[DeTomaso] Cylinder Wall question

[Will Kooiman]

I had the same spots on my block a few years ago.  I thought it was cracked.
When I got the block out, I realized they were stains - very light rust
stains.

There's probably a rule-of-thumb, like if you can catch your fingernail on
them, they're a problem.  If you can't don't worry.

Most likely they aren't a problem, but you need to determine how deep they
are.

Here's a weird question.  Are 351C blocks special in this respect?  Are they
made of a different iron composition that makes them leave rust stains?  I
don't remember seeing these stains on the 302's that I used to run, nor on
the 428CJ that I had.  The 428CJ sat in a barn under a tarp for 10 years.
When I took it apart, there weren't any weird rust marks on it.  The 302's
blew -many- head gaskets.  I'm sure they sat for months at a time with water
residue in the cylinders.  I don't remember seeing any stains whatsoever -
but then, that was a long time ago.

Incidentally, on another 351C block, it had rust spots on the standard
bores.  I had them bored 0.030 due to the taper, but not all of the spots
came out.  Rather than boring until the spots came out, I left a couple of
the pits in the cylinders.  The pits are very small.  I doubt they're going
to cause a problem.

-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of Thomas Borcich
Sent: Friday, August 14, 2009 1:33 PM
To: Pantera REALBIG forum
Subject: [DeTomaso] Cylinder Wall question


Motor experts I need your opinion...my motors out while wheel house repairs
are being done. 
Motor is down to the short block for cam, head, valve train and oil pan
additions. 
I noticed on one of the cylinder walls there are spots that look like water
spots where the metal is discolored. 
There's no rust on the surface and the surface is smooth....just these
"water like" spots where the metal is slightly darker. 
I took some 200 grit sand paper and hit the spots very lightly to see if
they would lighten up and they did.
The motor was bored .030 over in 2003 reassembled and was only driven from
the shop to the previous owners
house and sat until I bought it. There's less than 20 miles on this motor.
The cylinders still show pretty 
fresh hone marks. Also in the bottom of the same cylinder bore when the
piston is at the bottom of its stroke there is an 
uneven line about 1/2" above the piston, that gives me the idea that it
might have been created by a little 
water sitting in the bottom of the cylinder at one point in its life. Not
sure if it was before or after the rebuild?

Since the block was bored by the previous owner (pistons are marked .030
over), maybe there was a problem 
at that time which necesitated the boring and they didn't want to go any
farther on the bore?  My biggest
concern is the clevelands are known for thin walls and it may have pin holes
that are seeping now.

Any idea what these spots could be?

Best regards,



Tom 
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