1959' Warped Timing Chain Cover Bolt Holes on a 390ci

[Coupe Deville]

Hello everyone,

Not sure if my torque wrench is inaccurate, or if my factory reproduction shop manual is wrong (says 10-12ft-lbs), but while I was putting my dads 390 back together today I was torquing the timing chain cover bolts (I got to the third bolt up and realized something was wrong when the cork gasket squeezed out and split) and those three bolt holes got warped. So what is the proper procedure for making them flat again? I'm a little upset because I was finally going to get the front of the engine all back together today, and I just painted the cover today, so if Ive got to start banging this thing I will probably have to repaint it.. Oh well. The new gasket will be here tomorrow, and I still have more than half the can of Bill Hirsch Cadillac Blue left. I think I'm going to borrow my friends torque wrench for this tomorrow. The bolts felt really tight when torquing them down, and I made sure the torque wrench was at 12ft-lbs. I never had a problem like this before.

Thank you.

-Gavin

[The Tassie Devil(le)]

The book does say 10 to 12 ft. lbs.

I have never heard of "warped" heads.   Sounds to me like they are about to break.

Me thinks that your torque wrench was incorrectly adjusted.

Bruce.

[n2caddies]

Hi Gavin
Any chance you have the wrong bolts and they are too long?
Randy

[Coupe Deville]

Maybe I wasn't very clear, my apologies.

The bolt holes, (the through holes) on the timing chain cover are now warped, bent, inverted inward. Like when you over-tighten a oil pan and it leaves those bumps on the pan. I'll try and snap a picture tomorrow morning. I'm pretty sure I have the correct bolts. The 9 bolts for the front cover. They don't bottom out in the block. Probably cant make good sense of it right now because I'm really tired. Back in the morning. 

Thanks for the responses.

[Bobby B]

Gavin,
Hi. As stated above, I would check my torque wrench against another one. I've had them hang up sometimes in the rachet mechanism. Before you put that wrench away, do you turn it all the way down to take the tension off of it? Did you ever use it to loosen a nut/bolt? 12 ft.lbs. is easily obtained with 1/4" drive tools. Lucky you didn't break something…..
                       Bobby

[Roger Zimmermann]

I never torque those small bolts with a torque wrench. Just by feeling and I don't have a leaking gasket...

[The Tassie Devil(le)]

Ah ha.   Bending the flange.

This is corrected by simply holding the timing cover against a flat piece of steel, or any flat surface will do, as a mandrel, with the bolt-side to the mandrel.   Then simply with a small hammer, restore the flange to its' original shape, that is flat.

Don't hit too hard as to distort the outer right-angle edge of the flange, but just enough to flatten the bolting surface.

Bruce.

[76eldo]

I agree on not using a torque wrench on small items like that cover.

Snug plus a little bit would be my setting.

High clamp items like head bolts need to be torqued to a setting but if you straighten out the cover bolt holes and just snug everything down it won't leak.
Your torque wrench must be way off or maybe it was dropped a few times.

Good luck.

Brian

[savemy67]

Hello Gavin,

Like others have posted, your torque wrench could be out of calibration, and the shop manual could be incorrect.  My original '67 shop manual is incorrect in a few places when it comes to bolt diameter, pitch, and torque specification - bummer.

For small bolts with a presumably low torque specification, you may want to get a beam-type torque wrench.  This type of torque wrench may not be as accurate as an expensive click-type torque wrench, but it may give you a better feel when torquing small fasteners.

You may also want to check some of the fastener/engineering web sites that provide charts showing the maximum torque values for fasteners of a given diameter and pitch.  This is where I found that my shop manual was incorrect.

On many stamped steel covers, the circumference of the bolt hole is slightly raised on the bolt head side of the cover.  This feature helps to ensure that the cover squeezes the gasket just the right amount.  Overtightening, as you found out, distorts the area around the bolt hole in the opposite direction.  If your cover's bolt holes were originally flat, you can restore the area around the bolt holes per Bruce's instructions.  If your cover's bolt holes originally had a raised circumference on the bolt head side of the cover, you can restore the raised circumference by placing the cover on a bench, engine side up.  Place a socket under the bolt hole (be sure the socket is flat against the cover under the bolt hole and not against the flange).  Place a large ball-bearing on the engine side of the hole and hit the bearing with a hammer.  In effect, you are trying to dimple the area around the hole (when seen from the engine side of the cover).  If you can't find a ball bearing of the appropriate size, you could use the ball end of a small ball-peen hammer, the face of which you would hit with another hammer.  Remember,  striking two hammers face to face is not recommended so wear safety glasses and proceed at your own risk.  And did I say you should wear safety glasses?  Good Luck.

Christopher Winter