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Jon H


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RPM Calculator
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Mitch wrote:

  Time for that 200r4 with a lock-up converter to lower the rpm's....stirpot 

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I am about ready to pull the trigger on the 200 4R (once I get this oil sucking POS rebuilt next month) although the tranny builder reccommends against the lock-up and talking to Pushrod, he has actually disconnected his and says it operates a lot smoother without it.  Yes-no-maybe?  headscratch



-- Edited by Jon H on Sunday 12th of August 2012 01:20:01 PM

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'69 Convertible,  Lemans Blue, 454, 200 4R, 12 Bolt. 

Jon H.  Lino Lakes
Jon H


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I was looking at several rpm calculators and they seem to vary some, but not drastically. 

The real question is:  I have 3.55 gears with 275x60x15 rear tires.  The tire calculator shows these to be 28" diamater.  Under weight they are 26.5". 

Which diamater do I use?  headscratch

Are there other factors involved?  headscratch

The calculators show at 70 mph with 3.55 gears and a 28" tire an rpm of 3062 and a with 26.5" tire an rpm of 3235.  My tach is showing 3500.  Why the difference, assuming my tach is accurate? headscratch



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'69 Convertible,  Lemans Blue, 454, 200 4R, 12 Bolt. 

Jon H.  Lino Lakes
Lost in the 60s


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There's no way that tire is deflecting 1.5 inches under load. That's half the sidewall height. It would overheat and blow out.

I ran some variations on ratio and tire height too and I'm thinking your tach is off, since none of the calcs match 3500 rpm...dunno



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Mitch D.   River Falls, WI

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1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20
Derek69SS


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Converter slip is usually over 10%, so your tach is probably right on.

I'd go with what the actual tire height is with weight on it.

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Derek Kiefer - Mantorville, MN

69 Malibu Pro-Touring stroker LS1-383/T56 - 69 SS396-325/3spd project
Jon H


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Lost in the 60s wrote:

There's no way that tire is deflecting 1.5 inches under load. That's half the sidewall height. It would overheat and blow out.

On a remeasure I am getting 27.25.  Originally I only measured center cap to floor and doubled it which I think threw it off.  I am running a 7" wheel   instead of 8", would that reduce the diameter a little?

 

 



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'69 Convertible,  Lemans Blue, 454, 200 4R, 12 Bolt. 

Jon H.  Lino Lakes
Lost in the 60s


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Jon H wrote:
Lost in the 60s wrote:

There's no way that tire is deflecting 1.5 inches under load. That's half the sidewall height. It would overheat and blow out.

On a remeasure I am getting 27.25.  Originally I only measured center cap to floor and doubled it which I think threw it off.  I am running a 7" wheel   instead of 8", would that reduce the diameter a little?

 

 

The .75 lower height is the loaded diameter, which is accurate. A narrower wheel can make a tire taller due to crowning, not lower.

I forgot about converter slippage too. Derek is probably right about the tach. It may still have an error percentage coupled with converter slip which will get you where you are.

Time for that 200r4 with a lock-up converter to lower the rpm's....stirpot

 



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Mitch D.   River Falls, WI

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1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20
SShink


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John at Master Trans gutted the electronics in my 200-4R and made it pressure driven overdrive only.  He used an 11" 2400 rpm stall converter, and it worked great around town or on the highway with both the 4.10's and 3.42 gears that I ended up with.  It probably lost a couple hundred rpm locking up on the highway this way vs. an electronic lockup, but it still only ran 2500 at 70 mph with a 26" tall tire.  With your taller tire, it would probably run less than 2500 at 70 mph.

This setup worked great around town, and it would shift into OD a 40 mph, but upshift into 3rd as soon as I touched the throttle.  Somehow I lucked out on the TV cable/carb linkage adjustment, and it worked great.  I'd recommend this setup.  Give John at Master Trans a call in Rosemount if you have questions on how he set it up.



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Jon H


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SShink wrote:

John at Master Trans gutted the electronics in my 200-4R and made it pressure driven overdrive only.  He used an 11" 2400 rpm stall converter, and it worked great around town or on the highway with both the 4.10's and 3.42 gears that I ended up with.  It probably lost a couple hundred rpm locking up on the highway this way vs. an electronic lockup, but it still only ran 2500 at 70 mph with a 26" tall tire.  With your taller tire, it would probably run less than 2500 at 70 mph.

This setup worked great around town, and it would shift into OD a 40 mph, but upshift into 3rd as soon as I touched the throttle.  Somehow I lucked out on the TV cable/carb linkage adjustment, and it worked great.  I'd recommend this setup.  Give John at Master Trans a call in Rosemount if you have questions on how he set it up.

 He is the one that reccommended the non-lock-up.



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'69 Convertible,  Lemans Blue, 454, 200 4R, 12 Bolt. 

Jon H.  Lino Lakes
Lost in the 60s


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Jon H wrote:

I am about ready to pull the trigger on the 200 4R (once I get this oil sucking POS rebuilt next month)

-- Edited by Jon H on Sunday 12th of August 2012 01:20:01 PM

GM is now going to overhaul the current engine to fix the issue ??

 



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Mitch D.   River Falls, WI

Lifetime member of the "Cars apart Club"

1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20
Jon H


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Lost in the 60s wrote:
Jon H wrote:

I am about ready to pull the trigger on the 200 4R (once I get this oil sucking POS rebuilt next month)

-- Edited by Jon H on Sunday 12th of August 2012 01:20:01 PM

GM is now going to overhaul the current engine to fix the issue ??

 

 I thought you had heard, yup.  Happy days ahead, I hope.



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'69 Convertible,  Lemans Blue, 454, 200 4R, 12 Bolt. 

Jon H.  Lino Lakes
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