Garage Storage Organization and Garage Cabinets

V8EATER · **? about 3.0 broken timing belt**

Hi,
A friend of mine just called to tell me about breaking the timing belt on his 2000 Stealth. He was asking me if I thought he would have an issue with bent valves ( he said he was turning "high RPM's" ). The only experience I've ever had with a broken belt on a 3.0 did not result in any bent valves, but the engine was idleing at the time. So, do you think his valves are toast?

turbovanman · 09:15 PM

SOHC-he will be fine
DOHC-valves are most likely bent. Its an interference engine so its a 50/50 gamble. Easiest way is to replace the belt and before he puts the rest back together, start it up. If it runs fine, he's lucky.

V8EATER · 06-21-2006, 08:04 PM

I'm really not sure if it's SOHC or DOHC. I'm 30 miles away and can't look at it right now. I didn't realize there were 2 versions of this engine, I thought they were all SOHC. Thank you for the reply!

V8EATER · 06-21-2006, 08:31 PM

CORRECTION: Car is not a 2000 model. It's a '94. In his excitement, he told me it was a 2000, but I got to thinking "there is no such thing". I called him back and got the correct year.

phantomrt · 06-21-2006, 08:49 PM

I've seen a lot of interference 4 and 6 cylinder engines survive broken timing belts/chains. There is a cam position in which all valves are closed, and this is where the cams come to a halt.
On an interference V-8, forget it, because there is ALWAYS a valve open at one time or another.
You can crank the engine by hand and feel for "dead spots" Since all the valves are closed, you'll be able to feel where a cylinder is no longer compressing or suctioning. I recommend by hand because you'll be able to feel the engine stop against a valve that might possibly be open yet.

If you're confident the valves are closed, you can turn the key and listen for the dead spots. If none, the valves are fine.

allmotor · 06-21-2006, 10:10 PM

there is NO such cam on a multicylinder engine, where ALL the valves are closed. there are positions where none of the valves are open far enough for the valves to hit... however several are still open some amount.

If you don't believe me, just pull the valve cover on your turbo dodge. you will see, no matter what postition you put the cam, there will ALWAYS be some valves open (even slightly)

phantomrt · 06-21-2006, 11:33 PM

Quote:

Originally Posted by allmotor

there is NO such cam on a multicylinder engine, where ALL the valves are closed. there are positions where none of the valves are open far enough for the valves to hit... however several are still open some amount.

If you don't believe me, just pull the valve cover on your turbo dodge. you will see, no matter what postition you put the cam, there will ALWAYS be some valves open (even slightly)

*scratch* *scratch* *thinking*

Lets use the turbododge engine for an example. When you remove the timing belt, and rotate the camshaft by hand, you feel strong spring resistance and then BAM the cam lobe goes over center and the cam snaps into a "relaxed" position. This is where I am referring to as where all the valves are closed.

I just re-did my timing belt two days ago because I had to look at my water pump. With the cam in this relaxed position, the engine is DEFINITELY making great compression and suction on all four cylinders. Even if the valves were SLIGHTLY open, would it require so much effort to rotate the engine? So, if the valves are seeming closed tightly, are they all like that because the lifters have no oil pressure behind them so they are bleeding down just enough to let them close?

So yea, the valves may be open, but not far enough to allow piston carnage.

allmotor · 06-22-2006, 09:46 AM

2.2 is a clearance engine (except mine w/ .600" list and 14½:1 compression. however, the "relax" position you mention still has several valves OPEN!!!!! even with no oil pressure to the LASH ADJUSTERS (these engines do NOT have lifters), there will be at least 3 valves open. It only takes one cylinder in compression to make the engine hard to turn over by hand.

why the hell would you pull the belt to look at the water pump on a 2.2/2.5. and if talking about a 3.0, if you pulled the belt to look at the water pump, you would replace it any way just as a maint necessity

phantomrt · 06-22-2006, 08:40 PM

I'll have to take a closer look next time I have a head off. The valves must not be open very far at all.

I had to remove the water pump to verify that I had the appropriate impeller on there and not a reman mistake. Its correct BTW. Removing the pump takes a fair amount of work to do. You can do it by removing the A/C compressor, A/C bracket, alternator, engine mount??, and the entire water pump housing from the engine, but there is an easier way that only requires scooting the intermediate shaft sprocket off a little way. I was a bit careless and accidentally pulled the sprocket off all the way. It took all of 5 minutes to re-time it.
Wait! Doesn't that sprocket hit the A/C bracket??? Yea, it used to.... I love my Dremel.

Some people call them freeze plugs. Freezing has nothing to do with their purpose. They are casting plugs but we all know what we're talking about. Sorry. LASH ADJUSTERS sergeant.

phantomrt · 10:11 PM

Quote:

Originally Posted by allmotor

there is NO such cam on a multicylinder engine, where ALL the valves are closed. there are positions where none of the valves are open far enough for the valves to hit... however several are still open some amount.

If you don't believe me, just pull the valve cover on your turbo dodge. you will see, no matter what postition you put the cam, there will ALWAYS be some valves open (even slightly)

Well, I did just as you said, plus more. This is what I found. Its hard to make sure I didn't cheat and remove the cam or the rockers or whatever you call them, but I assure the cam is there (you can see the cam gear) , the rockers are all in place (you can see half the rockers), the lash adjusters are in there.... anything else I'm missing? Multicylinder engine with all valves closed. The bowls are filled with water (why its darker) No, its not draining out. I can rotate the cam at least 4 degrees before feeling any kind of resistance also.

6G72 Cylinder head

Complete head. The recycling guy is gonna take it away for me. I have no use for it. Note water sealing in the bowls.

Underside of the head. This has probably NEVER been apart ever.

Just another pic.

Add another cylinder to the equation, and it could be a different story. Belt snaps, this is the cam/valve position that it will most likely stop in, and in a very short amount of time. Not a lot of rotating mass at half the speed of the crankshaft. I spun it up with my 3/8" drill and took the drill off the cam bolt, and yea, it stops quite suddenly.

Pretty sure my 24v 2.7L V-6 was the exact same way.