> >>the truck. Check both the head and block for flatness in several
> >>directions, and pay special attention to the surfaces around
> where the leak
> >>was, make sure there's no low spot.
> >>
> Could someone elaborate on how to check for flatness? And what kind of
> tolerance is allowable?
>
> I'm pretty sure an experienced (machinist, mechanic, ...) , with a good
> straightedge could do this by eye. But I'm imagining myself in this
> position and being a novice, I suspect I'd screw it up. Without the
> experienced eye, what tool(s) would be used to measure this?
I'm strictly a shade-tree mechanic, I'm sure there are better methods. What
I use is a straight edge and a feeler gage. For an overall check, Hold the
straight edge firmly against the surface to be checked, and try to slide a
.002" feeler gage between it and the surface all along the edge. On a 4-cyl
head, I'd do this in 7 or 8 places, boxing in each combustion chamber and
then once again outside the pushrod holes (if present). For a local check,
like where the gasket blew before, hold the straight edge firmly against the
surface, and shine a light through from the other side. If you can see a
local deviation, it's too big, IMO.
My straight edge is a carpenter's square that I know now is straight from
having compared it to freshly-milled heads. But I didn't know that to begin
with, so I just double-checked as much as I could (making the same
measurement using a different section of straightedge and getting the same
result); plus if I thought I had a problem I got the surface milled. The
machine shop agreed that my first warped head really was warped, so I guess
I got it right. A tool and die type machine shop would likely have a
surface plate they could check it against for you (for a price), but I
didn't do that.
Randall
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