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Broken head bolts on 346 V8 engine

Started by gary griffin, January 08, 2012, 12:17:40 PM

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gary griffin

I am introducing this post to hopefully help someone avoid the problems I have had. My car ran very well when I bought it and started restoring it. It had 83,000 miles on the Odometer and fairly even compression readings. I have no history on the engine but decided to leave it alone as far as rebuilding it for time and monetary considerations. It also had a bracket appartntly for a missising after market oil filter bolted on the left head with 4 bolts. I decided to clean up the engine compartment and buy an oil filter to install on the left inner fender. My painter has a full service shop so I had him remove the engine to clean up the engine bay and paint it properly and to remove the bracket. He called me when the first bolt broke and I knew I would have to remove all of them to clean out the bolt remains. I took the engine to a rebuilder I have used in the past and he ended up breaking most of the bolts removing the heads. I sent the engine to a machinist (old salty guy with lots of experience) and he removed the stubs by drilling them then heating them to a dull red color and then puting in an easy out, and if that did not work immediatly he drippped some CO2 on the easy out which cooled the bolt stub and removed them when they contracted. In the end I will have a fully rebuilt engine but will be finishing much later than my original schedule.

The bottom line to this long post is that I would recommend tht you never remove head bolts from a 346 V8 unless you really have to.
Gary Griffin

1940 LaSalle 5029 4 door convertible sedan
1942 Cadillac 6719 restoration almost complete?
1957 Cadillac 60-special (Needs a little TLC)
2013 Cadillac XTS daily driver

vicbrincat

#1
Gary I agree with you  100%. You need to think twice before removing the head bolts from a flat head. When I pulled mine off, they did not break but they were badly corroded and pitted. In fact, I'm suprised none snapped off.

The only concern I have is that the manual recommends that you remove certain head bolts for proper engine flushing and cleaning. (I would think twice before I followed this particular manual instruction). In this day and age there are probably better ways to flush and clean your cooling system. Also, the coolants are much better  than the ones we had 65 years ago.)

Vic Brincat

gary griffin

Possibly we could shorten the bolts so they dont (Or barely do) go into the water jackets and then coat the ends with rust inhibitating paint?
Gary Griffin

1940 LaSalle 5029 4 door convertible sedan
1942 Cadillac 6719 restoration almost complete?
1957 Cadillac 60-special (Needs a little TLC)
2013 Cadillac XTS daily driver

vicbrincat

Gary I would be concerned about shortening the bolts, and to be honest with you I really think that painting will not work in the long run. And may infact cause the same issue once the paint hardens. I noticed that some bolts run deeper than others and of course, the ones holding on the heater hose outles are actually longer than teh rest. (You must always be careful to uses these ONLY for teh water outlets.

I seriously doubt that in my lifetime I will ever be in a situation that I would need to remove these headbolts again.(Okay..never say never). My concern would be more for those who have older rebuilds or ones  that have engines that have never been apart.

For those of us who  have laboured to rebuild these monsters, I think the best apporach is a good anti-siezing compund in the threads.

Vic Brincat