look for nail polish marks on the case and cam sprokets. But the really good hacks hide their method by cleaning off the nail polish with brake cleaner.
The video of the sprocket shows it moving freely in and out, and the pin is not visible. Seems it came loose, stopped the belt.
Those are harden dowel pins that take shear. I see people all the time forget these or loose these on flywheels. Then they go boom! I wonder if a knuklehead lost the pin and put something else in there that sheared off? I don't see how the bolt can loosen and the pin be lost and the cam sproket still be on the camshaft.
Just to be clear, I am not an expert and these are just a questions from my own curiosity: With a properly torqued bolt holding the sprocket on the cam, does the dowel pin carry a substantial load? Would the friction between the sprocket and the cam, generated by the bolt holding it on so tightly, carry most of the load? If they did find the dowel to be snapped, would an under-torqued bolt be plausible explanation for the reason the dowel snapped (vibrates and rattles around then eventually snaps)? Like I said, no expert, just curios. Best of luck getting that 355 back on the road! David
The pin takes no load when the bolt is torqued properly. Once a bolt works loose anything is possible but I see no way to shear the pin off just by the torque of rotating the camshaft. If the pin was in place on assembly there will be plenty of physical evidence showing where it was when/prior to it exiting. I have photo's of the last misplaced washer found on a customers car, I will post so you know what you might be looking for. ""My plan is to at least have a qualified tech there, or maybe pay to have it opened at another shop with the original guy watching. "" I suggest this be discussed and agreed to prior to anything coming apart. Find the least abrasive situation and allow those in question the oppertunity to correct their mistakes in a professional manner. You always have the option of legal action but only the lawyers win at that point. "At cost" is not satisfactory if there was an obvious mistake made. Entering into this the attitude/mood should be 'all I want is my car fixed properly and in a very timely manner', anything else will just cause un needed friction of which no good can come.
I just asked cause I was surprised that you said that it cost you several grand more to change it cause the engine had to come out... I changed mine last month in half an hour. The only thing that had to go out was the engine hood.
Hey Brian and Dave for that matter. What do you guys think about the OP asking a qualified tech from elsewhere how much he would charge to simply come out and inspect the parts as they are exposed? If the original mechanic is willing to tear down the engine without charge and he could work it out on a Saturday or something I know I would be willing to pay a qualified expert like you guys the going rate per hour to spend a few hours looking over the take down after the engine is out of course but before anything internal is exposed or removed. That way no chance to hide an error by the mechanic and avoid the second mechanic cost of a total tear down with no idea what the outcome would be. Just my thoughts!
You or someone came up with that idea earlier. Something I was getting to in a round about way and Dave came straight out with it was avoiding stepping on anyones toes. Inviting in an outside mechanic can be like inviting in an outside woman. In this case even though the shop is agreeing to fix it they seem to be looking for a way out. I think it is important to do everything possible to not alienate him but to develop undisputable proof he F'd up. Your idea is not a bad one IF the current shop owner can be made to be agreeable.
What you say makes perfect sense. This is a tough one because it is hard to not seem untrusting of the original mechanic. I kind of over looked how he might react to being under the microscope so to speak.
FWIW, I can propose another possible failure mode --- It could be that everything was done correctly (belt handling, timing adjustment, hardware assembly, fastener installation, etc.). However, during assembly, a small piece of debris or foreign material may have been inadvertently captured between the mating face of the cog and the mating face of the camshaft flange. This would of course cause the cog to "wobble" about its axis during rotation ---- the amount of wobble could have been so slight as to be visually undetectable during hand cranking, idle speed rotation, or even possibly high speed rotation. But, the vibration and eccentric loading (amplified by the belt loads) this would place on the bolt and bolt head could have been substantial enough to loosen, and back out, the cog bolt (even though it may have been properly torqued) over time of use. I have not seen this happen on a car engine, per se, but I have seen it happen several times on industrial machinery using similar belt / pulley drive systems. So, when you have whomever disassemble and inspect your valve train; have them also look for witness marks or residue on the flange and cog faces. Obviously, if this is what happened, it was the fault of the shop (tech) who performed the work for not ensuring the cleanliness during assembly.
BTW, (and assuming nothing broke before it loosened) this is another good argument for why Ferrari should go back to using locking features on their cog designs --- why they ever abandoned this design principle still perplexes me... And, not using locking features on critical rotating machinery is, and always will be, VERY POOR design practice. Not using them NEVER "flies" in my world
Locking features? They NEVER come loose when installed correctly. The locking features you speak of are not used by anyone in the auto industry and will never prevent sloppy assembly work.
Thanks guys, good to be back. David, The possibilities are endless. I have taken apart engines where after 5 years there is still zero clearance between the tensioner and the arm with the belt tension still reading "high C", some folks have a hard time with instructions. In that case the tensioners are beat to hell and gone, rusty as the dickens at the contact point.... there is always a tell tale, sometimes you have to search hard but its there. You can only imagine the bearing side loads that engine experienced. I have another engine apart now with near the same. Tighter isnt always better, good photo's will tell the story.
Tighter is better and crossthread is as good as loctite? Wait until I post the pics of some of the $h!t I've come across lately! 10 of the 12 engine cradle frame thread inserts stripped...and flaps cut in the frame so they could put nuts on the backside for starters.
On this one, I wouldn't have been surprised at all if they would have just welded the cradle back into the car. Well, now that I think about it, I'm certain they would have, but they got to a point where they stripped every nut and bolt and broke parts and finally gave up and left the mess for somebody else to clean up.
Brian, For sure, nothing protects fully against poor workmanship. That's kinda my point I'm also thinking of something as basic as the locking tabs used on the 308 cog bolts --- at least they prevent the bolt from backing out more than 1/8 of a turn or so......... of course by then, it's loose --- and potentially too late...if the loads continue to be applied.... And, yeah they don't use them on the cog bolts, but cotter pins, thread-lock, and swages (axle nuts, e.g.) are used all over the rest of most cars ---- at least these provide some degree of retention, if not locking.
Dave, Where have you been? How have you been? I left Boulder a couple years back, so I don't get to walk over and pester you at your shop, anymore
I agree with this idea. Talk to the original mechanic, and politely explain that it is a good idea to have a neutral party do the teardown and inspection and to offer his opinion....with the original mechanic there to witness everything. This will rule out the "conflict of interest" factor. Love this quote
If that bolt is not correctly fastened it will break the indexing pin. I have seen it happen. The pin is not strong enough to take the shear load. A lock tab, safety wire, locktite, crimp nut, you name it will not provide clamping force. Clamping force is all that will do the job and proper torque is all that will provide that. The others just make it easier to find the debris.
