All B's had the same ratio (3.90:1) except for automatics and V8's (OK,
C's as well). And 3500rpm should be right in the fat of the power band
(such as it is), and corresponds more-or-less with low 60's mph. So I
would think you are having a power problem and not a ratio problem. For
further evidence, my 66B even in OD will pull right on up to 4000rpm no
problem, and beyond. The apparent speedo error is small enough to be
caused by non-stock tire size (I would think), though there are different
ratio speedo drive gears (for OD transmissions, I think) so one may have
been substituted.
Think of it this way -- not being able to pull a high rpm at speed
indicates too low a numeric ratio for the power available (say, 3:07).
But your speedometer error (reading high) would indicate a
higher-than-expected ratio (4:55 for example); or, as I suspect, low
profile tires. So my suspicion is, too little power available for the
stock ratio.
Ben McCoy had this to say:
>...Now I have a question. I had the extreme pleasure of
>driving a beautiful 69 B about 250 miles on I-40 this past weekend. The car
>drove nicely, although I was cautious, the car was purchased the same day I
>drove it. My problem was that the car would not move. I was on the
>interstate and wanted to get the car up to about 70 or so, but it would not
>do it. The speedo would register about 65 at about 3500 RPM in forth, but
>traffic was flying by me and the driver my chase vehicle said we were only
>doing 58 MPH or so.
>
>Now the background: In the pre-purchase evaluation it was determined that
>differential had issues and the rear axle was changed out. Is it possible
>that the rear end that was put in the car was of a different ratio that the
>original? Did OD transmission B's have different ratios that non
>overdrives? Or something like that. This is a minor issue that I don't
>think will affect the around the town driving that this car will see, but I
>am curious.
>
>I have not owned a B for some time and no longer have the resources to look
>the answer to this question up. I remember my B being much faster and even
>had some nice police officers verify the accuracy of my speedometer on
>several occasions. If anyone has any input it would greatly appreciated.
>
>Ben McCoy
>57 MGA
>
>
--
===============================
Max Heim
mvheim@studiolimage.com
Studio L'Image/San Francisco
415 643 9309 : 415 643 9307 fax
Studio L'Image/New York
212 242 3366 : 212 242 3399 fax
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