Idol question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OrangeCrush1970 · 04-26-2008, 12:04 AM

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)

THNX-

Blazer1970 · 04-26-2008, 12:06 AM

If it is a factory tach, it almost definitely reads high. Several hundred rpm high at 3000 rpm is pretty normal.

OrangeCrush1970 · 04-26-2008, 12:16 AM

Sorry, It's an after market Sun Pro.

jhow66 · 04-26-2008, 12:29 AM

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?

Mint68 · 04-26-2008, 01:49 AM

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

cdowns · 04-26-2008, 02:22 AM

american idol is on the fox network

dave2953 · 04-26-2008, 02:38 AM

Quote:

Originally Posted by cdowns

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

GREASEMONKEY72 · 04-26-2008, 04:35 AM

mines about 900 in park and 650 in gear (SB350/TH350)

Longhorn Man · 04-26-2008, 04:46 AM

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.

OrangeCrush1970 · 04-26-2008, 03:44 PM

Quote:

Originally Posted by Longhorn Man

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.

dave2953 · 04-26-2008, 06:48 PM

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.

jhow66 · 04-26-2008, 08:08 PM

Not the tach -the carb set screw.

69halfton · 04-26-2008, 11:03 PM

dave is right, there is only two ways to adjust the tach, the # of cylenders, and the zero adjustment

Bus Ted Knuckle · 04-26-2008, 11:08 PM

I don't think he needs to adjust the tach, he needs to adjust his idle speed screw.

Longhorn Man · 04-27-2008, 02:16 AM

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.

xtreme80 · 04-27-2008, 02:19 AM

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.

OrangeCrush1970 · 04-29-2008, 04:02 PM

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-

04-26-2008, 12:04 AM	#1
OrangeCrush1970 Registered User Join Date: Jun 2007 Location: Smyrna, GA Posts: 709	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) THNX- __________________ *Rottenwood Garage* 1970...71...72 C1500 aka Orange aka Sideshow Bob 540 BB Straub Roller Cam, AFR Magnums, XP 950, TKO 600 2 Tons of Fun

04-26-2008, 12:06 AM	#2
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	Re: Idol question If it is a factory tach, it almost definitely reads high. Several hundred rpm high at 3000 rpm is pretty normal. __________________ Tim

04-26-2008, 12:16 AM	#3
OrangeCrush1970 Registered User Join Date: Jun 2007 Location: Smyrna, GA Posts: 709	Re: Idol question Sorry, It's an after market Sun Pro. __________________ *Rottenwood Garage* 1970...71...72 C1500 aka Orange aka Sideshow Bob 540 BB Straub Roller Cam, AFR Magnums, XP 950, TKO 600 2 Tons of Fun

04-26-2008, 12:29 AM	#4
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	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? __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

04-26-2008, 01:49 AM	#5
Mint68 Registered User Join Date: Nov 2004 Location: Nebraska Posts: 762	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

04-26-2008, 02:22 AM	#6
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Idol question american idol is on the fox network __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

04-26-2008, 04:35 AM	#8
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: Idol question mines about 900 in park and 650 in gear (SB350/TH350) __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME

04-26-2008, 04:46 AM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	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.

04-26-2008, 06:48 PM	#11
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	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. __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250

04-26-2008, 08:08 PM	#12
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Idol question Not the tach -the carb set screw. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

04-26-2008, 11:03 PM	#13
69halfton Registered User Join Date: Apr 2007 Location: King City, Ontario, Canada Posts: 974	Re: Idol question dave is right, there is only two ways to adjust the tach, the # of cylenders, and the zero adjustment __________________ - Jason If you can turn, Youre not going fast enough. Favorite caption: first car to 200 mph in the 1/4 mile, no parachute, drum brakes all the way around.. ..back when men were men.

04-26-2008, 11:08 PM	#14
Bus Ted Knuckle Son of a gun Join Date: Jan 2007 Location: Hot Springs, Arkansas Posts: 1,636	Re: Idol question I don't think he needs to adjust the tach, he needs to adjust his idle speed screw. __________________ Bill BEATERS ARE NEATER

04-27-2008, 02:16 AM	#15
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	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.

04-27-2008, 02:19 AM	#16
xtreme80 Wishin' I had more money! Join Date: Feb 2007 Location: Eugene, OR Posts: 1,242	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.

04-29-2008, 04:02 PM	#17
OrangeCrush1970 Registered User Join Date: Jun 2007 Location: Smyrna, GA Posts: 709	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- __________________ *Rottenwood Garage* 1970...71...72 C1500 aka Orange aka Sideshow Bob 540 BB Straub Roller Cam, AFR Magnums, XP 950, TKO 600 2 Tons of Fun



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