Camshaft key

IA1456

Member
Looking for some imput
Have a 1206 with a 361 put back together from a major overhaul on Startup camshaft gear Key Sheared
Check my timing gears and they were in time camshaft turns free by hand what would cause that key to shear
 
I did and 7 of the push
rods are bent my
question is did the key
shear and throw it out
of time or did the
valves hit and shear
the key
 
I was getting almost 40psi of oil pressure when cranking it .
It Did sound like it almost started
 
Well check the rocker arms for clearance on the valves as you take it apart. You will need to be able to turn the cam for this so you know whether the valves will open with the piston up. IF there is still no clearance then the valves were to tight if there is clearance then if the head was shaved they probably hit the piston.
 
Well if you bent seven of the push rods then it was YOU that did something wrong , now how bad you messed up you will not know till you pull the head and look at the pistons , rods and rod bearings and the valves . This engine is NOT for the novice to be rebuilding and head work is NOT for a fly by night machine shop that does NOT know how to set the valve protrusion . There is NO clearance for the valve to clear the piston with the engine running and a wrong valve set done wrong can lead to total disaster . One other thing with this engine is that after you have installed the sleeves you MUST check the bore with a inside bore gauge for winking of the sleeve and look for cracking of the sleeve , each piston MUST BE Checked for size as they qare NOT all the same and be fitted to the bore . Had one guy around here that did not like my price on rebuild laughed at the local dealer on his price and went the DIY route five blocks later he shows up at my door step wanting me to build the engine because the best life he got was 35 hours run time before it made a new inspection hole in the blocks and totally trashed out the other five.
 
Something had to cause the key to shear like a load on cam. Bushing seize? Oil holes lined up? Guessing eng turned over by hand during assembly? Out of frame OH? Welcome to my world!lol
 
Tractor vet : I never claimed I haven't made a mistake but I'm looking for insight into what I did wrong that would make the key shear.
 
If it tried to start, and got oil pressure, and then went into the basket, stuck cam bearings, or a jammed oil pump could do it. If a BB sized hard piece got into the oil pump it will not turn. Does the cam turn? If it does not, find what is keeping it from turning. Jim
 
Like i said a wrong vale set , bad head job , were as they did not get the valve set to correct height and where as with this the head of the vaves were already to close to the piston and when you turned the engine over they made contact to that piston and thus causing them to be forced back closed as they were trying to open caused the push rods to bend and this cause more loading on cam drive and this is probable is why the key sheared . Now had this engine started to run you could have had valve failure along with a piston breaking maybe a connecting rod failure and coming out the side of the engine . Like i said the piston to valve clearance in this engine is real close . when you do a valve set on this engine it is done with the engine OFF and i don't care where you start the valve set as long as you know if you are starting at #1 at tdc or #6 at TDC you set the valves according to where you start from BY THE BOOK . and As long as everything on that engine is at or above 70 degrees you set to the spec. . You also must check how the sleeves set in the block for sleeve protrusion . There are two engines that plum scare me when rebuilding , one is the D361/407 and the other is any old 2 stroke detroit . when it comes to those i am way past ODC and i don't mean OLD CRANKING AND DANGEROUS . Everybody know i am old and cranky .
 
Your question on what came first can only be answered by further investigation, as either could have caused the issue. I would loosen all the rocker arms and turn the engine over by hand several times to see if something else is bound. You will probably have to pull the injectors to act as a compression release.
 
On ANY direct injected diesel there's NO valve room if the driveline fails. Loose a gear or key, valves WILL hit the piston unlike some gas engines. As tractor vet said, just trying to set rockers running which is a diesel no-no, that can cause them to hit too as both valves are that close during exhaust closing, intake opening overlap period. Neighbor's IH 414 combine engine lost timing gears last fall, all push rods bent, and all barrel tappets were broken on top besides the gears damaged.
 

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