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Re: U20 block and crank question

To: Davesmbox@aol.com, datsun-roadsters@autox.team.net
Subject: Re: U20 block and crank question
From: Perry Smith <tpsmithstl@yahoo.com>
Date: Fri, 12 May 2006 06:09:20 -0700 (PDT)
Dave,
   
  When I had my U20 rebuilt three years ago the machine shop told me my crank 
was scored (it was).  I had taken it apart before bringing it to them for the 
rebuild so I knew that was true.  It was scored because the PO had oil-starved 
it (at least once) and the reason it needed the rebuild was because of this oil 
starvation - and that had caused one of the main bearings to break loose from 
excessive wear. I had no doubt the crank needed to be either replaced or 
"built-up".  There was no scoring on the journals.  My brother is a mechanic 
and told me that since the crank on a U20 is forged and not cast, it can easily 
be built-up by welding (and is worth it!).  (Side note: if you ever have the 
crank out and lightly tap it with a wrench it makes the nicest "ting!" - just 
like a bell, you'd ever want to hear.)  Since there was no other reason to go 
oversized bearing or rings, etc., I opted to have the crank built-up.  So far 
no problems and I still have this nice "real" racing
 engine - eyelashed valve cutouts, etc.  My brother also told he the history of 
the engine (U20)was that it was a Mercedes-Benz inspired/designed/licensed 
engine.  I don't know if that's true, but it's an interesting piece of history 
for a car that has lots of influences from other cars of that era.  ANone know 
if that's true?
   
  I opted to keep as close to "original" as possible - I'll do oversized 
bearing later, if necessary. I sometimes like to think of my Roadster as a 
"well-built" MG, if there is such a thing...ha, ha!  Of course my fiance just 
calls it my "Stuart Little" car and leaves it at that.
   
  Perry Smith
  '68 2000

Davesmbox@aol.com wrote:
  We have a roadster new comer here in Ma. The machine shop told him his U20 
block and crank were no good.
I gave him a spare block and crank I had with the understanding that he pay 
me what its worth when he is done with the rebuild.
Here is the problem. They told him my crank was no good and has to be built 
up with welding and recut. I thought that was a technique reserved for cranks 
which oversized bearings are not available or large 18 wheel truck cranks 
with a million miles on them. As far as I know this crank hasn't been 
previously 
cut so it should be machinable to fit an oversized bearing. Are we missing 
something or are we getting bad advice from the shop????.
The block. One piston was frozen and had to be driven out. They told him 
the block needs to be SLEEVED and he still needs oversized pistons. Ok as an 
old 
Triumph owner (that used a sleeved engine) I thought the main reason an 
engine was sleeved was make the sleeve and piston changeable OR if oversized 
pistons were not available. But why bore in a sleeve AND still need oversized 
pistons????? Are sleeves even out there for the U20???

Is this machine shop just giving us some bad advice?

Thanks for any input,
DAVE



                
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