Camshaft stopped!!!

[wilco]

Friends 1971 m35a2 deuce quit on the trip to the Grayling fall tour....
Crank turns and the injector pump pumps, but no valve action!
broken key or cam nose.
Is the turbo a interferiance engine/ ( Valves clear or hit piston)?
Made no bad noises when it died / cranks.
Is the hole for the injector big enough to get a bore scope in?

 

[Somemedic]

Sorry to hear. I'm gonna subscribe to see what the cause/remedy is.

 

[Westech]

Sorry to let you know but every over head valve engine is a interference engine. Just the engines that are called interference engines have a really tight valve to piston clearance. If you have a valve open and a piston where it is not spoz to be it will smack the crap out of it.

Now there is a good chance that the valves will be ok, but if a cam broke its not a good turn of advents for that engine. you should be able to scope that cylinder via the injector hole.

 

[FMJ]

Been there, done that, got the T-shirt. . .

http://www.steelsoldiers.com/deuce/28165-engine-shut-down-while-driving.html

 

[BIGdaddycatlin]

with the lack of bad noises id say theres a good chance that no damage was done to the valves but you have to wonder what caused there to be enough resistance on the cam to make it stop hopefully its not sized in the block or anything of that nature

 

[Keith_J]

OUCH! When the cam stops turning, pistons will smack valves. In a pushrod engine, the damage is limited to valves and pushrods. I see a new cam, tappets, pushrods and reworked heads, at a bare minimum.

Do NOT reuse any valve which contacted pistons, when you pull the heads, you will see the marks in the pistons. Those valves are stressed, if reused, they will cause far more damage, usually to the crankshaft.

Check piston projection when the heads are off. Bent rods and smashed pistons will not go to the same height. Measure and compare with pistons that have not contacted.

 

[BugEyeBear]

Reminds me of an AMC Matador that I had back in college... (yeah, I know, "A Matador?!?" It was a $200.00 car to get me around for a couple of college years... Besides, it was good enough for Reed & Malloy!! (the Adam-12 guys...))

This was an AMC V-8 with over 250K miles on it and it simply quit one day shortly after starting.
I soon discovered that the Teflon teeth on the cam gear had worn, become brittle, & broke off.
So I bought a new set of gears, a new timimg chain, a front cover gasket set, and went at it.
Successfully replaced the timimg set and the car started right up!
BUT, this gas engine now sounded like the noisiest diesel that you've ever heard!!
Obviously valves & pistons had played TAG, and more work was needed.
But being a poor college student my funds were already exhausted, so I painted "For Sale, $99" on the windshield and let the new owner tackle the next round of repairs...

We drank good beer for a few nights thanks to that car sale!
(& I rode the bus for the rest of that school year!)

 

[WillWagner]

How will the crank be hurt? If you reuse a valve that has been smacked with a piston, it CAN break the head off. When that happens, the rod could bend, then break, and worst case, you'll be re blocking or swinging an engine 'cause the block vents itself.

 

[roscoe]

Did he get the truck home?

 

[digitaldust]

ya i dont know much about the diesel were running but i'm off I75 exit 118 if you need help wile in MI let me know my number is area810then5773524 sorry it looks strange but bots will make calls to your phone number if it looks good and try to sell crap from the mid east ya ya ya

any how YES happy to help if i can I have a van with 110vac and Air tools etc .

hope all goes well for you
FLINT MI thru Midland Mi

 

[OKCMoparGuy]

I've seen a few keyways that weren't inserted completely. They usually last for a while before finally shearing. I think these engines are around 21:1 compression ratio......at TDC there's not much room for an open valve to hide if cam/crank got out of sync.

If you're lucky you just bent the pushrods. Pull them out and roll on a flat surface to confirm.

 

[cranetruck]

How much would a compression test tell you?

 

[WillWagner]

The valves won't be opening or closing 'cause the cam isn't moving. Easy way to tell if the valves are FUBAR is to take the rockers off, pull the injectors and put air in the cylinders with a rubber tipped blow gun. A cylinder that has everything in tact will turn the engine over with the air pressure. One that has a bent valve(s) will hiss out the intake or exh, or both.

 

[BugEyeBear]

IF the valves are bent enuf that they aren't closing all the way then you'll get low compression. BUT since your cam isn't turning you are likely to get low compression in at least half of the cylinders, even ones w/o bent valves.

& with the air pressure test suggested above it is worth noting that you'll want to pull the injectors on ALL of the cylinders & remove ALL of the rockers prior to testing. This will allow you to test each cylinder w/o getting resistance from the other cylinders. Otherwise you'll either get resistance from cylinders that are closed-off OR you could cause additional damage.

I would have to say that you aren't gonna really know what damage has been done until you start taking things apart and replacing broken bits. You MIGHT get away with just replacing the obvious parts, but I'd guess that you'll soon discover that more parts downstream are gonna need replacing.

IF IT WERE ME, I'd plan on removing the head to discover with 100% certainty whether or not the pistons & valves "played TAG". That way I would have a much better idea of what valves might be bent, what pushrods might be bent, whether or not the pistons are severely damaged, and whether or not bits are floating around in the combustion chamber.

Trying to short-cut the fix might end up causing more damage than you already have.

Past experience has taught me that there are no short-cuts if you want to fix it CORRECTLY the 1st Time!

That's MY 2-cents!

-Bear-

 

[wilco]

What caused it?

 

[Keith_J]

What caused it?

I would place a bet on torsional fatigue. The torque required to turn the cam is periodic, this gives rise to fatigue. There are also minor bending loads from each tappet (lifter) which add to fatigue. And then the helical gear mesh load on the drive side, compounded by the injection pump drive gear. All it takes is a little flaw to exploit the cyclical load, leading to torsional failure.

 

[WillWagner]

Oh yeah, if the cam broke at the nose, replace the damper.

 

[stumps]

There is no point in scoping the injectors, trying to run the engine on air, or any of that stuff. If your cam really stopped turning, all the diagnostic tests in the world lead down the same road... the one where the heads come off, the oil pan comes off, and you start to assess the degree of damage.

Save yourself a lot of wasted time and trouble, pull the engine, strip it down and see if you have enough left to rebuild.

-Chuck

 

[BugEyeBear]

There is no point in scoping the injectors, trying to run the engine on air, or any of that stuff. If your cam really stopped turning, all the diagnostic tests in the world lead down the same road... the one where the heads come off, the oil pan comes off, and you start to assess the degree of damage.

Save yourself a lot of wasted time and trouble, pull the engine, strip it down and see if you have enough left to rebuild.

-Chuck

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-

 

[opie65]

Interesting. Mine went at 25K miles and about 550 hrs.