Trouble with 1438 cam box studs

[Davin]

Hi folks, still relatively new to the Fiat TC world so patience appreciated.

I chased an increasingly-severe oil leak on the exhaust side of my 1438 Coupe to the gasket under the cam box/tower at the corner closest to the firewall. I figured a simple first move would be to re-torque the nuts holding the cam box to the head. I've read between 14 and 21 foot pounds are needed here, so decided to start at 14.

Unfortunately the nut on the stud directly over the oil leak just kept spinning. And sure enough when I double nutted the stud to try to snug it down it would not tighten into the head. This is the rear-most external cam box stud on the exhaust side. Perhaps foolishly I then did the same check on the next stud forward and found to my horror that it too wanted to spin rather than snug down into the head.

Knowing aluminum heads, I was really trying to be delicate, but anyway here we are. The leak has now become a gusher, rendering the car undriveable.

I'll double nut and pull out these studs to inspect them next. My question is where to go from there. Searching does not bring up much info on these studs, so maybe this is an unusual situation . . ?

Are the holes those studs thread into blind? Can I safely run a thread tap in to try to clean things? And possibly drill down a bit farther to chase new threads for a longer stud?

Have never had the head off one of these cars so I don't know quite what I'm dealing with in terms of these studs. This car is my quasi daily driver, so I'd love not to have to pull the tower entirely and do a timesert/helicoil if I can at all avoid it.

Thanks for any advice you all may have!

-Davin in London

[RRoller123]

On the 2L engine the Cam Boxes are held down by bolts, not nuts on studs (I assume same on the others?), but at any rate, the Cam Boxes are not too hard to remove, have the thread repaired, and reinstalled. It will just all take a little time. Just need to remember to do a new belt at the same time, use new gaskets, and recheck the valve clearances afterwards. I put a very thin layer of high temp sealant on the gasket for the Cam Boxes. This is pretty much the only area where it seems to really be needed, a very common source of leakage as seen by the frequency it is reported here. None on the head Gasket, none on the Valve Cover gaskets, none on the Exhaust and Intake Manifold gaskets, but I do use it here on the Cam Box gaskets. Very thin.

Just to note while you are at it: Some of the exhaust and intake manifold studs pass through into the oil pool inside the cam boxes. For the Intake Manifold, it is #2 and #5, for the Exhaust side, it is # 2 and #4.

Exhaust side:



Intake example:

[Davin]

Thank you very much for the reply, RRoller.

I can confirm indeed that these are nuts on studs on the original motor in my 1968 1438 AC. I was really hoping the leak would be one of the upper exhaust mani studs, just as you pictured. No such luck this time. Good to know that sealant is good practice on the cam tower-to-head gasket.

For those who know early cylinder heads: what is below the bore of these cam tower studs? Would be really nice if it's no problem to drill these a bit deeper and cut some new threads.

If I have to I'll remove the tower and do all of the 'while you're in there' items as you mention RRoller. This engine is quite fresh from a P.O. rebuild however, and it's prime driving weather here in the UK. I'm a slow wrench, so I'd love not to have to dig in that far haha.

[Davin]

Before I tear into it, does anyone out there have advice on thread correction for cam tower studs on a 1438 cylinder head? Most importantly, are the bores blind?

It would be nice if I can safely either drill the bores deeper into the head to run a longer stud on clean threads, or failing that, whether I can enlarge the bores to take a helicoil/timesert thread repair.

Thanks once again.