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Old 04-26-2008, 12:04 AM   #1
OrangeCrush1970
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Idol question

Im trying to figure out if my Tach is correct.
What is normal RPM while sitting still w/ the truck in Drive? Mine show's about 800-900 RPMs at a steady idol. It reads 3000 rpm at 65 mph.
(I have a TH 350 w/ a 3.07 rearend)

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Old 04-26-2008, 12:06 AM   #2
Blazer1970
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Re: Idol question

If it is a factory tach, it almost definitely reads high. Several hundred rpm high at 3000 rpm is pretty normal.
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Old 04-26-2008, 12:16 AM   #3
OrangeCrush1970
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Re: Idol question

Sorry, It's an after market Sun Pro.
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Old 04-26-2008, 12:29 AM   #4
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Re: Idol question

Any figure you want it to be. You can set the speed where you want with the idle screw. 800 to 900 seems a little high for drive. What is the rpm in park?
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Old 04-26-2008, 01:49 AM   #5
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Re: Idol question

If it is an auto that is too high, sounds correct for a 4spd though. My blazer seems to always be low when in drive, like 500-600 rpm. It sometimes drops to 400 when the a/c is on.

Try this link, someone posted it a while back:

http://www.ringpinion.com/Calculators.aspx
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Old 04-26-2008, 02:22 AM   #6
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Re: Idol question

american idol is on the fox network
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Old 04-26-2008, 02:38 AM   #7
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Re: Idol question

Quote:
Originally Posted by cdowns View Post
american idol is on the fox network
You beat me to it cdowns; I was going to suggest this be moved to GD until I opened the thread and saw what he meant.
To answer your question, I have mine set to ~800
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Old 04-26-2008, 04:35 AM   #8
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Re: Idol question

mines about 900 in park and 650 in gear (SB350/TH350)
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Old 04-26-2008, 04:46 AM   #9
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Re: Idol question

depending on the rear tire size, 2500 is more acurate for 25 MPH with 3.07's.
I would say you are a bit high, and your idle sounds like it is reading high too. If it were that high at idle, then it'd be about 1000 - 1100 in park, and that would start to border line slaming into gear.
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Old 04-26-2008, 03:44 PM   #10
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Re: Idol question

Quote:
Originally Posted by Longhorn Man View Post
depending on the rear tire size, 2500 is more acurate for 25 MPH with 3.07's.
I would say you are a bit high, and your idle sounds like it is reading high too. If it were that high at idle, then it'd be about 1000 - 1100 in park, and that would start to border line slaming into gear.
You are correct, it is at about 1000 rpm's in park.
How do I adjust the idol, or the tach? It's one of the smaller Sun Pro tach's and I have no idea how to change it.
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Old 04-26-2008, 06:48 PM   #11
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Re: Idol question

My Sun Pro tach has a a place on the back that will let you set the "zero" adjustment when the engine is off, and it has a selection switch for the number of cylinders. Those are the only two adjustments that I know of.
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Old 04-26-2008, 08:08 PM   #12
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Re: Idol question

Not the tach -the carb set screw.
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Old 04-26-2008, 11:03 PM   #13
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Re: Idol question

dave is right, there is only two ways to adjust the tach, the # of cylenders, and the zero adjustment
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Old 04-26-2008, 11:08 PM   #14
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Re: Idol question

I don't think he needs to adjust the tach, he needs to adjust his idle speed screw.
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Old 04-27-2008, 02:16 AM   #15
Longhorn Man
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Re: Idol question

why do you think it's idling high? His tach is reading way too high at a specified speed.

When you run it in park, and put it in drive, does it clang into gear. or maybe lean over from engine torque... or does it just drop the idle a tad and act like a normal vehicle?
You guys are forgetting, these tachs are stupid cheap and not exactly high quality. I figured when Snap On bought out sunpro, that there quality would go up... but nothing.

Last edited by Longhorn Man; 04-27-2008 at 02:17 AM.
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Old 04-27-2008, 02:19 AM   #16
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Re: Idol question

I have a th350 with a 3.73 rear end and mine's at 2900rpm at 65. My th350 with the 2.73 rear end was at about 2300 at 65.

I think your tach is reading slightly high. Also, my idle is at about 600 in gear.
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Old 04-29-2008, 04:02 PM   #17
OrangeCrush1970
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Re: Idol question

idol at park = 1000 rpm's
idol sitting still in drive = 800 rpm's
idol at 65 mph = 3000 rpm's

doesnt seem to be slamming into drive. it's a nice transition. i think my tach is reading too high-
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