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MG MGB Technical - No power top end

I have just completed restoration on a 1975 MGB but it does not seem to have any power. It will rev fine at slow speed but tops out at about 60 miles per hour at about 3000 rpm. Also going up hill modest grade the car will slow to the point I must down shift.
I have cleaned and over hauled the carb Zenith 175 cd and it has been set prpoerly, it has a 45d4 distributor with an eletronic module fitted. I have replaced the fuel filter , fuel pump and fuel tank and pickup and can not find any vacuum leaks . The car starts and runs great except at highway load on the engine no missing or back fire just runs out of power. Valves are adjusted and the compression is good. this car set for about 6 years with out being started. Any help or ideas would be appriciated. thank you
A. Todd

Is the mechanical advance working properly?
The most likely cause of your problem is
insufficient advance. I think your should
have 10 deg at 1500 RPM, but if you have an
advance timing light, you can make sure you
have the correct maximum advance.

Check out www.mgbmga.com for distributor timing
data.

Are you using the stock cam? The aftermarket
cams may need to be "dialed in".

Are you sure the throttle cable is adjusted
properly?

Finally, I have a 79 with the Zenith also,
and its hard to go over 75MPH, so don't expect
miracles since the manifold is so restrictive.
Ronald

Check the pump is delivering at least one Imperial pint per minute at the carb.
Paul Hunt

Did you say that the engine was rebuilt?
If there was a new timing chain installed, then perhaps the cam timing was done incorrectly?
Personally, even I [the expurt] have made this mistake. [blush]
Also had a lucas breakerless system in my '77 with the same symptoms. Just wouldn't rev. to anything over 3500 rpm.
Safety Fast
Dwight
Dwight McCullough

The first and easiest thing to do is check the fuel pump as Paul advised. New parts don't function properly more often than you might think.

The fuel delivery problem manifests itself exactly as you have described.
Fred Horstmeyer

Make sure the body of the condenser in the distributor is securely screwed on. As they come loose they vibrate and the top end power shuts off lower and lower until they a) fall off b) the screw drops into the body of the distributor (issuing a sound similar to "Graunch, Oh s**t")
M S Akehurst

May sound silly, but the 175 sometimes won't work at top end without the air cleaner installed.

Mike
Mike Phillips

This thread was discussed between 20/07/2003 and 22/07/2003

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