Why studs?

[ashaughnessy]

Why use studs on an engine instead of nuts and bolts? On my crossflow there are four bolts and one stud to hold the inlet manifold to the head, why not just use five bolts? Then there are eight studs to mount the carbs on, why not use nuts and bolts? What's the advantage of studs? I'm asking because the studs have been giving me a little trouble during assembly and I'm sure it would be easier if they were just nuts and bolts.

Anthony

[felix.klauser]

There are several plausible reasons...

 

In in ali head or block (doesn't apply to the crossflow!) studs are better so that repeated installation and removal doesn't damage threads in the ali.

 

If the bolt is long there might not be clearance to pull it out all the way when removing it.

 

Studs sometimes simplify the assembly of something by helping to locate two mating pieces.

 

I'm sure there are other reasons as well...

 

[Roger King]

The stud in the cylinder head for mounting the inlet manifold is there partly because the hole goes through to the water jacket. If a bolt were used it would probably leak water unless sealed. A stud can be fitted and sealed to permanently stop this happening. You can use a bolt if you wish, but you will have to use Loctite hydraulic sealant or similar to stop the drips. It is also easier to put the manifold onto the stud and then attach the other four screws than it is to hold the manifold in one hand and try to get a screw in with the other.

 

The carbs have to be flexibly mounted. If bolts were used, you would have to leave them loose in order to allow the carbs to flex on their mounts and they would probably fall out. By using studs with nylocs, you don't have to worry about things coming undone (if assembled correctly).

[ashaughnessy]

...and of course when I fitted the stud in the inlet manifold that goes through to the water, I took great care to make sure it was sealed against water egress...didn't I? B*****ks. I tightened it up reasonably tight with a pair of locking nuts on it before putting the manifold back, but didn't do more than that. I've got some loctite hydraulic sealant, perhaps I should remove the stud and apply some of it to make sure.

[sjwb]

Location, location, location!

 

Steve B

[oilyhands]

In addition there is always the chance / danger of a bolt 'bottoming out' and damaging the thread in the head,or breaking through into a waterway / other bolt hole. Continual disassembly of a joint using bolts and a threaded hole can also damage/wear the thread. A damaged thread in a head casting is more difficult to cure than a damaged thread on a stud where you can simply replace the stud.

 

Oily