Help! Cracked Cam Cap

I was torquing down my valve cover with a torque wrench set to the proper torque and my exhaust cam cap cracked! (See attached image). From what i am reading it sounds like i'm going to have to get an entirely new head. Is this true? Does anybody have any ideas on how to fix this?

 

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To make you feel better NO you dont need a new cylinder head . Get on ebay and find a exhaust cam cap and be done with it

To make you feel better NO you dont need a new cylinder head . Get on ebay and find a exhaust cam cap and be done with it

 

I read that this was a bad idea as the cam caps are machined for the specific head

I read that this was a bad idea as the cam caps are machined for the specific head

 

They are

Cap and head are a matched set. You can get a used one machined to fit. The head gets pulled. Valves and all hardware removed. Cap fitted, bore honed and cam clearance checked. Then cleaned, reassembled and off you go.

 

No need to torque valve cover bolts. Tighten till bottomed and then just a tiny bit more. There is no give in them. The special bolts shoulder bottoms against the cam cap.

That cover bolt is 7mm.  I suppose some torque table says 10 ft lb.  I sure do not advise that.  Snug tight is fine.  Dare I say it? I hate torque wrenches, cause more problems than they solve.  Torque wrenches are fine if the user understands their limitations, what is the right tool for the job, properly set, in calibration and the torque specification is reasonable for the application.  So did this torque wrench have a scale in the range of say 5 to 20 ft lb? (60 to 240 inch pounds)?  and in my experience 10 ft lb (120 inch pounds) is too much for a 7mm shoulder bolt into a soft alum cam cap.  Tech manuals are written by tech writers that may not know much about what the job really is.  They get standard torque values from a table without knowing where the torque is used.  Too many examples of bad or just incorrect info in the official Suzuki service manual copied and repeated in other brand manuals.  I know you tried to do everything right but inexperience and bad tech information worked against you.  I can see the bolt has been overtightened on many occasions.  

 

The crack is not too bad, it can be weld repaired.  The critical cam journal surfaces are well away from the area that needs weld.  Bolt the cam cap to a sturdy flat steel plate (3/8" to 1/2" thick) use all 4 bolt holes.  That will hold the shape of the cap.  Then find a welder that can weld up the crack and the stripped threads.  A machine shop will have to drill and re-tap 7M 1.0.  If you continue to use a torque wrench, use a 100 inch pound wrench and torque to 60 inch pounds.

The threads are damaged. Will a machine shop be able to fix the damaged threads so that they are reliable and strong?

Yes.  Assuming the welder does a good job of cleaning out the old threads and welding up the hole.   Your welder will probably choose to use 4043 filler.  The deposited weld metal will be more or less the same strength as the die cast cap.  Pretty soft but adequate for the purpose.

 

Another approach is to just weld the crack and repair the thread with a Helical thread insert.  Problem with that is not much material remains in the boss the hold the thread insert.  I would try to fill the hole with weld and recut the original size 7M thread.  Talk to your welder and machine shop for their advise before you choose a repair process.

 

A third solution is to shrink a sleeve around the boss, no weld, repair the threads with an insert. Problem with that is the boss is not round or straight to start with so some machine prep would be needed to start with.  Again talk to a shop and see what they can do for you.

Ah that sucks man, especially since you were torquing to spec. I always just tighten everything down, and go a 1/4 turn or 1/2 more on the cam caps and valve cover (using alan wrenches). I could see how you could easily over torque those caps or the valve cover with a torque wrench, since they don't need much tightening to be at spec. 

To make you feel better NO you dont need a new cylinder head . Get on ebay and find a exhaust cam cap and be done with it

Not unless he plans on line boring the new cap to fit the head.. They are a precision matched set. 

Can you just bolt one and go... sure... people do all kinds of ill advised things with a motor... then act surprised when they fail spectacularly or with a wimper soon after. 

The threads are damaged. Will a machine shop be able to fix the damaged threads so that they are reliable and strong?

A decent Tig welder can likely plug weld that boss, and then have it drilled and tapped. Its not a critical part of the cap.. just a retention point for the valve cover. 

I've had a similar issue, before knowing my ways around the DRZ engine (never had a 4-stroke before). I tightened the cam cap bolts to spec... And then ended up pulling out the bolt with the aluminum threads attached to it.

 

In the end I ended up tightening the bolt hand-tight (more was not possible due to lack of proper threads in the cylinder head) and glued it in with medium-strength thread lock. I am totally not proud of that and I really wondered whether it would work, but it's been running strong like that for 1.5 years / 15,000 miles now...

i didnt know you cant mix cam caps.. i have 1 swapped in my engine now..

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Could've been worse

Update: I was able to have a machine shop weld the crack and insert a new threaded insert. It is not the prettiest, but it works!

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That's great news. The valve cover doesn't need much to seal so it's not like that weld will be taking a lot of pressure or torque. Glad everything worked out and it didn't cause you many headaches and sleepless nights lol.

Cool, that was fast. Glad it worked out.

Update: I was able to have a machine shop weld the crack and insert a new threaded insert. It is not the prettiest, but it works!

Looks nice :-)

 

I fixed one of mine with a Helicoil and it looks far from as nice as your fix

 

Drop the torque wrench next time, and use "finger tight" one the tree bolts on the valve cover.

To make you feel better NO you dont need a new cylinder head . Get on ebay and find a exhaust cam cap and be done with it

Nooooo! Just cuz it could work doesnt mean do it! Try having it tig welded and re tap it. Ive been in your shoes, I have a head to send out to be welded as well.

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