Anticipating trouble...'88 Supra BHG

[Hachiroku $B%O%A%m%/(B]

Again, the 1988 Supra. I mentioned checking the head bolt torque when I
had the valve covers off, and I remembered something.

Like GB said, the leak usually occurs around cylinder #6. I remember
reading something about the head being so large and the heating/cooling
that happens is uneven, so the head 'walks' as it's cooling down.

Checking the torque, one of the last head bolts on the passenger's side of
the car hit ~66 ft/lbs and just seemed to keep turning...

I am anticipating doing some sort of repair on this thread, most likely a
Heli-Coil. I used to use these at one place where I was working, but that
was a long, long time ago with bolts that measured ~3-4mm.

What else do I need to know about this?

 

[Gary L Burnore]

Again, the 1988 Supra. I mentioned checking the head bolt torque when I
had the valve covers off, and I remembered something.

Like GB said, the leak usually occurs around cylinder #6. I remember
reading something about the head being so large and the heating/cooling
that happens is uneven, so the head 'walks' as it's cooling down.

Checking the torque, one of the last head bolts on the passenger's side of
the car hit ~66 ft/lbs and just seemed to keep turning...

I am anticipating doing some sort of repair on this thread, most likely a
Heli-Coil. I used to use these at one place where I was working, but that
was a long, long time ago with bolts that measured ~3-4mm.

What else do I need to know about this?

Buy another engine.

--
(e-mail address removed)
----------------------------------------------------------------------
How you look depends on where you go.
----------------------------------------------------------------------
| ÝÛ³ºÝ³Þ³ºÝ³ÝÛ³ºÝ³Þ³ºÝ³Ý³Þ³ºÝ³ÝÝÛ³
Gary L. Burnore | ÝÛ³ºÝ³Þ³ºÝ³ÝÛ³ºÝ³Þ³ºÝ³Ý³Þ³ºÝ³ÝÝÛ³
| ÝÛ³ºÝ³Þ³ºÝ³ÝÛ³ºÝ³Þ³ºÝ³Ý³Þ³ºÝ³ÝÝÛ³
Black Helicopter Repair Services | ÝÛ³ 3 4 1 4 2 ݳ޳ 6 9 0 6 9 ÝÛ³
| Official Proof of Purchase
======================================================================

 

[Nate Nagel]

Buy another engine.

Bah. forget that noise, a Helicoil ain't rocket surgery. So long as
you have a drill with enough cojones, a 12mm Helicoil is no more
difficult to insert than a 5mm one (where do you find 3mm Helicoils? I
needed to mail-order 5mm ones to repair a rack mount hole in the rear
dropout of my bicycle...) Remember, a drill bit self centers to an
existing hole, so as long as the threads stripped cleanly and evenly,
your only real concern is getting the Helicoil all the way in. (since
I'm assuming that this is a blind hole, and you really don't want to
drill it any deeper than it already is, for fear of breaking through to
a water or oil passage, you may need to take the Helicoil tap and after
tapping until it hits the bottom of the hole then cut the end off with a
cutting wheel to make a "bottom tap" and then have another go at it. In
an emergency when the only Helicoil I had was too long and I'd already
inserted it in the hole, I have dressed the end of it with a flat file,
but I would be hesitant to do that on a head bolt. I would carefully
measure depth first, then modify the Helicoil as necessary before
inserting. I seriously doubt that you will have THAT problem, however.)

I would, however, replace at least that one bolt, and check with someone
familiar with your engine if a Helicoil can successfully be inserted in
that particular hole. Sometimes there just isn't enough meat in that
area of the block so that inserting a Helicoil will significantly thin
the structural metal in that area - in that case the solution is usually
a Timesert. (I know that the Timesert is the preferred solution for
pulled head studs on a Porsche flat-six; I assume that it is for this
reason.)

I would of course use a good straightedge and feeler gauge to check for
warpage/unevenness of both the block and head surfaces before calling it
soup and reassembling.

nate

 

[jim beam]

Buy another engine.

concur. /much/ cheaper.

 

[Nate Nagel]

Bah. forget that noise, a Helicoil ain't rocket surgery. So long as you
have a drill with enough cojones, a 12mm Helicoil is no more difficult
to insert than a 5mm one (where do you find 3mm Helicoils? I needed to
mail-order 5mm ones to repair a rack mount hole in the rear dropout of
my bicycle...) Remember, a drill bit self centers to an existing hole,
so as long as the threads stripped cleanly and evenly, your only real
concern is getting the Helicoil all the way in. (since I'm assuming that
this is a blind hole, and you really don't want to drill it any deeper
than it already is, for fear of breaking through to a water or oil
passage, you may need to take the Helicoil tap and after tapping until
it hits the bottom of the hole then cut the end off with a cutting wheel
to make a "bottom tap" and then have another go at it. In an emergency
when the only Helicoil I had was too long and I'd already inserted it in
the hole, I have dressed the end of it with a flat file, but I would be
hesitant to do that on a head bolt. I would carefully measure depth
first, then modify the Helicoil as necessary before inserting. I
seriously doubt that you will have THAT problem, however.)

I would, however, replace at least that one bolt, and check with someone
familiar with your engine if a Helicoil can successfully be inserted in
that particular hole. Sometimes there just isn't enough meat in that
area of the block so that inserting a Helicoil will significantly thin
the structural metal in that area - in that case the solution is usually
a Timesert. (I know that the Timesert is the preferred solution for
pulled head studs on a Porsche flat-six; I assume that it is for this
reason.)

I would of course use a good straightedge and feeler gauge to check for
warpage/unevenness of both the block and head surfaces before calling it
soup and reassembling.

nate

Forgot to mention... when checking block with a straight edge, you may
discover high spots immediately around the bolt holes. You'll want to
knock those down by chamfering with a larger drill bit, and/or with a
flat file if they'd require a huge chamfer (but chamfer would be preferred)

nate

 

[clare]

Bah. forget that noise, a Helicoil ain't rocket surgery. So long as
you have a drill with enough cojones, a 12mm Helicoil is no more
difficult to insert than a 5mm one (where do you find 3mm Helicoils? I
needed to mail-order 5mm ones to repair a rack mount hole in the rear
dropout of my bicycle...) Remember, a drill bit self centers to an
existing hole, so as long as the threads stripped cleanly and evenly,
your only real concern is getting the Helicoil all the way in. (since
I'm assuming that this is a blind hole, and you really don't want to
drill it any deeper than it already is, for fear of breaking through to
a water or oil passage, you may need to take the Helicoil tap and after
tapping until it hits the bottom of the hole then cut the end off with a
cutting wheel to make a "bottom tap" and then have another go at it. In
an emergency when the only Helicoil I had was too long and I'd already
inserted it in the hole, I have dressed the end of it with a flat file,
but I would be hesitant to do that on a head bolt. I would carefully
measure depth first, then modify the Helicoil as necessary before
inserting. I seriously doubt that you will have THAT problem, however.)

I would, however, replace at least that one bolt, and check with someone
familiar with your engine if a Helicoil can successfully be inserted in
that particular hole. Sometimes there just isn't enough meat in that
area of the block so that inserting a Helicoil will significantly thin
the structural metal in that area - in that case the solution is usually
a Timesert. (I know that the Timesert is the preferred solution for
pulled head studs on a Porsche flat-six; I assume that it is for this
reason.)

I would of course use a good straightedge and feeler gauge to check for
warpage/unevenness of both the block and head surfaces before calling it
soup and reassembling.

nate

Time-sert and Helicoil require virtually the same amouint of space -
but the 'sert makes a nicer job.