I bought a 1993 Dak LE 3.9, 5 speed from the original owner about 6 months ago.
Had over 330,000 miles but well kept/maintained. He had any/every maintenance receipt it had done on it (even wipers and light bulbs).

His last Timing Chain change was 80,000 miles from current. It had the TC rattle when I bought it but figured it wasn't that many miles on a TC. Well I didn't know Dodge Magnum Engines that well.
So I put off the TC change too long. One day I pulled in to get gas, filled her up. Tried to crank her up and it just spun over really fast and a lot quieter than normal. After several more failed attempts I had it flat bed towed home.

Yesterday I took it all apart and took off the TC cover and found the issue. TC was stretched bad of course. The top large sprocket was worn bad. I turned the crank with a ratchet a bit and the TC was jumping the teeth on the upper sprocket. Lower small sprocket looked like new. And it was even a double sprocket/TC set. Also, I removed the 3 spark plugs on the drivers side, the middle plug had slight damage to it (the electrode was pushed and bent over to the side). Gotta check the other 3 plugs.

So here's where I need some helpful info and good advice.
1) Is it possible to know, or is there any way to check for damage to the valves with the cylinder heads still on the engine? (I read something about compression checking to do so??) It didn't sound like anything was hitting when I was trying to start it that day, but I realize the damage can happen quickly.
2) Also, how would I get the cylinders back into proper timing with the valves, as far as each cylinder with it's set of valves, and on intake/exhaust?
3) Are the Magnum engines non interference or interference (valves and pistons can hit if TC fails)?

Would getting it all back into proper timing and putting on a new TC set and just going for it be a bad idea? Or should I check the valves completely? And if so does that mean removing the heads?

I have a Haynes repair manual for it and doing lots of research on it. Just can not figure out how to get the pistons back in proper time with their valves.
Thanks in advance for any helpful info or advice.

Added: Pulled the 3 plugs from PS and all 3 are fine.

 

Compression test will tell you if you have a problem, but, gotta have a good timing chain, and the engine reassembled for that. Another alternative might be a bore scope. You can get them pretty cheap on Amazon these days. That would let you look at the valves without having to do any other work......

 

Appreciate the info. That was my plan to try first, Get a new TC set and put it all back together and then do some compression testing.
My main problem with that is I haven't found out yet how to properly (safely) go about getting the pistons back in sync with their valves. (Beings my TC was slipping as I was cranking it over I'm sure they are out of proper position). I don't wanna damage or make it worse than it may already be by rotating the crank shaft to get the right piston to TDC not knowing where the valves are. I'm not even sure if the valves can hit the pistons on this engine.
But I'm searching for the answer. I'm sure it's doable, just wanna make sure how before I proceed.

Also, I pulled the other 3 plugs today (passenger side) and all 3 are fine. So only the middle plug on DS has a bit of damage. I will try to post a pic of it.

Thanks

 

I'm not sure I understand how the valves can be out of sync unless the cam was moved independently from the rest of the motor. I hope this set of instructions will help you determine if you valves are in sync with the pistons.
http://www.bionicdodge.com/Download/...uel%20Sync.pdf

 

[QUOTE=onemore94dak;3388348]I'm not sure I understand how the valves can be out of sync unless the cam was moved independently from the rest of the motor. I hope this set of instructions will help you determine if you valves are in sync with the pistons.
http://www.bionicdodge.com/Download/...uel%20Sync.pdf[/QUOTE

Thanks for the link, great info.
My thinking was that when I was cranking the motor (crankshaft/pistons rotating) and the TC was just slipping on the cam shaft sprocket, that would have put the pistons and valves in a different position than where they should be?? Also not sure what hit the spark plug to bend the electrode??

Trying to figure out how to get the pistons back in time with the valves. I'm assuming I'm going to have to turn the crank shaft and cam shaft seperatly but I don't want any of the pistons to hit the valves in the process (if possible)??
I've read that these are interference engines and damage can happen if the TC breaks. Mine didn't break, but it slips. Did try cranking it under these conditions so it's possible there's damage??

Gonna get a bore scope camera and inspect inside the spark plug holes (cylinder) and see if there is any obvious damage. If not I will get a TC set installed and put it back together and go from there.
My problem, due to lack of knowledge on it is, I can't just install a TC set and put it back together. I have to get the #1 piston to TDC (I can handle that, have a repair manual) and the cam shaft needs to be rotated to get it to match the crankshaft (12/12 or 12/6 from what I'm reading). I want to make sure the valves are not out of time with the crank shaft when I put it all back together.

Appreciate the help and patience.

 

With your new timing set in hand, just turn the crank, and cam, so the dots on the gears line up. That *should* be all you need to do.

 

This.

You turn by hand so you can feel if they hit; and once the dots are lined up, it's in time.

RwP

 

there are "good" timing chain sets and "cheap" low quality" ones.... I always spend a few bucks extra for the "good stuff". but with 330K miles on it how long do you expect this engine to last? I see lots of relatively low mile 3.9s on Craigslist. buy one, regasket it, put your new chain and gears onto that engine and swap. be cheaper thana valve job and all new intake valves which is what will be needed if the valves and pistons made contact.

 

Appreciate the helpful info. I guess I'm being to cautious, and don't have a complete understanding of the valve system.
If I understand correctly, each piston will hit it's top out position in its cylinder at different times (6 different times)? What about the valves? Do I have to get the cam shaft in the proper rotated position so that the valves in #1 cylinder are in sync with the #1 piston when it's at TDC?

My concern is, beings the crankshaft turned and the camshaft didn't (when I tried cranking the motor and the TC was slipping), Isn't the valves out of position from the pistons?
Do I need to put just the old cam and crank sprockets back on (with no TC) and turn them separately until the dots line up (then put the chain and sprockets back on)?
If I were to put a new TC set on now and turn it I don't know if the dots would ever line up.

Yes I will only turn the crank shaft by hand/ratchet slowly. Now, What happens if they do hit, what do I do then?
Thanks


Attached a pic of the plug that was damaged. Pushed the electrode to the side and scraped the center electrode. Like a hit from an angle.

 

Here's how I'd do it. First, if you haven't already, remove the plugs and stick long straws or wooden shish-kabob sticks in each plug hole and leave 'em there. That'll give you a good indication of where the pistons are in their stroke. Next, remove the valve covers so you can see where the valves are in their cycle. Now, if any cylinder looks like it is near contact with it's respective valves, turn the crank sprocket a bit so that the piston moves down. The straw should move further into the cylinder; and you should only need to go a small distance. Watch the other cylinders as you turn to make sure they stay clear. Your goal is this: Noting where the sprocket dots are positioned, you want to move them toward each other, taking the shortest distance to the meeting point. If you back the highest piston(s) away from the top you may find a point where all the pistons are about mid-stroke. At that point you can move the cam into position, then start moving the crank into position, again watching the valves. If a piston looks like its going to contact a valve, back the cam a bit to get the piston past it. Should only take a time or two rocking the cam sprocket back and forth before the crank is positioned.

The straws/sticks may get crimped when the piston moves up, just watch 'em and adjust as necessary. It doesn't take a whole lot for a piston to bend (or break) a valve, I know, I've seen it done. Take your time and good luck.