Manifold bolts

[ggenovez]

Hi all,

I just finished removing the manifold from my 72 250 to replace the manifold gasket. I wish someone had informed me to drain the coolant. What a mess when I pulled one of the manifold bolts.

Ok. I noticed that some of the bolts had something that looked like a castle nut. Some did not and some had a bunch of washers stacked together. I'm guessing that I need to replace the stack o washers with tha castle nuts. Anybody knows how many I need?

Also, one of the bolts, the second from the left, as a stud with a torc-40 bit.

Is that the right piece? If not, where can I get replacement bolts? I'm guessing any local autoparts shop, but would they have the metric bolts?

Thanks

G

[Mike D]

Any Ace hardware will have the HARDENED bolts. Make sure you use "Never-seize" when you re-install them. I'd guess someone has removed the A/C or some related brackets and replaced the same bolts using the castle-nuts as spacers.

While you have the manifold off either use a good straight-edge or take it to a machine shop and have the trueness checked. Use a tap and clean the threads. Be gentle, do not force the tap past the bottom of the threads as you can crack the head.

[cth350]

The correct fasteners for the manifolds on a straight 6 are studs. Make sure that all are the same diameter and thread. Except for the two long thin ones that hold the thermostat housing in place.

The correct nuts on the studs are a deformed copper alloy nut. BMW, VW and mercedes all use the same nuts. There should be a single washer between the nut and manifold.

My guess, based on how you described the hardware, is that one or more fasteners has been replaced and the threads could be the wrong size (SAE vs Metric or fine vs coarse). Like Mike said, don't force anything.

-CTH

[cth350]

PS. The correct studs from the dealer should be about 2$ each. Ditto the nuts. -CTH

[300SDog]

Yeah there aint no "manifold bolts".... all of em oughta be dowel studs'n nuts, self-locking castle nuts. And the washers should be one thick smooth faced washer with beveled edges on earlier versions.

Gotta order a fresh set of dowels, washers and nuts - thats what you've got to do. Now here's the news - good and bad - which do you want first?

On the darkside your 250/8 has been previously scotched by sloppy mechanics. On the brightside it has seen mandatory once-in-lifetime cyl head work done at/near 130k miles. Possibly prior repair of blown head gasket? Otherwise why should anybody pull the manifolds? It strikes me your manifold gasket leak is directly related to cheap labor attaching em. But lets hope they didnt strip fragile alloy cyl head threads in the process.

[ggenovez]

Thanks guys,

Anybody have the part numbers? I was at the dealer today and they had a hard time finding the 45' tube that connects the manifold to the air filter houseing. They never did find that piece.

Thanks again.

G

[ggenovez]

BTW, is that 1 stud with what looks like a torq bit at the ond of it the correct one?

I had a bear of a time getting the manifold off with that 1 stud.

[ctaylor738]

No, it's bogus. Somebody cobbed it with what they had laying around in the shop. You really need to use the correct studs, flat washers, and nuts. The studs need to be the right length. Too short, and you can't get enough of the nut on, too long and you can't get the manifold to clear.

But I will say that the world will not end if you use a couple of studs to position it, and use bolts for the rest. Just make sure the bolts are the right length. Either way, dont forget the flat washers.

I believe that the exhaust studs are different from the intake.

You can make the hose from the air cleaner to the intake from fuel line or PS hose or even heater hose. It's kind of tricky getting the length right because it needs to be a bit (maybe an inch) too long so that you can connect it as you install the air cleaner.

[t walgamuth]

i agree totally with the above post.

i would emphasize that using the factory studs is best. they thread into your aluminum head. the correct length of threads is crucial because you need about three diameters of the steel fastener worth of thread in the aluminum head to develop its strength.

(this means if you have a 10mm diameter steel fastener screwing into aluminum, the length of threads necessary to develop the strength of the fastener in the aluminum head will be in round numbers 30mm. if you were screwing steel into steel the 10mm fastener would require 10mm of threads, assuming the strengths of the two steels are the same).

if you use threads that are not long enough when you apply enough torque to hold the fastener you will strip out the aluminum threads. (this will generate a lot of extra work).

so take your time and find the correct factory studs and then meticulously follow the torquing directions. you will not regret doing it right the first time. doing it over really sucks!

dont ask how i know all this.

good luck

tom w

[Mike D]

Don't use heater hose. Use vacuum line, fuel line or better yet PCV hose. Hydrocarbons will attack heater hose and cause it to soften and swell.