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  #1  
Old 03-13-2013, 10:55 AM
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jlewis jlewis is offline
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Idle rpm

What should the rpm be at idle for 89 g-wag 360 with a holley truck advenger 670 at cold and hot?
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Last edited by jlewis : 03-13-2013 at 12:13 PM.
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  #2  
Old 03-13-2013, 10:36 PM
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FSJunkie FSJunkie is offline
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When you start it cold and tap the accelerator a few seconds after it starts, idle should be in the 1400-1600 RPM range in park or neutral.

On a completely warm engine, 650-750 in gear usually works best.

BTW, the secondaries on that carburetor are barely going to crack open at WOT. Expect 10 MPG.
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  #3  
Old 03-13-2013, 11:02 PM
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Dr. Marneaus Dr. Marneaus is offline
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Quote:
Originally Posted by FSJunkie
When you start it cold and tap the accelerator a few seconds after it starts, idle should be in the 1400-1600 RPM range in park or neutral.

On a completely warm engine, 650-750 in gear usually works best.

BTW, the secondaries on that carburetor are barely going to crack open at WOT. Expect 10 MPG.

Pretty much what he says.

I'm around 1500 cold and let it run for a min, then tap and in park I'm at about 700-750 and around 550-600 in gear.

This is what was suggested to run by the old guys around here!
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  #4  
Old 03-14-2013, 08:31 AM
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BGW BGW is offline
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Jeeze, you guys like your fast idles. Mine sits at 450 in gear when it's warm. Any faster and it fights the brakes when you're trying to stop.
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  #5  
Old 03-14-2013, 08:47 AM
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Quote:
Originally Posted by BGW
Jeeze, you guys like your fast idles. Mine sits at 450 in gear when it's warm. Any faster and it fights the brakes when you're trying to stop.
650 is the lowest spec I've ever seen in the books. At my altitude, a low compression 360 barely stays running at 450. 500 might work, but it's certainly not smooth. Even 700 isn't super smooth, 360's just aren't the smoothest idling engines on Earth.

If you want a smooth low idle, get a high compression 327. Their specified idle is 500 and perfectly smooth. They don't get rough untill 400 and below.
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  #6  
Old 03-14-2013, 09:11 AM
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serehill serehill is offline
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Hmm interesting

Quote:
Originally Posted by FSJunkie
650 is the lowest spec I've ever seen in the books. At my altitude, a low compression 360 barely stays running at 450. 500 might work, but it's certainly not smooth. Even 700 isn't super smooth, 360's just aren't the smoothest idling engines on Earth.

If you want a smooth low idle, get a high compression 327. Their specified idle is 500 and perfectly smooth. They don't get rough untill 400 and below.

Mine sits at about 700 in neutral a little less actually.
'
450 in gear.
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Last edited by serehill : 03-14-2013 at 08:16 PM.
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  #7  
Old 03-14-2013, 02:49 PM
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Quote:
Originally Posted by FSJunkie
BTW, the secondaries on that carburetor are barely going to crack open at WOT. Expect 10 MPG.
He can get better than 10mpg I get 14mpg with a really light secondary spring. I don't recall the color but iirc it's two steps from the lightest. Holley carbs can get excelent mileage. My leaky outdated ugly MC4350 only got 8, it didn't smell real rich or anything, it just got terrible mileage.

650-750 should be right where you want it. Our old 87 waggy was set to that and it ran great.
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  #8  
Old 03-14-2013, 03:51 PM
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fulsizjeep fulsizjeep is offline
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Quote:
Originally Posted by FSJunkie
BTW, the secondaries on that carburetor are barely going to crack open at WOT. Expect 10 MPG.
But know that 12-13 is possible.
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  #9  
Old 03-14-2013, 04:15 PM
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BGW BGW is offline
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Quote:
Originally Posted by FSJunkie
650 is the lowest spec I've ever seen in the books. At my altitude, a low compression 360 barely stays running at 450. 500 might work, but it's certainly not smooth. Even 700 isn't super smooth, 360's just aren't the smoothest idling engines on Earth.

If you want a smooth low idle, get a high compression 327. Their specified idle is 500 and perfectly smooth. They don't get rough untill 400 and below.

Maybe not according you, but I can assure you mine runs fine at ~450 even well past 10K elevation. Maybe the early engines didn't like it as much? Either that or the TH400 bogs it down too much to idle that low. The only time I've had trouble with rough idle is when the Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley carb was boiling.
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  #10  
Old 03-14-2013, 04:35 PM
joe joe is offline
 
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The above mentioned ranges are ballpark for 20 plus year old rigs/equipment. Factory TSM specs are written for brand new equipment and for those of us that don't run a brand new motor/carb/ign/trans etc should include a footnote "season to taste". Assuming warm eng/no choke in play in P or N you want your idle low enough to run smooth but not stall when dropping into gear nor high enough where it bangs into gear. Don't worry about high idle with the choke set...whole different parameters not idle set screw related. If you cant get it to idle in P/N in the above ranges you may have to tune the idle mix screws, unrelated to the idle rpm set screw on the linkage. If you've got your idle set screw backed out maximum and it still idles too high, fix your vacuum leak. If you've got your idle set screw turned way in and still idles like crap suspect a blown power valve/carb tune issue. I shoot for around 500-700rpm out of gear, round 500 in gear. Again...there is no exact number...too many variables in play but those numbers work for any AT I've had. The TSM numbers are "guides not must have" readings. If you can't get decent results with the idle set screw "on the linkage not the idle mix screws" in those ranges figure out your other issues before you just randomly start twisting stuff and compound your original issue.
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  #11  
Old 03-15-2013, 11:31 AM
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Perhaps I should open my mouth a little wider before I shoot myself in the foot next time.

Must be the stupid emission controls choking down my stock engine again.

The early motors will idle better than the later ones because the later models have the camshaft retarded 4 degrees over the early engines.

Sure, you can get a 360 to idle at 450 RPM. It's not happiest at it and that low isn't super good for it. No wonder why people complain about low oil pressure. I like an idle that isn't heard or felt, and that happens best at 700 with every 360 I've ever seen.

There is nothing wrong with my THM400. It idles at 800 in park and 700 in drive. That's less of an RPM drop than is being reported here with a TF-727. The TF has even less RPM drop when the engine isn't already at 700 RPM bogs down to 450 in gear. All that says is the engine is not taking the load well.

As for stock ignition timing being too late for a smooth idle, my buddy's '84 Grand Wag had a desmogged and mildly built 360. It still liked 700 in gear and only 750 in park. It would do 500, but it wasn't as happy there. Idled just as smooth as my stock motor. It had higher compression heads, and was more forgiving at high altitude for idle. It's harder for low compression engines to idle up here.
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Last edited by FSJunkie : 03-15-2013 at 10:59 PM.
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  #12  
Old 03-15-2013, 11:41 AM
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fulsizjeep fulsizjeep is offline
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Open wide but the ER visit won't be cheap on the foot. I use my ears to set idle and don't give a rats patootey what the RPM really is.
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  #13  
Old 03-15-2013, 11:43 AM
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Ditto

Quote:
Originally Posted by fulsizjeep
Open wide but the ER visit won't be cheap on the foot. I use my ears to set idle and don't give a rats patootey what the RPM really is.

I set mine by ear.

Footendectimy.
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Edlebrock performer intake
Holley 4180
Msd total multi spark.
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If you can't make it better why waste your time. No use repeating the orignal mistakes. I'm to old to push it that's why.
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  #14  
Old 03-15-2013, 11:45 AM
Ristow Ristow is offline
 
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same hear. i mean here.

Quote:
Originally Posted by fulsizjeep
Open wide but the ER visit won't be cheap on the foot. I use my ears to set idle and don't give a rats patootey what the RPM really is.
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  #15  
Old 03-15-2013, 12:55 PM
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Yeah mine really is set by ear, since I have to throw stock specs out the window with the idle I've got.
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