Valves squashed during installation

The car is a volvo 960 straight 6 aluminum engine

Maybe there is something here that may be useful http://www.volvoclub.org.uk/faq/EngineSealsBeltsVent.html#960TimingBeltChange

Two valid points. The timing belt broke and I was towed in to the nearest garage. The guy who repaired managed to assemble and squashed 2 exaust valves. Not sure how he did that.

I want to do myself now, but am trying to figure out how he broke the valves. Thought maybe the crankshaft pulley was 90 degrees out.

http://www.volvoclub.org.uk/faq/960_90Info.html#960B6304CamGearTiming

"I took a look at the 960 again last night and I came up with a way to solve the problem. The problem was that I took the cam gear off of the camshaft and did not know that it was not pinned or marked. This meant that it could go on the camshaft one of 3 ways at 120 degrees out of phase. With the intake manifold and exhaust manifold off I could see the valves. Had to use a mirror for the exhaust side. The spark plugs were out also. I set the timing marks and hoped for the best with a 1 in 3 chance of getting it right. I did not get any interference when I slowly turned the crank by hand, so feel will not work. I checked the firing order and compared the exhaust valves openings to the intake. Used a flashlight to shine in the plug holes and look in the ports to see when the valves would open. I found that the cam gear was off, making the intake and exhaust valves open and close at the same time. This is why there was no interference. So the intake valves were opening to soon. So I went back 120 degrees to the next hole and retested. This time the timing was correct. I then marked the cam gear to the camshaft so I would not have this problem again. So all you 960 owners out there be careful with the cam gears".

You'll need to investigate the opening and closing of your valves ...unfortunately this requires that you have knowledge of the valve opening and closing sequence of an infernal combustion engine.

http://www.animatedengines.com/otto.shtml

Note the matching of valve opening and closing sequence with the pistons position.

Regards Woody

Then my recent off topic comment was nearer than I thought!!!

It goes to show, always examine every part carefully when dismantling, just so's you know how to put it back together!

I use a center pop to mark each part in such cases.

In this case though, it was probably not needed to take that cam gear off at all......

Well done anyway.....

Here's my final offering for you.

http://www.brickboard.com/RWD/index.htm?id=1193002


Good luck.


Regards Woody

Hell, just stop the next guy who comes down the street and have him do the work. It couldn't be any worse than what you have already done and, who knows, he might get lucky.

Even a broken clock is right twice per day.

In the 4 cylinder BMW, the crank turns twice for EACH revolution of the camshaft.

This means that the timing marks can be aligned while the timing is 180 (crankshaft) degrees off.

The next but one rule is used when adjusting valve clearances (and setting timiing).

The firing order is 1-3-4-2. So that when adjusting valves on cylinder 1, cylinder 4 valves (next but one) are in the overlap position (both closed). If this cam was rotated 180 degrees, you would find that the crank had turned 360 degrees. If the timing mark were aligned on the camshaft, after this one-half revolution of the cam, the timing mark would now be off by 180 degrees. However, the crank mark would be in perfect alignment.

Here though we are dealing with a six cylinder engine. The next but one rule does not apply. Instead, use the next but two rule. So that if the firing order is 1-5-3-4-6-2, cylinder 4 would be on the overlap when cylinder 1 is at top dead center.

You had cylinder 6 at top dead center with cylinder 4 valves on the overlap. Valves 5, not 4 should have been in the overlap position. Thus the timing was off by 120 degrees. Valves got bent.

TDC_______ Next But 2

1_________ 4

5_________ 6

3_________ 2

4_________ 1

6_________ 5

2_________ 3

The chart shows the story. I have been there and done that.

"In the 4 cylinder BMW, the crank turns twice for EACH revolution of the camshaft."

True for any conventional 4 stroke piston engine

I would be more inclined to think that the valves were damaged when your timing belt broke rather than at re-assembly . How sure are you that the valves were not already bent or squashed ?

You can also easily time the cam by placing #1 cylinder at TDC then setting the cam so that the intake valve lobe at the #1 cylinder is in position to open the valve when rotation begins , the valve should begin to open as soon as the piston starts going down . ( then mount your timing gear on the cam ) Unless you have some wrong parts , everything should fall into place from there .

Would you like to rethink your last post? I think you will find the exhaust valve is next to open, after the power stroke.

But then I'm in the Southern Hemisphere,maybe its different in the North.

"You can also easily time the cam by placing #1 cylinder at TDC then setting the cam so that the intake valve lobe at the #1 cylinder is in position to open the valve when rotation begins , the valve should begin to open as soon as the piston starts going down . ( then mount your timing gear on the cam ) Unless you have some wrong parts , everything should fall into place from there ."

That's a fine way to set the companion cylinder to #1 near its TDC power stroke. It would be much easier to read and understand proper service procedure for the specific car than to rely on gimmicks that aren't precice or specific to the engine being worked on.

Your way would work mechanically (assuming that eyeballing the intake opening point even yielded exact #4 TDC position) because as default #1 would then also line up with TDC crank when the crank was turned 360 degrees. The problem is that you say to put the cam gear back on once you've "found #1 TDC on the cam". The cam gear has marks that professionals use to correctly time the engine, which would be 180 cam degrees off. Further, if this enngine is like a lot of modern OHC engines, it may have a cam sensor reluctor built in. You have no idea how messed up that situation could get if you tried to start an engine with the CMP exactly 180 cam degrees out of time.

Sincerely,

Other Guest

Note:

Timing marks on the crank/cam gears are not always accurate. Most of the time they are, but not always.

If you want to do this yourself, you need a GOOD service manual, or a printout of the repair information from a professional auto repair software program.

Preferably with photos and/or graphs of the various parts, including the cams/crank and their gears, with the timing marks indicated.

You should carefully compare the marks on your parts to those in the photos or drawings, and note their orientation to the cams and crank.

Also note is is possible to get the cams and crank out of phase as you assemble the engine. It is possible that as you install and tighten the belt, the cams and crank can be rotated slightly out of phase. It is often necessary to "fudge" the installation of the belt so that as it is tensioned into place, the tensioning "pulls" everything into the right phasing.

As you've seen, it is easy to destroy stuff if there is the slightest mistake.

Also note that some manufacturers use special indexing tools to orient everything as it is assembled. I don't know about your Volvo, but a large number of engines do.

If you're determined to do this, assemble it VERY slowly and immediately stop if you run into significant resistance as you turn the engine over. And, always turn it over manually before you try to start it.

An excellent and valid post. May I add to your last line which was:-

If you're determined to do this, assemble it VERY slowly and immediately stop if you run into significant resistance as you turn the engine over. And, always turn it over manually before you try to start it.

Then using a plastic rod, find the TDC of cylinder 1 and make sure that both valves are closed eg. not depressed. Also check that the rotor is now close to the wire for cylinder 1 spark plug (assuming conventional distributor!).

Then check the next cylinder by turning the engine in a clockwise direction (do any car engines turn anticlockwise?) about 180° (for a 4 cylinder engine, less or more for others....) and make sure that this also has both valves closed and that the rotor is now close to the wire contact for that cylinder.

Check the rest of the cylinders in the same way.

I then spin the engine over on the starter with plugs removed to get the oil pumped around to all bearings etc..... Its probably over doing it a bit.

Fit plugs and start engine.

Finely adjust engine timing using a strobe or computer, depending upon engine type and age....using/following the info from car engine manual.....

Volvo's cam timing do NOT get set when ANY piston is at TDC. If you set the pistons at TDC and put everything together, valves WILL bend.

You need to use the correct mark, which is usually about 30 deg. off of TDC. Its more of a 'theretical' position in which Volvo uses when setting up cam timing.

Sounds like the tech working on it made a mistake when setting it up.

THIS IS AN INTERFERENCE MOTOR. THE VALVE GOT BENT WHEN THE BELT BROKE. VALVE GOT COUGHT IN MECHANICS TRAP.

GOOD LUCK