Impact Wrench on Cam nut

[flmont]

How much of a BAD IDEA is it to use a LOW impact set-up on those cam nuts..???? Frank

[aigel]

I would not use an impact on anyhing but he flywheel bolts. Air ratchet to take bolts off, fine, but an impact on a piece that is 80% aluminum and / or magnesium?

I suppose you have trouble with a breaker bar only? How are you going to hold the cam while applying that impact? I might miss something here? What year engine are you working on?

Cheers, George

[dtw]

I have always used an impact wrench to remove cam nuts on engine teardown; they spin right off. If you are reassembling the motor and removing the cam nuts during your timing setup, then I'd think that is probably a bad idea. Take the time to set up a flywheel lock. The cam nuts come off fine with a flywheel lock and breaker bar.

[ChrisBennet]

I use an impact wrench on cam nuts and bolts all the time. Obviously, it works great for disassembly but it's also nice for removing/installing them when you are timing the cams. When tightening/torquing the big cam nuts by hand, I like to have a helper. (One to hold the crows foot and breaker bar on the nut and one to hold the torque wrench.) The impact wrench lets me do the cam timing by myself and then grab a helper for the final torquing.
Before I owned one, I thought of an impact wrench as a butchers tool. Now I realize, that yes, butchers use them but it's not the tool that's bad.
BTW: Dave mentions removing the cam nuts by using a a flywheel lock to hold the crank. This is probably OK if you are replacing the chain but I wouldn't want to do this otherwise.
-Chris

[flmont]

I am working on a 81 3.0 that has the Nut...Thanks Guys Frank

[911pcars]

The chain links take the brunt of the force when you use an impact wrench. Question is, is there any long term harm to the chain using sudden torque (approx. 200+ ft. lbs) from an impact wrench?

Sherwood Lee
http://members.rennlist.org/911pcars

[Bobboloo]

This is probably OK if you are replacing the chain but I wouldn't want to do this otherwise.

It would seem to me that you also risk damage to the tensioner chain sprockets, intermediate chain sprockets, and intermediate gear. I'm no expert but I think maybe the factory had a reason behind the tools they suggest.

[ChrisBennet]

Originally posted by 911pcars
The chain links take the brunt of the force when you use an impact wrench. Question is, is there any long term harm to the chain using sudden torque (approx. 200+ ft. lbs) from an impact wrench?

Sherwood Lee
http://members.rennlist.org/911pcars

Lee,
I question whether the impact wrench really does put much force on the chain. In the case of the big cam nut, it probably does yank on the chain some if you don't counter hold with the cam wrench. You can see the chain vibrate when you do it. I can't remember if I counter hold the (early) cams or not. Now that you've made me think about it I will be sure to.

In the case of the later style cams ('83-?) I think impacting the cam bolt tugs on the chain very little if at all.

An impact wrench uses lots of little "rabbit punches" that are so fast that the inertia of the cam isn't overcome i.e. you don't even need to hold the later style (bolt) cam.
This became evident to me once when I was timing cams a few years ago, With the cam set up for timing and the dial indicator reading around 1.25mm, impacting the cam bolt changed the reading by .02mm. For those of you who haven't timed cams before, you only need to breath on the cam to change the value by that much or more.
-Chris

[Wayne 962]

Impact wrench should be okay for removal *only*...

-Wayne

[flmont]

Yes,..The impact wrench worked great,..did'nt even stress the chains at all...Frank

[Wayne 962]

Originally posted by ChrisBennet
...impacting the cam bolt changed the reading by .02mm...

I don't recommend using an impact wrench to tighten anything of importance. The torque controls inside the wrenches are not precise, and you can easily overtorque or undertorque a fastener...

-Wayne

[ChrisBennet]

Originally posted by Wayne at Pelican Parts
I don't recommend using an impact wrench to tighten anything of importance. The torque controls inside the wrenches are not precise, and you can easily overtorque or undertorque a fastener...

-Wayne

Timing cams is a "tighten bolt, measure it, move pin and repeat" sort of process. I don't find it necessary to tighten tighten the cam bolt to it's full torque spec during this part of the process. With some experience, a little "burp" with an impact wrench tightens the bolt well below it's torque spec. When I get the reading I'm looking for, then I torque the bolt and do a final check.
-Chris

[Wayne 962]

Chris,

While you may have the expertise to only torque to a certain amount, I can imagine many others who think that a 'blurp' is longer than you would think. While probably okay for expert mechanics (like yourself), I really wouldn't recommend this for the average joe...

-Wayne