am looking forward to actually working on the slant. Something I have not been able to do since I traded my original Duster in 1980.

Dennis
 
Keep in mind that the higher the idle in an automatic the higher the temp the converter generates.
(Like when sitting at a light in gear.)

One of my friend's had a cam so nasty the engine would not stay running below about 1,600 RPMs so he had to put it in neutral at stops or the trans would overheat.
The part that sucked was it barked the slicks when he put it back in gear and the cops would write him up for exhibition. :D
He got pulled over all the time for that, and he hadn't even started moving yet.
 
My slant is bone stock but the PO did put on a Holley 390 4bbl. It took me a lot of tweaking over the past few year to get it to idle smoothly, but I finally got it all but perfect. 800 or so in park, 650-700 in drive. Part throttle acceleration was a big issue for a while until I got the float level set up correctly. Idle vacuum is 21.
 
gdizzle said:
What kind of idle do you guys get at a stop sign?
Click to expand...

Idle Speed-01.jpg
 
my friends 170 slant six would idle high until we opened the valve lash up now cant even tell its on
 
also having a carter bbd with the two holes on the butterflies will make a slant idle higher than usual. due to extra air flow.
 
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