Camshaft stopped!!!

[BugEyeBear]

MIGHT BE WORTH NOTING what series of motor (manuf, serial #, build date, etc.), and what type of damper, and what type of cam is involved in these failures!?!

I'm not sure if the parts involved have any identifying numbers in them (or distinctive features/markings), but it WOULD be good to know if there is a trend out there.

(for example, Mazda Miatas had defective crankshafts in the very early engines, so these are avoided by guys looking to restore or race...)
Miata Crankshafts

Even engines with very reliable reputations can have defects....

 

[stumps]

I agree!

But I can sympathize with one's wanting to determine if damage has occurred BEFORE pulling the head off or the engine out.

(I rebuilt a "bad" transmission once, only to discover later that all it needed was a new pilot bushing...) "DOH!"

-Bear-

Transmissions are an entirely different beast.

Sadly, we can sympathize all we want, and he can diagnose all he wants, but there is really no point (to the later). If the camshaft stopped turning and the crankshaft didn't, there is damage too great to fix without removing the heads, and dropping the oil pan. It's a fact we must live with here in overhead valve compression ignition engine land.

It goes like this: If the cam is holding any valve down when the piston reaches TDC, you will have a bent valve, and a bent push rod... minimum. If the valve head breaks off, it usually falls to where it cannot move out of the way, and you will have a bent piston rod, broken piston top, and often a twisted/broken crank.

Sorry to be the bearer of bad news.

The heads need to come off, and the oil pan needs to be removed.

-Chuck

 

[badgmc56]

First of all, not every overhead valve motor is an interference motor. Just one example, and there are many, is the Ford 300 six with the fiber cam gear. The reason why I know this is because the fleet of 150 vehicles that I am in charge of has 9 vans with these motors in them. They have over 200000 miles and the cam gears have been replaced more than once in each van. They come in not running and the camshaft not turning. We have NEVER had to pull the head because of bent valves. I would first find the cause of the camshaft or keyway failure and then go from there. DO NOT start ripping the whole engine apart before you know EXACTLY what is wrong with it. Even if the valves contacted the pistons and the heads have to come off does not mean the pistons are bad or the rods are bent! I have done probably hundreds of timing belts and timing gears that have let go , alot being interference motors, and can't ever remember having to replace bent rods or pistons. The moral of this story is do a acurate and complete diagnosis of the problem before you rip too deep into your engine and your pockets!

 

[WillWagner]

Unless you have money to just spend aimlessly. Find out what happend. These are made to be repaired in chassis.

 

[stumps]

First of all, not every overhead valve motor is an interference motor. Just one example, and there are many, is the Ford 300 six with the fiber cam gear. The reason why I know this is because the fleet of 150...

I'm sorry, I was imprecise. I should have said: "overhead valve compression ignition engine land. " I will edit my mistake.

...And because of your experiences with the I300, with its 8.0:1 compression ratio, you think the 22.5:1 compression ratio multifuel engine will be not have bent valves, push rods, or piston rods???

-Chuck

 

[WillWagner]

I just thought about this. On these engines, the piston has small chamber in the top. That means the valve hits squarely on the piston, unlike the NHC. Most of the time in engines that have this type of piston, the valves don't bend, just the push tubes, that's the weak link built into the design. If the cylinders hold air, there should be no reason to yank the heads. If it were mine, I'd check the cylinders and if they held air, i'd slam a cam, pushtubes, tappits and a damper on it and let it go. When the pan is down for the cam job, you can check rods then.

 

[badgmc56]

Stumps, My point AGAIN is this, make sure you know what is wrong and how it happened before you tear and engine down to the bear block! Could the valves be bent? Sure they could and they probably are. That would be the first step in the repair process. Too many times I have seen guys disasemble a motor before even spending an hour checking it out. In those cases guess who was footing the bill? The poor guy that trusted you with his vehicle. In my shop, you have to prove to me with facts that a total disasembly is in order. In the repair business you must take a very good look before you go crazy with air tools . We are not always right every time but we sure try to be. Sometimes, when you have exausted all other options, then you need to START taking things apart to inspect. In certain situations that is the only way to find the problem.

 

[opie65]

Step One: Pull Rad
Step Two: Pull Front Cover and look for Primary Failure
Step Three: Pull Injectors / Valve Cover / Intake and look for Secondary Damage with Eyes and Bore Scope.
Step Four: Based on what you find...

I don't expect that I got out scot free, but I'm not ready to just throw the motor in the trash and start over. Other than the grand scale, this engine is pretty easy to work on. (Besides, anybody can R&R an engine. I want to FIX it. Shop Credibility...)

If it is a Front of Cam Failure at ~ 25K and ~550 Hrs, that puts it in the same range as other ones here on S.S., and I would want to start a log of build dates.

 

[73X]

If you need help and are within a few hours let me know and I will load up and jump in.

 

[gimpyrobb]

I have some parts motors available. Let me know if you need anything.

 

[opie65]

I probably will... Thanks for the help! The teardown is going to have to wait a little, I have to get some work/house things done.

 

[stumps]

Stumps, My point AGAIN is this, make sure you know what is wrong and how it happened before you tear and engine down to the bear block! Could the valves be bent? Sure they could and they probably are. That would be the first step in the repair process.

I understood your point the first time. Now, understand mine. When a valve gets wedged between a raised cam lobe, and a fast moving piston, it takes a horrible shock. Hollow push rods bend, rockers bend or break, but they don't give up easily. The valve head metal is quite brittle, and even if the cylinder holds air, stress fractures are likely.

Let's say we take your advice, and put in a new cam, lifters, push rods, and rockers, then put the engine back into service. If a stress fractured valve head pops off later, it will stop the piston dead 1/2 to 1/4 inch from TDC, the crank will torque bend, the piston rod will bend or break, the piston head will fracture, the cylinder head will get a big dent or crack in it, and the whole engine is a big mess.

Popping off the heads, and replacing stressed valves, etc. takes about as much time as scoping all of the cylinders, air testing through the injectors, and checking that all of the pistons come up to the deck.... If you consider all the time you will spend replacing push rods, lifters, cam, etc. anyway, you are talking about very little additional effort to do the job right, and protect your engine from serious harm down the road.

On my engine, any valve that smacks a piston top gets replaced.

On your engine, do what you want. I can't see it from my backyard.

-Chuck

 

[radiogeek]

I have a '71 m35a2 with the LDT-465-1D. I was driving down the road at about 45 mph and engine quit like I pulled "fuel off" handle. Towed Deuce home (2 miles) with a Dodge Ram. My cam broke right at engine side of cam gear. 3 bent pushrods. I replaced cam, cam gear, thrust plate and pushrods per the TM on this site. I'm happy to say there seems to be no major damage to pistons, valves, tappits, etc. It started on 3rd try and she runs better than before cam broke. I suspect this is due to valve lash being adjusted after re-assembly. All work was done with engine in chassis and radiator removed. My very helpful wife made the repair quite easy. 16,9xx miles on odometer, plate says engine rebult in 1988. This was the first time I have worked on a diesel engine! Of course, it may fly apart on my next ride but so for, so good. Good luck with yours.

 

[velociT]

I have a '71 m35a2 with the LDT-465-1D. I was driving down the road at about 45 mph and engine quit like I pulled "fuel off" handle. Towed Deuce home (2 miles) with a Dodge Ram. My cam broke right at engine side of cam gear. 3 bent pushrods. I replaced cam, cam gear, thrust plate and pushrods per the TM on this site. I'm happy to say there seems to be no major damage to pistons, valves, tappits, etc. It started on 3rd try and she runs better than before cam broke. I suspect this is due to valve lash being adjusted after re-assembly. All work was done with engine in chassis and radiator removed. My very helpful wife made the repair quite easy. 16,9xx miles on odometer, plate says engine rebult in 1988. This was the first time I have worked on a diesel engine! Of course, it may fly apart on my next ride but so for, so good. Good luck with yours.

What kind of oil were you running?

 

[gimpyrobb]

Glad to hear it Radiogeek! Good to see you posting.

 

[radiogeek]

No clue what kind of oil was in it. It was pretty black. I changed oil & filters after re-assembly and used Mobil Delvac 15w-40. I bought the truck this last spring and did not know the maintenance history. I am keeping a log book now of what I do to it. It has been fun and an unexpected learning experience.

 

[73m819]

i have a '71 m35a2 with the ldt-465-1d. I was driving down the road at about 45 mph and engine quit like i pulled "fuel off" handle. Towed deuce home (2 miles) with a dodge ram. My cam broke right at engine side of cam gear. 3 bent pushrods. I replaced cam, cam gear, thrust plate and pushrods per the tm on this site. I'm happy to say there seems to be no major damage to pistons, valves, tappits, etc. It started on 3rd try and she runs better than before cam broke. I suspect this is due to valve lash being adjusted after re-assembly. All work was done with engine in chassis and radiator removed. My very helpful wife made the repair quite easy. 16,9xx miles on odometer, plate says engine rebult in 1988. This was the first time i have worked on a diesel engine! Of course, it may fly apart on my next ride but so for, so good. Good luck with yours.

lucky