Timing Cover Crack Avoidance

[michbc3]

It's very easy to crack these Buick timing cover castings when torque'ing down the upper bolt that supports the crankshaft sensor bracket. I've cracked two covers so far; and of course this is a costly and time consuming mistake.

The shop manual calls for 22 lb-ft on this fastener which I believe is way too much. I'm going to use a nutdriver with "wrist torque" on this particular bolt from now on. The factory torque spec might be ok to use on the longer bolts where the casting is stronger, so I'll probably continue to use more torque on those.

I'd like to caution others about this.

Best, Bob

 

[WS6]

I have never heard of this? 22ft lbs,really? on a bolt that small? I would have thought 10-14 max.

2 covers....that is expensive!!

 

[michbc3]

This is a 3/8" bolt. Page 6A5-35 of the Service Manual Supplement says: Front Cover bolt = 30 NM (22 lb. ft.). Don't buy that spec!!!

I torqued that second one up as slowly as I could and just as it hit 22, I heard it crack. I just about went out of my mind - and am still reeling from this. I waited about a month to get that cover (and it has internal oiling mods, a new HV pump and adjustable bypass spring) = extra expensive...

I'm going to smear some silicon in the crack, run it and keep my eye on it. If that doesn't do the trick, I may be able to get it welded - but that could add a month or so - finding the right guy to do that.

 

[WS6]

A local GN owner and friend of mine had a really nice cover that had excessive wear on the cam button area.So he took it to a welder who specializes in alloys like aluminum(micro welding) and he welded that surface up and then I took the cover to a machine shop with my good cover as a reference piece and he machined the welded surface for the cam button.

Anyway...the welder said that cover was the worst grade of aluminum he had ever tig welded.He almost gave up on it,so if you still plan on welding it. Don't be disappointed if it can't be done.

I hate to even say it but maybe an epoxy is the safest way to go.


..

 

[michbc3]

Welding this crack would be much more complicated than fixing the cam button area. So epoxy or silicon sealer is going to have to do.

If it can't be fixed or made to work my next purchase will be a sledge hammer to turn this thing back into sand.

 

[Jan Larsson]

Is the cover sitting flat against the engine block or do you bend it when tourqing down that bolt? Can't remember having an issues with mine and I know mine was straight as I checked it with a straight edge.

 

[michbc3]

I'm going to check flatness but don't expect a problem.

Regardless, 22 ft lbs is simply too much and not necssary for the short bolts at the edges and corners. I'm going to use about half of that torque from now on. Taking no chances.

For the long bolts that feed through the steel water pump, 22 is probably ok and necessary as the water pump pulley on front has to be supported of course. Too bad that the shop manual didn't make that distinction.