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MG MGB GT V8 Factory Originals Technical - Help V8 Conversion (Speedo/Shocks/Engine Whistle)

I have been working with my mechanic finishing up a 3 year V8 restoration of my 1980 MGB. It has the 3.9 litre Aluminum block with a T-5 transmission.
A couple of details I would appreciate some info on.
1. The original speedometer seems to be about 17% to 18% off (to fast); my mechanic says we need to change the gear fitting into the transmission, but to what? (14” tires, original rear end)
2. The ride seems a little different, not as smooth. I put new shocks in 1991 (always maintained) with 50,000 miles on the car. The restoration started in 2007 with 120,000. My mechanic says the shocks are fine, its just the car is a bit heavier than before. I would say the car is the same or lighter and it needs new shocks. Any thoughts would be welcomed.
3. The engine seems to whistle when idling (10,000 rpms), as I give it a little gas, rpms go up, the whistling stops. Any thoughts?
ricmgb

1. Probably easier to get a reduction gear, or recalibrate the speedo, but then again I don't know how easy it is to change the gears in the gearbox or obtain alternatives. A 1980 MGB would originally have had a 1000tpm speedo (printed on the dial), 4-synch chrome bumper cars had a 1280tpm, one of those would probably be a better match if you can get one the right size (they were used in the UK from 67 to 74).

2. If the car was heavier it would be down on the springs, and may be bottoming. Or if it's lighter it could be higher and 'topping'. Have a look at how bowed or straight the rebound straps are, the springs should be nearly flat and the rear shackles pointing down and back. Can't see the dampers causing a change in ride quality, but if the car has become significantly lighter then they may be too stiff, but then the suspension would be fully raised.

3. Idling at 10,000? I'll take that as 1000. Could be a vacuum leak, but as it is doing it at idle then poke around with a length of hose stuck in your ear.
PaulH Solihull

It’s very easy to change the gear in a Borg-Warner transmission. You just pull out the gear retainer, that’s the part that the speedometer cable screws onto and it’s held in by an O-ring. Once it’s out you can easily remove the plastic gear. You can then count the teeth it has and calculate how many teeth it should have to read 17-18% different. It’s been a number of years, but I seem to remember the price being about eight dollars at the local Chevrolet dealer. As it turned out, I miscalculated what I needed so exchanged it for a different one. There was no problem exchanging it since there’s no wear when testing it for a few miles. Actually, the old one I removed to begin with showed no wear either.
George Champion

You can get a box of gears to put on the speedo cable.
They are about the size of a match box. Most speedo and hot rod places can sell you one for about $60. One end will be a T5 thread/screw on and the other is an MG thread. You drive the car behind a car with a calibrated speedo (or use a GPS) for a distance. The longer the better. And read the odometer. eg drive 10.0 miles and your MG says 18.42 miles. That gives them an accurate ratio.
Do you have EFI?. Idle should be around 800 or less. The whistling might be the fine idle idle screw set too high.
dial it back and 'adjust' the coarse idle (eg bend the metal tab that rests on the on the throttle lever stop)
Peter Sherman

This thread was discussed between 31/08/2010 and 06/09/2010

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