Guide rails

[milterino]

I am going to replace the lower guide rails on my m117. The cd says to use a flywheel detente to hold the motor when I break the crankshaft bolt free. My question, could I just put a wrench on the bolt and give the wrench a rap with a hammer and what damage might I do by by using this "blunderbuss" technique? Milt.

[Tomguy]

Is there a reason you're replacing the lower rails? I'd advise against it - more work than it's worth unless your engine has about 400k on it. Those bottom rails are considered bulletproof.

[milterino]

I don't have an impact gun, may consider the pry bar. Tom, I am hearing an unpleasant rap, rap, rap at about the frequency of the engine revolutions. More obvious with no load on the engine. My mechanic said he thought it was coming from down there where the rails are located or possibly the oil pump. When I put a stethescope on the oil pan the sound is more noticible. Hope it's not bearings. So, lacking any positive direction I am going to investigate the rails. Milt.

[Cephallus]

Before I owned an impact gun, I removed crank bolts by removing the starter and jamming a piece of angle iron into the teeth of the ring gear, sort-of like ellington mentions above (but the proper size of angle iron, instead of a pry-bar, lets you do it without help). Then you can really lean on a cheater bar on that bolt.

BE ABSOLUTELY SURE THAT IT's SECURE, because you don't want to turn the engine backwards...

[Benzcrusher]

If you break something I've got a parts motor... That's a hell of a project...

[milterino]

Well thanks, that's good information. I see there is an "engine detente" for rent in the rental section so I will check into that. Will let you know how it turns out. Milt.

[rfitts46]

what is the issue with the motor turning backwards? I could assume doing the rails the chain has been removed from the cam sprockets. If the engine turns in either direction you could hit valves. Is it alignment of the cams to the TDC position?

[Cephallus]

I wouldn't assume the chain has already been removed when removing the crank bolt. That's sort-of at the beginning of the job.

The issue turning the engine backwards, of course, is the timing chain path.

[milterino]

I as well don't know why the motor can't be turned backwards. Perhaps someone could offer a short explanation. What is the "timing chain path"? Milt.

[Strife]

If a 116/117 engine is turned "backwards", I think it is possible to catch and bunch up the chain on the top of the tensioner arm, possibly causing a timing chain jump. At least that's what I saw when I did both my 116 and 117 chains (when the cam followers were out, of course). At the very least, if the engine is started that way, there would be a sudden "slap" as everything retensions - not good for the plastic guides. Clearly, the arm is designed to operate in one direction only.

[senorunimog]

You could always stick a screwdriver through a cam sprocket to keep it from turning. Thats what I dont on my 6cyls if I have to take of the crank bolt. Not exactly the most elegant method, but it gets the job done.

[milterino]

Strife, you used the word "arm" in your reply. May I ask what arm you are referring to? Not exactly on this subject but you mentioned taking out the followers. Did you have that special clawlike tool they refer to in the C.D. or is there another way to take off those followers. Appreciate all this help, Milt.

[OldMercs]

Get yourself a really big chain wrench and use that at the front pulley; this makes removal of the crank nut a one man job when used in concert with a large breaker bar.

[milterino]

Hey thanks Mercs. It looks like an irritating job getting that starter off. If I can avoid it I will look for a chain wrench. Perhaps could use it again as aswell. Milt.