well... depending on exactly where the crack is...
if the crack is in the cylinder itself... then it's an easy fix... have your
machine shop put a sleeve in it... it's easy to do... any competent machine
shop that has the ability to bore cylinders can do it... and i am quite
positive that you can get a 'nylen' or 'la sleeve' liner for it... perhaps
not by application but by dimensions for sure.
this is can also be done to a block that has been overbored multiple times
to get it back to standard bore dimensions... not worth doing to your chevy
350 block... but on something such as a roadster block... that are getting
harder to come by... worth the effort
i have done this to many blocks and have had NO troubles with it... the
important thing is that it is done properly... for it to work properly and
not leak... actually... i have also done this to blocks that i sonic checked
and had thin cylinders... (less than .100 inch on thrust side)... just use a
.125 wall sleeve with a finished internal diameter the same as the bore i
wish to go with... bore the block to .002 inch less the outside diameter of
the sleeve (for press)... press it in... surface the deck... finish bore and
hone the cylinder... and... good as... if not better than new.
now... if the crack is elsewhere... depending on where... and how bad... it
is possible to "pin" it... using small tapered threaded pins... this works
well... but is often a real pain on large cracks... therefore... expensive
on larger cracks.
welding is the last thing i would attempt... cracks often times appear
elsewhere if not done correctly (using an oven... etc...)
so... it should not be any problem for a competent machine shop to fix.
hope this helps.
j.bostick
----- Original Message -----
From: <JOHNSOF@aol.com>
To: <datsun-roadsters@autox.team.net>
Sent: Wednesday, May 02, 2001 10:24 AM
Subject: HELP! Need U-20 Block!
> Bad news from the restoration front...we have found a large crack in the
> bottom jackshaft side of #3 cylinder bore. There has been some polishing
> done around the crack, so between this and the interesting things done to
the
> cylinder head it's clearly an engine that was blown up sometime in the
past
> and reassembled just to sell it.
>
> Does anybody have a good block THAT THEY DON'T NEED? I have new Datsun
> 1st-over bearings, pistons, rings, etc. so I would love to find a block
that
> is standard. I don't need anything but the bare block (although if it's
> easier I can take the block apart), and as I'm alreay spending a ton
> rebuilding the head I don't want a questionable block - I'm willing to
bake
> it out, magnaflux it, etc. etc. etc. and spend the money to machine it
> properly, but I want a good starting point.
>
> I asked the machinist about welding the crack, and of course welding cast
> iron is difficult but doable (and expensive). There's concern about the
> crack propagating up to the water jacket. Any opinions?
>
> And yes, I will be talking to the vendors - I just thought I would check
with
> the list in case there's someone around who has one they absolutely don't
> need.
>
> I will be traveling on business to AZ next week and UT the following week,
if
> that matters to anyone. I could conceivably go to CA and pick up a block
if
> I had to; of course I'd rather build a box and ship it, but...
>
> Thanks you for any help or advice you might have.
> Fred Johnson
> '69 SRL (now with even more pieces that before!)
> Wisconsin
>
> By the way, the cylinder head is from a 67.5 (no air injectors) and the
> bottom of the head was planed .020". This undoubtedly created some
binding
> of the camshaft, so THEY PLANED OFF THE BOTTOMS OF THE CAM TOWERS TO MAKE
IT
> FLAT! No wonder the timing chain was loose! BEAT THAT FOR A G*$%)@M
STUPID
> PO STORY!
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