Crack in cam shaft cap

Yep, it was just going to smoothly to be true. I had the regular gremlins while reinstalling my cylinderhead today but daddy gremlin has arrived. On the top of the exhaust inside camshaft cap there is a crack. I doesn't affect the journal section. It is on top where a fitting has been inserted. Nothing attaches to the fitting so I assume it is for factory milling of the cap. I could install it and wait for a new one or rob one from my old engine. Anybody got any ideas on this?

 

Go to the Autoparts Store and get a strip of Plasti-gauge. Use the Plasti-gauge strip to determine the clearance between the Bearing and the Bearing Cap -- on one of the ones NOT cracked.

(The Plasti-gauge is fine filament that will "Crush or deform" when squeezed between the bearing and cap. When its crushed-flat ... the flattened filament can be measured against a scale printed on the Plastic-gauge paper envelope. The measurement is accurate. The product could not be simpler to use. Cut a strip of Plasti-gauge and lay it across the bearing. Put the cap on and torque it to specs. Undo the cap, take the flattened Plasti-gauge and hold it to the printed scale on the Plasti-gauge envelope. Read the clearance between bearing and cap.)

Compare the indicated clearance to the clearance you obtain testing the clearance on the bearing salvaged from your spare engine.

If the resulting clearances are the same (likely) ... or within the same measurement panel when the clearance is determined on the Plasti-gauge scale ... then,

Use the one not cracked.
Don't place any faith in cracked aluminum.

 

I'll back you up on that one Rick. Hope you find a decent cap off the old motor Max. Best of luck to you.

 

Hi Jeff ,,Give me a call and i'll help you on this one..
Steve

ps..My # is in your PM box

 

I was going to say that a last ditch effort would be to weld it, but this would be a terrible idea. It would probably warp the cap, so that you would have to remachine the bearing surface.

Sorry to hear that!

 

:!: Well I stole the cam cap from my other bike and first checked it with plastigauge on the old engine. It was within tolerance. Then I moved it to my current engine and checked it with plastiguage. Still within tolerance. So the engine is back together as far as lower and upper. Timing has been checked and is still spot on after two revolutions of the crank with the needed 19mm wrench. Thanks for the help guys. It's times like these that you can loose objectivity. My heart sank when I saw that crack. I will try to take pics of it with the camera at work and post them.

 

Keep spinning the wrenches. You never know when you'll be able to jump-in and help somebody -- yourself!

Plasti-guage is a fun product ... huh?

 

Yea I like that plastigauge Rick! Got the answers to my questions also. Some time ago I had a valve cover bolt strip. It didn't leak and I was just going to wait until winter and do the helicoil thing.
Remember the insert on the top of the cam cap that I figured was for factory milling? Well that is what the inside left valve cover bolt screwed into. So that's how I cracked the cam cap. Mind you, I put these in with a torque wrench! So I dropped the torque setting down to 5 ftlbs. That also explains the question that has been bugging me all day; how did I miss that before? Because it happened last time I put the valve cover on so I couldn't have seen it. Not without x-ray vision!
So now I know what the valve cover bolts to. 8O I also have used plastigauge for the first time and will study this sweet little invention further. 8) Tomorrow I will put the carbs back on and then the headers. Thanks again guys, this was quite an experience. And many thanks for answering my post, I still haven't heard a word from the xj-owners mailing list.

 

On that torque wrench...

What is the torque range?

I have always heard that the wrenches are very innacurate at the end of their range. I looked for a specialty wrench for very low torques, and couldn't really find one. So, I just do all of my low torques by feel. Not the best, I know.

Does anybody have a suggestion for wrenching all of this aluminum? Any good torque wrenches?

 

I have a snap-on wrench that ranges from 40-200 inch/lbs. Anything under 40 inch pounds is just rediculous anyway.

 

Been stripping engines and rebuilding since I was a little tacker. Torque wrenches for me are only for head and crank bolts.

Everything else is done by the hand of experience.

The thing to be wary of with torque wrenches is the false readings you can get in some circumstances. (head and crank bolts included).

Clean threads is the key to successful torque.

Always make sure your threads (bolt and casing) are clean. Always lightly lube threads for free movement.

Use air to blow out casing threads. Oil or water in a closed thread casing can cause compression and incorrect torque values.

ALWAYS check your torque wrench before taking it to your soft alloy motor. This may simply be sticking a bolt and nut in the vice and checking that it clicks.

When working on alloy casings, set your torque wrench low for a first pass and then follow up with a final setting.

Torque wrenches are handy tools but if used incorrectly they are your worst enemy.

Cynically
HG

 

Don't have the wrench with me but it starts at 5 ftlbs and goes to about 80. The setting for the valve cover bolts is 7.2 so I am at the low end of it's spectrum. A torque wrench in "inch" lbs would be the best solution on these aluminum engines. I have no idea of the cost but after this little episode I am going to look into it.

 

Please let us know if you find a good deal!

I have been wary of buying used torque wrenches because they are sensitive equipment, and who knows how the last guy abused it.

I can't find a good cheap one! I have the Harbor Freight for the big stuff, but nothing for the little torques.

 

Completely with you on the last statement HG. Snap On has an excellent little guide that comes with their torque wrenches that illustrates proper technique. Should you need to run some low value torques, you should obtain a wrench that will have your needed values that fall more or less mid-range of the wrenches capacity. I've tested and used Harbor Freight cheapies without trouble. Word of wisdom is to have them tested before you use them (I get mine done yearly). Good luck!

 

So where do you get your torque wrench calibrated? I would love to check mine. Can I just go to a Snapon dealer and have him check it?

 

one tip you can use to fix your stripped bolt. I think I know which cam cap you cracked. Its most likely the ones right next to the cam chain. What you can do is take the cap to a machine shop and have them make a ring that will press on to the outside of the cracked post. Then you can helicoil it and you will never have a problem with that again. One thing that everyone needs to remember when replacing caps or finding a really trick head in the junkyard is that the caps have hollow dowels in them. The cam caps were line bored when they were made. Everyone of them is different and you can not simply go to a dealership and ask for the intake cam cap.
Hope that helps and hopefully it didnt confuse anyone
Sean

 

Great post! Since I didn't know how they were manufactured I went the plastigage route. So it seems that is the only way to go. I checked the clearance on the old engine and it was toward the loose side, .051mm. Same cap on the current engine was well under that. Somewhere around .02. Package doesn't have the markings for the smaller clearance. Needed the green strip but could only get the red.

 

The Old School Method

You'd rather have to tighten a non-critical fastener (like the man said -- Mains and Bigs) ...

you'd rather have to tighten it a dozen times ... than break it once!

Rick Massey

 

There are contact points for SnapOn, Sears, Mac, as well as local calibration facilities locally if you live in a large metropolis. Should be a few bucks but well worth it. Make sure you get a read-out of the test, it will tell you what percentage to adjust for throughout the range of the wrench. Best of luck to you!