timing chain guide derailed

[rogwilson]

Decided to upgrade my tensioners on 1980 911 during the holidays. They sounded loose with a metallic clanging noise at idle.

Pulled off the right cam chain housing cover to discover the black rail from the top had broken off and was at the bottom of the case. The pin that snaps into the guide was still in the guide at the bottom of the case along with the parts of another rail. Question and/or serious problem. The pin appears to either have snapped or was pulled out. I can see what appears to be a line of threads on the end.

Is this pin threaded and screwed in from the inside or outside of the case or is it pressed in? If it has snapped and the threaded portion is still inside of the case, how would you go about getting it out or fixing the problem. Thanks.

[rogwilson]

update: the pieces of rail belong to the missing top inboard rail. So it looks like I will need to order all new rails.

Does anyone know if the pins for the outboard rails are pressed in or threaded in from inside the housing case?

I will attempt to enclose a picture. If the fix involves removing the cam housing and retiming I will probably have to flatbed it somewhere in Indianapolis for repair.

[rcwaldo]

I had a similar issue with a 74 911. The pins (at least in the 74) were pressed in and bonded at the ends, outside the chain box casting.

Once the pins come loose, they tend to oval out the bores in which they are pressed into. You may need to find a good used housing and swap it.

Let us know what happens...


Chris

[rogwilson]

thanks for the response Chris.

I have since checked the porsche parts CD which shows the pin pressed into the housing in the '74 and '80. you were right. pelican does sell a new chain case for a couple hundred dollars.

the bore does not appear to be oval shaped. i suppose the chain slapping around in there eventally pulled it out.

i am considering pressing it back in with Loctite's "Cold Weld Bonding Compound" or maybe some other bonding compound.

If anyone has an alternative let me know. thanks

[HawgRyder]

Perhaps an oversized stepped pin with threads on one end.
Overbore the hole and tap it....then install the new stud.
Or...overbore for a heli-coil...and screw in a non-stepped but correct size stud.
Bob

[atr911]

Or you could buy a chain housing from me in mint condition. $50 if you're game. I have a 3.0 engine from an 78 911 that I've parted out and just happen to have a pair kicking around.

Drop me a line and let me know,

Adam
a_roseneck@hotmail.com

[yelcab1]

That $50 offer is the best solution. Easier, and cleaner than messing with new pin, tap, drill, and loctite. THen, you may end up buying a housing anyway.

[rogwilson]

thanks for the input. i agree the best solution would be to put in a different housing. But i do not have all the tools necessary to retime the cams at this point.

So, today I repressed the pin in (it took considerable force) with permatex High Strength Sleeve Retainer and bonded the end with permatex Cold Weld. both products have a shear strength of greater than 3000 psi.

After it sets up and if there is any doubt about the strenght of the bond or the security of the pin i will take Adam up on his offer.

by the way, if you ever hear a metallic knocking sound from your chain cover area, don't hesitate to check it out. the previous mechanic told me not to worry about a chain tensioner upgrade. He had put safety collars on the mechanical ones. i believe my tensioners weakened, the chain flopped around, and eventually beat the chain rails up. just lucky that the pin did not feed through the gears. If that had happened we all know the rest of the story .......

[atr911]

I had the stoppers on my tensioners and one of them was cracked when I took it apart. It hadn't caused any dammage at that point but i'm sure it would have eventually.

Adam