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Wrench holding on exhaust manifold

don4331

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Studs are used for 2 reasons:
1. Is for assembly - As the 3.0 was used in several different vehicles, and each needs a different set of exhaust manifolds, the engine plant couldn't bolt manifold to head before head is bolted to block. So, when it came time to install exhaust manifold on assembly line, it is tremendously faster to slide exhaust gasket on studs, slap the exhaust manifold on, spin a couple nuts on, and torque to spec than to try to line up manifold & gasket on head, then thread a bolt into the hole in the block (at least for 1st 2) and then torque down.​
2. When you tighten a bolt, the shaft of bolt twists as you tighten. So, the torque on the threads isn't the same as what your wrench shows. On the other hand, there is very little twisting within a nut on a stud, to the torque on the wrench matches. Therefore, studs give much more accurate measurement. If you are building an F1 engine, you use studs not bolts.​
Do you need that assembly assistance/precision in tightening? Probably not, so a bolt will work fine. You need to be careful that the bolt is not bottoming out at end of threaded portion, before it pulls tight or you won't properly tighten the manifold to the head.​
Threads are probably in rough shape - heat and moisture will have accelerated rust in holes - that's part of why they are so difficult to remove. You can pick up a cheap tap for $5 and clean hole up in couple minutes.​
As fewer than 1 in 100k Rangers every had to have exhaust manifolds removed under warranty, why would Ford spend more for individuals having issues 20+ years later (they would much sooner you bought a new Maverick). Enter comment about disposable society we live in.​
 


James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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There are two trucks. Both are sorted. Probably selling the '99.
I can't get the tap to take in the threads. It seems like it goes partway through the block flange kind of loose then there's still some threads supposedly but I'm having no progress. When I stick a wire in there it goes through but there must be something f'ed up. I can try to get some undersize drills through. If I have a clear hole I can run a slightly undersize bolt through and put a nut on the back of it and just not use the threads in the block flange.

It's always something.
 

James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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My credo
There are two trucks. Both are sorted. Probably selling the '99.
I can get 6.4mm drill thru. I was going to sneak up a little bigger by .1mm but can't get electric drill in there and drill bit is too big for small tap wrench and too small for large one.
Since I have 1/4" of hole I'm thinking of just running a 1/4" bolt thru with a nut on the back. That's better than nothing.
I think the main problem is the metal of the flange is really hard. So I was thinking if I drilled it out but leaving enough for at least some threads I might be able to tap it, but at this point I'm wondering if it's worth it.
 

Roert42

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I would have no issue leaving a bolt with nut on it. Use a lock washer or double nut to keep it from rattling loose. Call it done.
 

don4331

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If you have 6.4mm drill through, the threads are gone; put a bolt in it (with nut & lock washer) and call it a day.
 

James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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235/75-15
My credo
There are two trucks. Both are sorted. Probably selling the '99.
I put a 1/4" threaded rod though it with nuts then the oil dipstick holder over that with a nut.
It's not as good as OEM but I'm calling it done at least for now.
On to next broken thing.
 

James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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4.0L in XLT, 3.0L in B3000
Transmission
Automatic
2WD / 4WD
4WD
Tire Size
235/75-15
My credo
There are two trucks. Both are sorted. Probably selling the '99.
well threads aren't totally gone or I'd be able to slip the tap thru it. There's actually quite a diff between 6.4 and 7.8 or whatever the 8mm threads are at their largest. Whatever the diff is, I can't cut into it... so... the 1/4" rod, it works, and from all the likes, seems acceptable.
if it leaks it'll be noticeable, so far, no problem.
if you look at what is thread high and low diameters for 8mm I think you'll find both are larger than 6.4. Not to quibble. If the 1/4" is in there and seems secure, I think it's ok, looks ok, and I think the chance someone would say it's not OEM so doesn't pass inspection is about zero. The rule is, no exhaust leaks, not, how it's put together. I think.
 

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