308 Cam Stud Helicoil

Hi - Just refitting my heads and I think, as I had to use a pulling plate to get the heads off fixed back to the cam bearing studs, a couple of the studs have pulled from their threads in the head not allowing me to fully torque the cam nuts.

Ive whipped the studs out, retapped and used stud lock in an attempt to fix but does anyone know if an M6 helicoil kit will fit inside the cam shell locating pins which sit above the head face as shown in the photograph?

http://www.ferrarichat.com/forum/attachment.php?attachmentid=2210051&stc=1&d=1457640665
Image Unavailable, Please Login

 

Inserts come in many configurations, from helicoil to heavy thick O.D. solid type.

I would fit the largest one i could without running hitting the cam. Maybe a margine of .020 -.030".Then make dual O.D. alignment bushing to fit the new hole and the original in the camshaft bearing cap.

On second thought, after looking at photo, I would say a helicoil is your only bet or weld op the hole and redrill and tap.

 

Pull the locating sleeve out and just helicoil the hole. You cant drill the existing hole larger for the helicoil with the sleeve in place.

 

Measure the depth of the shoulder of the hole that acts as the seat for the alignment dowel and set the helicoil that deep.

 

you used a pulling plate that was supposed to go on these studs? What a stupid design!

The torque value for these studs is very low for a reason.

 

Actually a pulling plate locates and fixes to ALL of the cam cover and cam cap studs. 36 studs in total to be exact. With the load divided among this many studs the pulling forces of the head are below the threshold for these threads. I suspect that the OP had studs that were already ready to strip and the pulling plate made no appreciable difference to their outcome.

 

Actually a pulling plate should not be necessary, if the head studs are not rotten solid (aluminium corrosion) in their head holes. Tapping with a rubber hammer all round should be sufficient to pull off the head, in particular such a short one. At least my experience with engines not having the rot issue.

The heads on my Jarama were rotten solid to the block, because the regions of the gasket, which seal water ducts between head and block, had rotten, thus allowing water to enter into the cavity between head studs and holes.

It took weeks of patience and fixing of a head to an engine lift with lifting bands (nylon) and letting it hang with the block (just a few mm above secure ground support, of course), thereby applying creeping oil every few days. That made it over time, without damaging anything, in particular not warping the head (those heads are really long!).

I had thought about making a pulling plate over the full length, but I am sure that this would have nevertheless ruined all head threads of bolts, to which it might have been fixed to.

Cheers, Bernhard

 

i did exactly that too with my 308 ( whic i bought with a broken engne and left outside for 6 years.....). The complete engine hang on the head and the head was hanged on straps. The first head came of after just two days, the second after a week. I applied IMAL daily and gently hammered the studs with a copper hammer, daily

 

Thanks for the constructive replies - I am where I am!

Newman / Brian - Do the sleeves simply pull out?

 

Yes, sometimes they fall out.

 

All sorted, the sleeves just needed to a small turn with an eazy-out. Did 3 in total, all good, M6 helicoils nicely torqued up.

Again, glad I asked on here before I embarked. Thanks again

 

St@ven

Can you explain this a little more? Got pics. Sounds like a simple way to get the heads off but I want to understand it better.

"i did exactly that too with my 308 ( whic i bought with a broken engne and left outside for 6 years.....). The complete engine hang on the head and the head was hanged on straps. The first head came of after just two days, the second after a week. I applied IMAL daily and gently hammered the studs with a copper hammer, daily."

So you are using gravity to separate the head and engine. How did you hang the head on straps? One head at at time or both?

 

I had very good luck removing a stuck head using the nylon "rope trick." You lower the outside cylinders by cranking the engine over, fill the cylinders with 1/2" line through the spark plug hole, then crank the engine over using a breaker bar. This puts the pressure on the cylinder head and the outside of the piston, just like a firing stroke, where the parts are designed to take the stress. Here's the thread with pictures of how I did it:

http://www.ferrarichat.com/forum/308-328-sponsored-yellow-compass-group/458208-observations-gt4-engine-pull-2.html