88 2.9L Exh Manf. Bolts ???

[Caps4x4]

Well, Time for a new project....


Got, what I hope is, an easy question... I need the bolt dims for the Exh manifolds. Replacing the heads, and after much work, and swearing, ended up having to snap the old ones to get the manifolds off the heads. I'm replacing them with new heads, so it isn't much of an issue.. Except I don't know what sized hardware to replace them with, when I reassemble.

All help is appreciated....

 

[AllanD]

The factory bolts to hold the manifolds to the heads are 8 x 1.25mm metric.
Don't know the lengths, as there are several lengths.

Frankly I make it a practice to helicoil all the manifold flange bolt holes and use hardened "grade 8 bolts" the grade 8 bolts are NOT about "strength"
but about not galling against the 18-8 stainless steel helicoils.

On my personal engines I use ENGLISH threads 5/16-18 to be specific, because
the standard metric lengths "Bracket" the length you need to the Factory cast
manifolds

on the 4.0 and 2.9 the four or five long bolts are available in lengths
that are either 5mm too long or 5mm too short. the 5/16" bolts are
the correct length.

Now the bolts that hold the Y-pipe to the manifolds are 12 x 1.75 thread, again I don't recall the length, but they need to be a reduced size head.

the standard size head for these will (Depending on suplier) either
be 18mm or 19mm and the way the bolt heads "tuck" into the collar
on the Y-pipe you won't be able to get a scket on them.

Personally I recommend to people that they rob a couple of top bellhousing
bolts off of a 3.0 taurus and either shorten them (and cut some additional
threads on the shank) or add a stack of five or six washers to each bolt
before installation.

AD

 

[Caps4x4]

Fantastic Info. Thank you.
As a side question... I'm 'told' not to use Grade 8 bolts, due to the heat cycling they will incur while on the manifolds.. Something about them stress cracking or something.. Thoughts?

 

[XLT-KID-88]

Your fine to use grade 8 bolts and once you have the right size you can go down to pretty much any hardware store to pick them up i use Tacoma screw