Re: IHC Engine Durability

[jlandry@domain.elided (John A. Landry)]

In Linda Tripp's secret telephone recording, Monica and "CDesPlanques"
<adesp@domain.elided> were heard saying...

>The "crack" is
>between the spark plug hole and the intake valve.  I think it had to be in
>there when I got it, and the heating and cooling flexed it enough to
>surface........I'd think the heavier duty / more metal block would be less
>prone to warping, but like I said he's the expert - ha.  Any Ideas,

Chris,

I've recently done a little research on cracking found (from time to time) on
V392 heads.  In the 392 I just finished rebuilding, I initially wasn't
planning on having the heads magnafluxed.  But after hearing repeated first
hand tales of cracks being discovered by other rebuilding their engines, I
changed my mind and started worrying about it.  Luckily my heads turned out
fine... the price of the magnafluxing was cheap peace of mind.

Anyway, I've pretty much learned that cracking in the 392 heads generally
happens between the spark plug and the exhaust valve seat pocket.  Sometimes
the hardened valve seat insert will not crack itself.  Of course this same
cracking could occur in other size heads as well (maybe to a lesser degree)
and from the spark plug hole to the intake valve pocket.  Unfortunately
there's a water passageway the runs between the two valve pockets, so if a
crack intersects this, a coolant leak might occur.  The respected machine shop
I just worked with told me that simply finding a crack in an IH head doesn't
automatically mean the head is toast.  They have successfully welded up these
cracks and put the heads back in service.

As to what causes the crack... common sense tells me a warped block is utter
BS.  That hunk of IH iron is one of the biggest, thickest, heaviest blocks
I've ever seen and I doubt they warp very easily.  More likely the common
cracks found in the heads are caused by severe thermal expansion and
retraction events due to episodes of overheating.  No proof... just my guess.

Take care,

John L.
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