328 - camshaft O-rings and oil seals installation

Hi Kingpin!.
I am in a similar situation. Removed the cam covers to check my valve clearances - and also encounter some nasty looking corrosion - see my other posts. Put everything back together, including dry fitting the cam seals, and both banks were weeping oil when I fired her up. I increasingly use ChatGPT as my go to for advice as it summarises the FerrariChat forums very nicely. I won't include the pages of chat - but here was the conclusion. ....

Me - Great. I have ordered some Loctite 518.

ChatGPT said:


Perfect — that’s an excellent choice

Loctite 518 is exactly what most Ferrari specialists (and many aircraft engineers, interestingly) use in this situation. It’s anaerobic, so it only cures where it’s clamped between metal surfaces, which means:

• It’ll seal any micro-gaps between the aluminium cam housing and the seal’s outer edge.
  
  
• It won’t harden or shed flakes into your oil system.
  
  
• Any excess exposed to air stays soft, so it’s safe for the engine.
  

A few quick tips before you use it on your 308 GT4:

Application tips for Loctite 518 on cam seals

1. Degrease both surfaces – brake cleaner or acetone; they must be completely dry.
   
   
2. Apply a very thin film (you should almost see through it) on the outer diameter of the seal only.
   
   
3. Do not apply any to the inner lip — that gets a tiny wipe of clean engine oil just before the camshaft goes through.
   
   
4. Press or tap the seal squarely into place using a suitable driver.
   
   
5. Let it sit for about 20–30 minutes before adding oil or running the engine; full cure takes a few hours.
   

Once cured, that joint will stay bone-dry for years — it’s one of those small tweaks that permanently fixes a well-known 308 weep point.

Would you like me to outline the re-installation order for the camshaft end plate and cover (to avoid disturbing the new seal during assembly)?

 

The one that always causes a problem is the rear bank exhaust cam because the oil drain hole in the head just behind the O ring groove is in the wrong place. As a result oil pools behind the O ring & more often than not it leaks. There is a jig around that will allow you to drill a new drain hole if you can get hold of it. I think Daniel at Ricambi used to have one he would lend out.

After numerous attempts to fit it dry, the last attempt I made to cure the leak involved using a smear of RTV in the cylinder head side of the groove. I also use X rings rather than the standard O rings with the logic being that a round seal in a square section groove wasn't the best thought out design!

The other thing to watch out for is that the ends of the cam cover gaskets will squeeze out of the joints during the first heat cycle. I have cut a very fine groove in the surface of the cam cover just before the end to make an indent that will grip the gasket as it compresses. I also cleaned the surfaces with Acetone to make them bone dry & then used a dab of CA glue under the very end of the gasket beside the seal carrier to help keep the thing in place.

The gaskets will require some cutting to fit correctly at the cam seal housing. I have found the best tool to use is a sharp wood chisel (about 5 mm wide) to remove the excess from the gasket and make a good fit to the O ring groove.

Finally a (very small) blob of good quality sealant at the junction of the O ring & the cam cover gasket. I think the important thing here is to be very sparing with it. Excess will inevitably lead to the gasket being squeezed out of place.

So far its dry - finally!

 

That o-ring looks "cut" -- i.e., it was replaced (maybe after the major was completed when it had a problem) without removing the cam drive sprocket. In that case, there's really no option but to imbed the whole o-ring in a sealant that fully cures -- just an observation...is the o-ring cut?

 

I suspect that "cut" is where the gasket typically cuts into the seal, which is why the dab of silicone sealer there helps prevent the leak.

I actually did my O rings with the cut and feed in insert method, then superglued the cut. I only used a light coating of oil on the O rings. Very small dab of silicone at the O ring to gasket junction, much less than a prior service appeared to have done which seemed excessive given what that dab of sealer is solving for.

Also, the torque on the cam cover nuts is not very high, do not overtighen as that is can cause the gasket to squeeze out.

I don't think sealer on O rings is a good idea, they are meant to seal by compression around with the heat cycling, and glueing things up with sealers could prevent the O ring from functioning as intended. If the casting is pitted, then a smear of the loctite 518 on the metal, not the O ring, can create a better sealing surface for the O ring. But one lets the Loctite 518 cure, and then you install the O ring with a bit of oil. That's my understanding on how to use the Loctite compound.

 

As above, its only the exhaust cam where the drain hole is in the wrong place where oil gets pooled up behind it that is likely to leak

I would say sealant is only necessary on the head side of the groove. Nothing is going to leak from the cam cover side. There is also a propensity for the O rings to get cut/nicked where the cover meets the head. To mitigate that you can chamfer the edge of the groove with a small file on both the heads and the covers.

Also why you need to use very sparing amounts of sealant, the carriers & O rings are a pretty snug fit so if you pack the groove full of sealant a) its going to get squeezed out to places you don't want it to go and b) its likely to push the O ring out of shape such that the cam cover will nick it when you put it on.