M42 Head Gasket Replacement

[iamsam]

I am making this thread because I want to kill a myth that seems to be running rampant on the forums.

You do NOT need to remove the cams to remove the head of an M42.

I am honestly unsure why every writeup I have seen says to remove cams. The head bolts are obviously designed to be accessed with the cams in place, and dropping a 3/8" torx and extension in there is about as easy as dropping in a spark plug socket to remove spark plugs.

Here is the original thread I made with a few pictures:

http://coloradorallyracing.com/forum/viewtopic.php?f=3&t=89

[KenC]

I've done about a half dozen of these and I've never removed the cams... I've never even thought to. You do have to be very careful, however, to not drop a bolt washer down under the cam trays.

[iamsam]

I've done about a half dozen of these and I've never removed the cams... I've never even thought to. You do have to be very careful, however, to not drop a bolt washer down under the cam trays.

It's true. I did have to hunt for a couple washers for quite some time.

This is my first time doing an M42 HG, and as such, I did my research, and all my research told to to remove cams, but when I got in there, it was obvious that the cams do not need to be removed.

I have seen threads where people fabricate holding blocks to keep the cams both on TDC, which seems completely useless to me, since the cams don't move even if you try moving them (I did).

[Ryann]

I found more write-ups with instructions to avoid removing the cams than otherwise when I researched my HG/PG project.

[iamsam]

I found more write-ups with instructions to avoid removing the cams than otherwise when I researched my HG/PG project.

interesting. I searched R3V and M42club only, though.

[KenC]

The pressure of the valve springs will move the cams away from TDC when you release tension on them by removing the cam gears.

[iamsam]

The pressure of the valve springs will move the cams away from TDC when you release tension on them by removing the cam gears.

I was actually afraid of that, but I think in my specific case they didn't move because only 4 of the 16 valve springs were compressed.

[Massimo]

My torx socket didn't fit so I had to remove the cams. But yeh I don't know where the idea that you must remove the cams came from.

Plus I need to replace my lifters.

[Simon S]

+1 on not having to remove the cams. A parts-store torx socket fit/worked for me.


Also, fwiw – I used a VR gasket and VR bolts – then followed the procedure of torque spec, +90, +90.

The last 90 took a scary amount of my strength – like most all of it with use of breaker bar.

After two fair heat cycles – I pulled the valve cover and found at least half the bolts able to cinch down tighter per the amount of strength it took to initially get that last 90.

I think the ARP stud instructions include a similar step after two heat cycles (re-torquing).

I believe VR gaskets get a bad rep because those bolts do indeed stretch/expand/shrink/loosen – and nobody thinks to retorque them after some heat cycles.

So far, my VR gasket/bolts are leak-free.

[Ryann]

^I used VR stuff as well, ZERO issues.

[Massimo]

Hmm I used victor rans bolts or what ever that name is, I haven't checked to see if they are still tight might do that tonight. Other then that no issues, +1 on that last 90 degree turn I used my 500mm breaker bar and it was still a hard. I think if I ever do it again I might swap over the ARP studs instead. 2 or 3 of my bolts seemed as though they over stretched on the last 5 degrees, but I just pretended that didn't happen and have had no problems since.

[Mr.SWISS]

If you boys had a hard time torquing factory stretch you are not man enough for ARP's.

Eat some Wheaties while you save your $$.

[iamsam]

So Simon, you mention re-torquing the bolts after a few heat cycles, what exactly to you torque them to? You couldn't possibly turn them another 90 degrees, could you?

And regarding manliness and strength required to torque these, I just used a cheat bar and it was easy to do 90 degrees twice. They didn't feel like they were going to break to me. Those bolts are SUPER strong.

[Simon S]

So Simon, you mention re-torquing the bolts after a few heat cycles, what exactly to you torque them to? You couldn't possibly turn them another 90 degrees, could you?

aw, jeeze – I was afraid someone would ask me that..

The manual procedure on the torx (E12) bolts is:
Stage 1 … 30Nm (22ft-lb)
Stage 2 … +90°
Stage 3 … +90°

Torque order per view from passenger side of head:
7__5__1__3__9
10_4__2__6__8

Because I’m so anal – I waited 20-30 minutes between torque stages. I think this was another ARP stud instruction-inspired step that I added.

Over the years of working on bikes and cars – and torquing down various bolts – I just acquired the feel needed for most nuts and bolts per what size they were. Don’t get me wrong – I totally believe in use of torque wrenches. I used mine for stage 1.

When I say it was “scary” – I meant that that last 90° crank took a remarkable amount of strength to get. It wasn’t like I had my foot up on the fender – but the force needed ‘concerned’ me since the head bolts themselves are like 1/4" thick and as long as they are.

..and snapping a head bolt was the last thing I wanted to do. My last turns were more like 80° - just to be on the safe side.

Call me crazy – but I noted the amount of strength it took to do the last stage.

After the 2 heat cycles – some of the bolts were fine. I put my ‘measured’ strength on them – and they didn’t budge.. but most of them easily took another 10-60° of turn on them.

What I did there was judgement-call and feel – not something easy to put into a procedure. The factory procedure doesn’t provide a “final” torque spec – so I went rogue and did what I felt was right.. much inspired by ARP stud instructions.

Take my input for what it’s worth. I can tell you that if I worked at a shop and was paid hourly – there’s no way in hell I would have put this amount of love, care, and thought into a procedure like this. I really let my OCD run rampant on my project – head installation included. I’m not saying it’s the best way – I’m just saying it’s the best way I knew how – with what tools and knowledge I had at the time.

[Mr.SWISS]

. Those bolts are SUPER strong.