TR water pump seal

Well, the reason that the seal did not fit well was that you installed the wrong part. Testarossa's with engine numbers 20820 and lower originally used a two piece seal #120948. This was superseded to a one piece seal #152051. This one piece seal is a direct replacement with no modifications required, and is the seal that you should have installed.
TR's with engine #20821 and higher used the seal that you installed #183759. The later waterpump has a different length shaft, a different sized seal spacer and a different impeller.
You should have done more research before modifying your impeller, as there are multiple threads on this very topic. I hope that your modified impeller works, because taking the engine out if it leaks is a lot of work. You might consider pressure testing the seal as shown in the workshop manual before installing the engine.
It only requires making some plugs and adapters for the coolant hoses.

Whoever sold you that seal should not be selling parts for a living.

 

thank you brian for the explanation
but I prefer what david was doing
the new 1 piece seal 152051 cost at ricambi america 137.38 $, the seal for newer engines (183759) only 33,80 $
and to modify the impeller is about 15 minutes work maximum

and if david will check before installing the engine for leaks and all would be ok then this is a good alternative

 

I have never advocated that modification. In cars requiring the later seal I use it. In cars requiring the early seal I use a different one. There are many available.

 

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183759 is the revised 512TR part.

I know an upgrade aluminum impeller exists for early cars. Is there one that likewise exists for cars that originally used 183759?

 

Last time I did this, I noticed my late 91 Euro spec car was equipped with an early seal. The engine is original to the car.

No idea how this happened, but it gets frustrating ordering the wrong part every 5 years or so because you forget. As a byproduct, I now have a nice supply of new water pump seals that don't fit.

Now I just leave the thing alone if it is not leaking.

 

I would never refer to an aluminum impeller to an upgrade over a brass part. Aluminum impellers industry wide have a reputation for various failures.

I'll keep my yellow one.

I have enlarged the recess of dozens of impellers to install the one piece seals.

 

I thought the 512TR used a plastic impeller. If brass agree !