In my soon to come 3.4 engine assembly I would like to gain an option of removing the front cover with cylinder head in place. It seems that only bolts holding the front cover perpendicular to crank axis are the two going down through cylinder head to the cover and sump bolts. My plan is to replace these studs with equivalent Allen bolts, so they can be easily removed, allowing the cover to be taken off horizontally to the front.
Is my plan doable / reasonable ? I’d love to able to inspect lower timing chain, etc. I have read that it’s no easy task, but at least without upper studs it should be easier at first.
Removing those studs is the only way to remove the front cover without removing the Cyl hd.
I can see no problem with replacing them with cap screws, one thing to check is that imp cap screws from memory have smaller o/a head diametre so I would check what bearing area you have.
It’s not likely to make it easier to R&R the part without removing the head. The one time I tried it, I had no issues extracting the 5/16" studs using double nuts. The issue was the clamping force, and risk of snaring the head gasket as you try to reinsert it, and fact that you can’t add any kind of sealant to try to restore the seal around the timing cavity because it will all just squeeze out, or worse into the cavity where it threatens your oil supply. You’re free to substitute whatever type of fasteners makes you happy so long as the thread pitch is right, but the awkward geometry of the assembly remains the same.
Yes, and having managed to take the timing cover off and refit with sump and head in place - I was very pleased the car had an old style metal head gasket. I think “snaring” the head would be harder to avoid with a composite gasket.
My suggestion would be to use 12 point cap screws instead of hex socket screws. The 12 point head is bulletproof. No risk of destroying the internal hex. Much easier to torque. (random length shown below)
Here’s a little comparison of three 5/16" UNF cap screws. From left to right, a 12 point alloy, a hex socket and a hex socket pretending to be a stud with a standard hex nut. The ratchet and breaker bar are both 1/4" drive.
The 12 point screw requires a 5/16" 12 point driver. You can get that in either a box end wrench or 12 point socket. In tight quarters, it’s hard to beat a 12 point and a box end.
The hex socket requires a 1/4" hex key. Beyond the risk of cam-out and stripping the hex, the number one socket hex limitation is that it requires a minimum of a 60 degree arc swing, 12 points cuts that in half.
The standard nut on stud requires a 1/2" socket or wrench.
One risk of using a screw in place of a stud is that you are threading a hardened steel fastener into a soft aluminum casting. If that was something I expected to cycle frequently, I’d put a Helicoil in the head to prevent stripping the threads.