From digest.v7.n341 Sat Sep 27 09:34:55 1997
Date: Fri, 26 Sep 1997 23:57:34 -0400 (EDT)
Subject: <small sixes>re: Ambrose Raftis Head Crack Q??
Modem crapped out while sending this first time so if it comes across twice,
Small six heads are prone to cracking.
Before we bought my wife's 528e, it had also experienced a cracked head;
replaced to the tune of about $2,000, as I recall.
Dave Cruse (Engine Specialties, Tracy, Ca) is building a new engine for my
323i. He encouraged me to start with a new head blank because of the failure
rate on the small six heads. They seem to all stress and crack just in front
of, and parrallel, to the second cam tower on the left (I think) side. Since
my head is fine right now (the one in the car atleast), I couldn't justify
the 1,200 bucks for a new (also perfectly fine) head blank.
While I was out at his shop, Dave pulled out about half dozen small six
heads, each cracked along the same exact line. We noted how the head designs
had gotten progressively beefier on the newer (but cracked) heads, much more
metal around the base of the cam towers, but still, there they were in the
cracked head heep. Again, each had cracked in the same exact place.
Dave had once built up the metal around the cam tower in question on an older
head; it eventually cracked at the same place on the opposite side. In my
case, I had him build up the second cam towers on both sides. No guarantees,
I'll see how it plays out.
I think Dave has experimented with repairing these cracked heads, and may
even have some reconditioned replacements for sale. In any case, my only
affiliation with Dave and his machine shop is that I've entrusted him with
the rebuild of my engine because I believe in his work. As they say, YMMV.
As an after thought, I'm wondering....small sixes stress and break hardened
(hex style) head bolts. Small sixes with strethchy (torx) bolts don't break
bolts. Could there be a correlation: use stretchy head bolts, get less
stress, less metal fatigue, maybe no more cracked heads because of the
forgiving headbolts? What do the engineers out there say?
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