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From: owner-80-96-list-digest ford-trucks.com (80-96-list-digest)
To: 80-96-list-digest ford-trucks.com
Subject: 80-96-list-digest V3 #366
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80-96-list-digest Monday, December 27 1999 Volume 03 : Number 366



=======================================================================
Ford Truck Enthusiasts - 1980-1996 Trucks and Vans
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In this issue:

Re: FTE 80-96 - Exhausted Manifolds
Re: FTE 80-96 - Exhausted Manifolds

=======================================================================

----------------------------------------------------------------------

Date: Sun, 26 Dec 1999 22:24:55 -0600
From: "Shawn & Jennifer Clark" tyler.net>
Subject: Re: FTE 80-96 - Exhausted Manifolds

Blake wrote:
>>I know these newer engines run a lot leaner than in the 70s, so I suppose
that could make the manifolds run hotter. But Ford has been building a lot
of different engines over the last 100 years, so they should know how to
make manifolds that hold up to what their engines do.
<<

Perhaps, but my '91 and many others are cracked. I question a couple of
things with the manifold's design, but the culprit may be something
else--materials, water splashing on it while hot, improper torquing during
assembly, one cylinder running hot, etc. There are significant thermal
expansion issues in the exhaust that can be kind of subtle. If I recall
correctly, some Honda's had a problem with cracking exhaust manifolds a few
years back due to improper design of the exhaust system mounting, but they
had a TSB that fixed it pretty rapidly. My pet theory about my manifold is
the way the exhaust system and cat hang off of the manifold leads to a
crack. I'm not a mechanical engineer, but the cantilever weight hanging
from it might crack it after XXXXX number of vibrations. Mine cracked
right where the stresses from this cantilever should be highest. Also, I
have not pulled it off yet, but I'm told there is no gasket. If there were
a gasket it might allow a little bit of flexure that would reduce the
stress on the manifold a little--maybe just enough to prevent the crack
from starting. This is just a wild assed guess. Some other ideas I have
heard here seem just as plausible. I don't know precisely what is wrong
with it, but I agree that after 100 years Ford should know how to design
manifolds that don't crack like this. However, in any company, people
eventually move on, and some of the hard lessons they have learned are
lost...only to be rediscovered by some poor soul later on (been there, done
that.) Then there are the more frustrating possibilities like: the
original design intent required a better alloy, but someone on the project
got pressed to save a few bucks late in the project by the bean counters,
so he/she decided cheaper material should work, but with a few more
failures.

I'll resist listing off the many other things that they should know how to
make properly, but didn't on my '91. Did someone say paint? OOPS, it
just slipped out (or did it peel off?) Plastic power window gear sets?
OOPS, another one. How 'bout those "better idea" AC fittings? I better
stop, I'm just getting warmed up here.

Shawn Clark







== FTE: Uns*bscribe and posting info http://www.ford-trucks.com/faq.html

------------------------------

Date: Sun, 26 Dec 1999 21:10:11 -0800
From: "Dave Dodds" home.com>
Subject: Re: FTE 80-96 - Exhausted Manifolds

Does anyone out there have experience with the "Aerostar", the
"Fold-a-cover" or the "Scott-top" lines of box covers that feature
alternatives to the forward hinged box cover? just bought my truck and want
to cover and secure the bed.

Thanks,

Dave Dodds
- ----- Original Message -----
From: Shawn & Jennifer Clark tyler.net>
To: <80-96-list ford-trucks.com>
Sent: Sunday, December 26, 1999 8:24 PM
Subject: Re: FTE 80-96 - Exhausted Manifolds


>
> Blake wrote:
> >>I know these newer engines run a lot leaner than in the 70s, so I
suppose
> that could make the manifolds run hotter. But Ford has been building a lot
> of different engines over the last 100 years, so they should know how to
> make manifolds that hold up to what their engines do.
> <<
>
> Perhaps, but my '91 and many others are cracked. I question a couple of
> things with the manifold's design, but the culprit may be something
> else--materials, water splashing on it while hot, improper torquing during
> assembly, one cylinder running hot, etc. There are significant thermal
> expansion issues in the exhaust that can be kind of subtle. If I recall
> correctly, some Honda's had a problem with cracking exhaust manifolds a
few
> years back due to improper design of the exhaust system mounting, but they
> had a TSB that fixed it pretty rapidly. My pet theory about my manifold
is
> the way the exhaust system and cat hang off of the manifold leads to a
> crack. I'm not a mechanical engineer, but the cantilever weight hanging
> from it might crack it after XXXXX number of vibrations. Mine cracked
> right where the stresses from this cantilever should be highest. Also, I
> have not pulled it off yet, but I'm told there is no gasket. If there
were
> a gasket it might allow a little bit of flexure that would reduce the
> stress on the manifold a little--maybe just enough to prevent the crack
> from starting. This is just a wild assed guess. Some other ideas I have
> heard here seem just as plausible. I don't know precisely what is wrong
> with it, but I agree that after 100 years Ford should know how to design
> manifolds that don't crack like this. However, in any company, people
> eventually move on, and some of the hard lessons they have learned are
> lost...only to be rediscovered by some poor soul later on (been there,
done
> that.) Then there are the more frustrating possibilities like: the
> original design intent required a better alloy, but someone on the project
> got pressed to save a few bucks late in the project by the bean counters,
> so he/she decided cheaper material should work, but with a few more
> failures.
>
> I'll resist listing off the many other things that they should know how to
> make properly, but didn't on my '91. Did someone say paint? OOPS, it
> just slipped out (or did it peel off?) Plastic power window gear sets?
> OOPS, another one. How 'bout those "better idea" AC fittings? I better
> stop, I'm just getting warmed up here.
>
> Shawn Clark
>
>
>
>
>
>
>
> == FTE: Uns*bscribe and posting info http://www.ford-trucks.com/faq.html

== FTE: Uns*bscribe and posting info http://www.ford-trucks.com/faq.html

------------------------------

End of 80-96-list-digest V3 #366
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