560 SL cyl head gasket, heli coil necessary

[Roncallo]

Gentlemen

As I get ready to replace my 560 SL head gasket, I am reading some articles that say helicoiling the threads is almost mandetory. Can anyone share there experiances with this.

I'm surprised that the block does not come with some kind of thread inserts from the factory.

Are there any trickes to this.

Are there any thin wall areas that I have to be concerned with.

Thank You
John Roncallo

[duxthe1]

Of all the aluminum v-8s, the only ones I've experienced thread problems in the block were the 380's. Out of several I've never had any threads pull on a 560 block. The 380's that have given problems all had been apart previously. So if it's the first time your engine has been apart and it will be the first head torquing since the factory did it you've got virtually nothing to worry about. Just make sure the bolts and bolt holes are clean and lighly lubricated and you'll be fine.

[CzarFC]

You shouldn't need to helicoil the head bolts unless they're damaged. I'm in the middle of rebuilding a 560 myself (although mine is the SEL) and I did wind up helicoiling some threads, (one head bolt and 2 of the little guys around the timing chain). Only helicoil them if the threads are damaged or stripped. Before putting the head back on, take a bolt and test it in each threaded hole, if it goes in cleanly, call it good.


Best of luck!

Scott

[Roncallo]

This all sounds promising but is there any rerason to avoid heli coiling like thin wall areas or difficuly getting at some of the threads with the engine? Or is it difficult to mask off oil and cooling passages or perhaps some bolt holes penetrate into oil or cooling passages? If I had this block all striped down it seems to me that helicoiling every thread would be my standard proceedure.

Thank You
John Roncallo

[CzarFC]

The walls are all beefy enough to helicoil them all, however, the PITA will be helicoiling the right/driver's side bottom holes. All the 10mm holes are blind (ie don't protrude through oil/coolant passages as do the fore and aft bolts on the uppen intake manifold). Most of the 8mm holes (forward of the timing chain) are thru holes and the chips can easily become FOD. I HAD to helicoil a couple of those holes and to do them I soaked a couple of paper towels in oil and stuffed them behind where I was drilling and tapping. It seemed to work. I'd look at it as a cost/benefit analysis. If the Al threads are good enough why drill them out oversize re-tap and helicoil insert if you don't have to. Besides, its a lot of taping up and alot of FOD potential. By helicoiling the threads, do you make them stronger? Absolutly. However, My opinion is if it ain't broke don't fix it.

Again, my advice is to test each of the threads and if the bolt goes in a reasonable length of travel then don't mess with it.

Either way, best of luck!


Scott

[psfred]

Later engines have steel inserts from the factory. 380 and 420 engines (M116) didn't have them in early versions, and the headbolts could sieze. The threads will come out with the bolt.

Doing the inserts requires a special jig to get the angled bolts correct, so this really isn't a DIY project -- costs about $1500 last I heard.

Shouldn't be a problem on anything after 85.

Peter

[Roncallo]

Some good suggestions here. The only thing I'm concerned with is getting to that last head bolt and swinging the torque wrench 360 degrees without any increase in torque. I'm sure we all know that burning sensation. If its only the older engines that dont have inserts than I should be fine since I have a 560. I also dident realize there were bolts at an angle unless you are talking about intake manifold to head. But as far as jigging is concerned for that I do have a Bridgport Milling Machine. My intent for the head bolts was to make a jig block out of a pice of steel with a hole on each end, one as a drill guide and the other as a tap guide. I had no intention of doing manifold holes unless necessary.

Thanks
John Roncallo

[CzarFC]

The holes that correspond to the bolts that go through the cam towers are at a funky angle.

Did you pull the block or are you working on it in place?

[Roncallo]

I will be working in place (I hope). Head bolts at an angle put a whole new prespective on the job. I could imagine doing this job with an old junk head as a jig preferably with the head bolt holes sleaved with steel if you wanted to re-use it. Since I dont have an old head I will try to avoid the helicoils.

I will let you all know how I made out probably some time after the holidays.

Thanks All
John Roncallo