Why studs on a Thermostat housing?

[vping]

Why are studs used on a Thermostat housing and not bolts? These studs I ordered through a local friend and they are the wrong length. I want to just run down to the local hardware store and pick up some stainless.

Oh and I posted about modifying the housing and here it is.

 

[Steve_S]

You can replace them with bolts. Use anti-seize.

 

[vping]

Are these a standard coarse thread? I cannot find a bolt to fit.

 

[DrEntropy]

Fine thread, Vince. 5/16" NF, IIRC.

 

[piman]

Hello Vping,

it's better to have studs into a casting rather than bolts as there is less likelyhood of damaging the tapped threads in the head (or any other casting), particularly in a location that is often dismantled.

I'm virtually certain the studs are 5\16" UNC, block end and 5\16" UNF, nut end.
Also I would not use stainless as it is often brittle and prone to thread pick up (usually when hot). Just use copper grease when assembling.

Alec

 

[Steve_S]

I wouldn't go so far as to say the thermostat housing is often dismantled. I take one off every five years or so. But it's true that studs will cause less wear from removal and reinstallation.

 

[tony barnhill]

Why? Saves bottoming out a bolt that's too long & cracking a head. 'Cause DPO's will do that, trust me!

 

[DrEntropy]

I'm virtually certain the studs are 5\16" UNC, block end and 5\16" UNF, nut end.

I must agree: Head end coarse thread, "air" end fine. I just pulled one to check. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[vping]

Must be a stud that is 5/16-18 on one end & 5/16-24 on the other.

 

[piman]

Hello Steve,

some people like to swap thermostats, winter and summer, however on a thirty or forty year old car once every five years is 'quite often'

Alec

 

[dklawson]

On the A-series engines it's very common for the t-stat housing to seize to the studs. This frequently means that changing the t-stat results in broken housings and/or snapped off studs. Is a broken stud in a head any better than galled threads from using a different material bolt?

I use stainless bolts instead of the studs. I also use anti-seize on the threads )AND way up the bolt shank) as Piman suggested. I don't want to break any more t-stat housings and using the anti-seize compound both protects the thread from galling and prevents the bolts from corroding to the housing.

As for running too deep or over torquing as Tony mentioned, you'll be selecting the bolts and you'll be tightening them. Buy the "correct" length so they don't bottom out and/or saw them off to length and file away the burrs on the cut end. That way you know they won't go too deep. As for over-tightening... if you're not over-tightening the nut on the stud why would you be more likely to over-tighten the bolts?