I think it's just random. I have torn down a few motors and haven't noticed any pattern. Some bolts break, thats why we do our best to soak them with penetrating oil.

I would think that the older motors would be more prone to break with age/metal characteristics coming into play.

 

This little tool is getting a workout latley removing broken bolts, does a nice job.

The QuikCenter Tool

 

1991 was 22 years ago. See where this is going? When I had my 53 Chevy truck, it was 32 years old and to have a bolt *not* snap off was the exception. Exhaust bolts see the worst duty; large swing temperature cycles. My 86 Toyota pickup usually looses one or two of the studs or nuts if I have to remove them. Always a good idea to replace those with new just because they have such a hard life.

 

The issue is failure due to weakening by corrosion (and to a lesser extent combined with over torquing) and has been around since long before the 1990s (I know). Valve cover bolts usually dont see too much corrosion but the intake manifold bolts at the 4 corner positions and especially the front 2 see alot of corrosion due to weeping/leaking coolant from the coolant passages there. Same for water pump/front cover fasteners.

Your best defense against these types of failures is to use quality stainless steel (ie 304) fasteners, clean and chase all threaded holes, or use anti seize, etc, if needed, and follow all factory fastener torques specs (noting that the use off any fastener lubricant - such as anti seize - will require an adjustment to the actual torque applied to achieve the required clamping pre-load).

Paul

 

The three newer engines I mentioned above all appeared to be factory, nobody had taken them apart before so they probably were all at factory torque spec's etc...

I also have taken apart countless older 289/302/351W's and have not encountered this bolt snapping issue. Comparing the newer Ford bolts to the same application older Ford bolts, they look and feel different, quality does not appear to be the same.

Any tricks to keep this from happening as I take bolts off newer engines other than what I'm already doing by using PB Blaster to soak the bolts before I try to remove them? Does heating with a torch help much?

 

I had the same problem with the front intake bolts on a 95 and a 96 Windsor (roller) motors. The "old" motors usually leaked so much oil around the intake gasket that those bolts were lubricated and didn't break off. I broke 3 out of 4of the front intake bolts. The bolts are thru holes so next time I get a motor I will turn it upside down and soak the holes with PB blaster. I tried the heat trick and didn't seem to help.

 

Sorry to hear you had a similar experience, makes me feel a little better knowing it's not just me.

 

the only bolts that usually break on me are the water pump bolts on the newer 302/351's.

 

Yep, had that happen too! Very frustrating when a simple job gets complicated by a broken off bolt!

 

Not the least part of the problems being discussed here is the cost cutting
programs Ford and the other domestic assemblers embarked on starting in the late 80s. Ford, and the other mfrs. purchase fasteners from manufacturers and distributors. The QC efforts are somewhat more stringent for direct suppliers,
such as the company I represented, than for distributors, who, quite often
purchase fasteners from countries outside the US. Many times these fasteners are
used as ballast for container ships laden with above deck cargo containers.
Almost all "standard" fasteners enter the USA this way and are usually sold by the
pound to bidders who repackage and sell them in ACO, Home Depot, etc.
The blister packaging is usually way more expensive than the actual fastener inside.
As these fasteners are used in non critical applications, fine, they are usually
dead soft with pretty plating, NOT SAFE for any critical application.
Distributors also purchase automobile fasteners that are certified as to hardness, yield
and tensile strength. Since The big Three did away with incoming inspection of
supplier parts in the late 80s, I will let your imagination decide as to how many
non-conforming parts made their way onto and into our vehicles.
One of the major differences in domestic and foreign vehicles is the foreign
manufacturers own almost their entire supply network. This has changed as
more transplant plants are operating in the US, but the Hondas and BMWs
still randomly check parts to assure quality. Probably the most eggregious example of what a disaster this can be is the "phony grade 8" incident that occured in
1989-1990. Many of these fasteners found their way into military vehicles and
aircraft. Entire lots, tons of fasteners,were discarded as there is no way to tell a fake
Grade 8 from a geniune one, the head markings are identical. Most test methods
for tensile and yield are destructive. Only Rockwell hardness coud be tested.
All the phony grade 8s were traced eventually to offshore manufacturers.
We live in a world that, sadly, places profit above everything else.

 

That doesn't surprise me that it came down to money, cheaper bolts means less cost when building the engine new! So frustrating!!!