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#1057148 - 05/03/18 07:55 PM Engine RPM at 80mph  
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juangomez22 Offline
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juangomez22  Offline
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houston tx
I wanted to see if my rpm's were accurate. I am cruising down hwy @ 80mph and my rpms are @ 3k. The 88 SS is all stock 200r4 trans. stock engine 305 stock quadrajet etc..
Is there some kind of post with stock SS rpms and mph quide on the forums etc. ?

#1057150 - 05/03/18 08:43 PM Re: Engine RPM at 80mph [Re: juangomez22]  
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Richie Cat Offline
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Richie Cat  Offline
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Lake Ronkonkoma, N.Y.


83 SC, 355 w/TPI
#1057152 - 05/03/18 11:30 PM Re: Engine RPM at 80mph [Re: juangomez22]  
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juangomez22 Offline
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houston tx
Thank you will this be the same as the original SS specs ? or quide ?

#1057154 - 05/04/18 12:05 AM Re: Engine RPM at 80mph [Re: juangomez22]  
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mmc427ss Online content
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mmc427ss  Online Content
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Pottstown, Pa
Here's an accurate easy to use calculator. Don't forget that a 200R4 has a .67 4th gear. Multiply .67 x 3.73 to plug into calculator, 2.4991 for highway driving. Also don't forget that when the converter locks up in 4th gear the rpm will drop several hundred rpm. You can check that rpm drop by getting the car up to 60 mph and while watching the tach tap the brake pedal which will unlock the converter, note the rpm change.
Standard tire height for an SS is about 25.7". Entering 0 for trans slip will reflect converter being locked up.
The calculator shows 2615 @ 80 mph with 0 slip.

http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php
Bob

#1057173 - 05/05/18 12:10 AM Re: Engine RPM at 80mph [Re: juangomez22]  
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juangomez22 Offline
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houston tx
Thank you mmc427ss, I just think the rpms are too high cruising 80mph @ 3k rpms. I dont remember if this was normal for a stock ss. I think i might swap the 200r4 to a
700r4. I would like to see my rpms around 2500rpms when cruising 80 mph.

#1057176 - 05/05/18 04:45 AM Re: Engine RPM at 80mph [Re: juangomez22]  
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mmc427ss Online content
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mmc427ss  Online Content
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The 700R4 4th gear is .70 so your rpms would go up 5%.
My guess is the tach you are reading is off, stock tachs are not that accurate usually.
Bob

#1057178 - 05/05/18 05:20 PM Re: Engine RPM at 80mph [Re: juangomez22]  
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ChasUno Offline
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Bradenton, FL
Stock tachometers are notorious for going bad as they age. There's a common fault with one of the resistors in the resistor pack that breaks down over time. The tachometer will gradually over read, getting worse until it eventually just pegs out on start up.

Check in the DIY section on this forum, where there's an excellent step by step guide showing how to repair a failing stock tachometer.

Last edited by ChasUno; 05/05/18 05:24 PM.

1986 Monte Carlo SS

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#1057180 - 05/05/18 05:23 PM Re: Engine RPM at 80mph [Re: juangomez22]  
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ChasUno Offline
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Bradenton, FL


1986 Monte Carlo SS

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#1057189 - 05/06/18 02:00 AM Re: Engine RPM at 80mph [Re: juangomez22]  
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Travis Jones Offline
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Travis Jones  Offline
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Ferndale, MI
200-4r is superior in a passenger car to a 700-R4 in EVERY POSSIBLE WAY. If you're having issues with your 200-4r have it rebuilt by reputable rebuilder, forget a 700.


86 SS 6.0L LQ4, TBSS intake, Summit Stage 3 NA Cam, Stainless long tube headers, Stainless 3in exhaust, Microsquirt ECU, FABbot AR5 5-speed, Eaton Truetrac 8.8 LSD, QA1 Lvl 3 Front Suspension, 3-link Rear suspension w/ UMI Control Arms, UMI Front & Rear Braces.
#1057191 - 05/06/18 02:57 PM Re: Engine RPM at 80mph [Re: juangomez22]  
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supernova455 Offline
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tampa, fl usa

#1057192 - 05/06/18 07:24 PM Re: Engine RPM at 80mph [Re: ChasUno]  
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juangomez22 Offline
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houston tx


thank you for this info.. Im bot sure yet if its a tach or tranny issue..

#1057193 - 05/06/18 08:51 PM Re: Engine RPM at 80mph [Re: juangomez22]  
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Witness86SS Offline
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Hatfield, PA
The tach costs about $2 to fix.

Plus you can hook up a tach under the hood and see if that is reading the same.

All easier than digging into the trans first


Justin
1986 Black SS
Upgrades: 350 L05 - Hooker Longtubes - FlowMaster True Dual 2.5" - Electric Cutouts - Electric Fans - Transcooler - Proforged Steering Kit - Astro Shaft - AR62 OUTLAW II Wheels - Energy Suspension Bushings - Bitflipper Chip - 87 ECM - Moog Springs and Ball Joints - Bilstein Shocks - Bucket Seats
#1057233 - 05/10/18 03:52 AM Re: Engine RPM at 80mph [Re: Travis Jones]  
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ChasUno Offline
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ChasUno  Offline
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Bradenton, FL
Originally Posted by thepezking639
200-4r is superior in a passenger car to a 700-R4 in EVERY POSSIBLE WAY. If you're having issues with your 200-4r have it rebuilt by reputable rebuilder, forget a 700.



How come?

Genuine question btw, I have no idea of the differences between a 200-4R and a 700-R4.


1986 Monte Carlo SS

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