Hi, fellas.

What torque spec would it be for intake manifold studs into the block on my 351w?

I know the nuts would be about 18ft-lb.

Thank you - Thomas

 

To tell the truth I have never looked other than the order they need to be tighten.

Why do you say 18 ftlb on the nuts?
If the nut /stud is the same size as the bolts, 5/16?, why not the same 18 ftlb?
Dave ----

 

Doesn't the intake bolt to the heads?

Given the V configuration, how will you get the manifold on with the studs sticking up at an angle?

 

Don't overdo it on the nuts. I do not think the studs would matter. But if you over torque the bolts/nuts on a Ford intake, it can affect the head bolt torque.

 

The bolts point straight up and down. The holes in the heads are angled to match.

 

thanks. Too long since I worked on a SBF

 

I was taught studs in a blind hole should be threaded just a little more than finger tight. Maybe 20 in-lbs, which is about what you'd get with a screwdriver.

This takes up the free play in the threads, without putting excess force on them. Use threadlocking compound.

Do the top end of the studs have fine or coarse threads? Whatever torque value Ford specified was based on coarse thread bolts. If you torque coarse threads to a certain torque, you will obtain X amount of clamping force, which is what really matters. If you torque a fine thread nut the same, the change in thread pitch changes the clamping force. Having a brain fart, but I believe this increases the clamping force so you'd have to reduce the torque to compensate.

Not sure where to look, but there must be something online with a formula to use. Any instructions with the stud kit?

 

Thanks, fellas.
I had a brain fart. I was thinking for some reason the studs went into the block. But they go into my aluminum heads.
I haven't received the stud kit in the mail yet but it looks like there are no instructions and the threads look different on each stud - course vs. fine.

Thank you - Thomas

 

The formula relating torque to clamping force is
T=kDP

where T is torque, in-lbs
k is the friction factor
D is the diameter of the bolt, inches
P is the clamping force, lbs

The clamping force is independent of the thread coarseness. Not in the formula.

 

I just read that k, the friction factor is affected by the type of thread. They said k has many different factors to it, like thread pitch, oily threads, rusty threads, etc.

 

Oy vey! Did I ever open a can of worms. I got to poking around, looking for something definitive from an engineering or authoritative source. I wanted to stay away from the opinions of people who have no clue what they're talking about, such as yours truly.

Turns out the equation previously mentioned is the short form. Factor "k" involves all sorts of things, especially thread pitch and friction. This article mentions the long form equation, and explains how "k" is basically a fudge factor, making a bunch of assumptions for the sake of simplicity. But then again, this article is written by a woman so take it with a grain of salt

https://www.machinedesign.com/fasten...n-relationship

Here's another article on the subject:

https://www.assemblymag.com/articles...ue-and-tension


In a nutshell, thread pitch has only a minor effect on the clamping force generated by a threaded fastener. In extremely critical applications, an engineer would use the long form equation. But in practice, the short form equation is used nearly all the time and not much consideration is given to thread pitch.

Think of thread pitch like an inclined ramp, conveniently wrapped around a cylinder. If you decrease the thread pitch, the angle of the ramp decreases so you gain a mechanical advantage when applying the same horizontal force to "push" something up the ramp. This increases the clamping force, but the change is very slight as many other factors are also in play.

In my over-inflated opinion, I'd shoot for the lower end of the originally specified torque range and call it good.

None of this is to be construed as me being W word, but merely less correct than usual.

 

Relax, bro...don't get your pronouns in a bunch. You were only W by a few percent. But what's a W anyway?

There's no clamping force till the nut or the head is engaged. Then since coarse threads are deeper than fine the surface area over which friction acts on thread faces balance somewhat. Then you have the testing on T vs P varying 2 to 4 times more than the theoretical pitch factor and then engineers like to have a safety factor on top of that variation, you're probably good to go with the specified torque.

 

Alright. Holy Mother of Pearl!!! I'm going to go 18lb/ft on the stud going into the aluminum heads and then 18lb/ft on the nut holding down the intake.
Thank you - Thomas

 

Don't make me break out my ruler!:



Minimal torque only when installing the studs. Regular torque on the nuts, but minimal torque when first installing the studs by themselves.

Here's what ARP has to say about installing cylinder head studs. Unless I'm mistaken (can't see how that's even remotely possible...), this should also apply to any brand or application, whether it's a cylinder head or intake manifold:

https://arp-bolts.com/p/faq.php

"cylinder head studs are installed only hand tight. Other than the use of an allen wrench on the hex broached into the end of the stud (to ease installation, not to apply torque), use no tools to seat them in the block. However, it is extremely important to ensure that the studs are fully bottomed out in the hole in the block and not hung up on damaged or corroded threads in the block preventing the stud from being fully seated. This is often indicated when the stud threads extend past the deck surface."

 

Great information. Thank you!
- Thomas