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Valves squashed during installation

11/11/2009 10:44 PM

Hello Gentlemen

The guy in the garage located the timing belt in accordance to the 3 timing marks. Then tightened the top cover down onto the camshaft, squashing the exaust valves on cylinder 6.

When the timing marks are lined up, pistons 1 and 6 are at top dead centre.

I replced the damaged valves and now neither him nor I are inclined to do it again.

I had the idea that all the pistons should be in the mid bore position when the camshaft is placed, such that the valves are not pressed onto the camshaft.

My question is Are the timing marks correct (ie piston at top dead centre) or has the crankshaft pulley been moved.

Is it normal to tighten the camshaft pulley down onto the valves and press them open. (In our case they were pressed onto the piston at TDC)

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#1

Re: Valves squashed during installation

11/11/2009 10:50 PM

The car is a volvo 960 straight 6 aluminum engine

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#2
In reply to #1

Re: Valves squashed during installation

11/12/2009 1:22 AM
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#3

Re: Valves squashed during installation

11/12/2009 10:33 AM

Planet of the Apes

It would help if you didn't keep flitting around starting new threads!

http://cr4.globalspec.com/thread/45901/Valve-Timing-Volvo-960

http://cr4.globalspec.com/thread/45800

http://cr4.globalspec.com/thread/45648

http://cr4.globalspec.com/thread/45645

These threads ...IMO.. seem to boil down to this ...you and the mechanic haven't got much of a clue about the Volvo engine and should either give up or pay a professional to sort out the mess that you appear have got yourself into.


Regards Woody

http://cr4.globalspec.com/search/sitesearch?do=show&us=15327&srchobjs=t,be

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#4
In reply to #3

Re: Valves squashed during installation

11/12/2009 8:18 PM

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.

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#10
In reply to #4

Re: Valves squashed during installation

11/13/2009 7:53 AM

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

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#12
In reply to #10

Re: Valves squashed during installation

11/13/2009 8:05 AM

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.....

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#13
In reply to #10

Re: Valves squashed during installation

11/13/2009 8:31 AM

Here's my final offering for you.

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


Good luck.


Regards Woody

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#5

Re: Valves squashed during installation

11/12/2009 10:30 PM

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.

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#14
In reply to #5

Re: Valves squashed during installation

11/13/2009 10:21 AM

Even a broken clock is right twice per day.

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#6

Re: Valves squashed during installation

11/13/2009 12:30 AM

Well Planet of the Apes, it can be normal for 1 and 6 to be at TDC when the motor goes back together. As for how two exhaust valves were bent, let me state the obvious. The engine wasn't timed correctly. I, in my amazing brilliance did manage a similar feat on the first BMW 4 cyl engine I rebuilt. The timing marks didin't line up the way I thought they did according to the directions given.

I have two bits of advice to help prevent such a situation from arising again. The very first thing you do is revert to the printed word. For the cost of two valves you should be able to buy a Clymer or Haynes manual for your car (and engine). Read it several times to make sure that you fully understand what and where the marks are to be. Keep the book on the fender ( or front wing if you are a Brit) and refer back to it if you have the least iota of doubt and keep doing so.

The next suggestion is a bit more problematic. Double check by taking a look at where the cam lobes are when you think you have it timed correctly. If one of the lobes has a valve opened on a cylinder that you know has a pistion at TDC, you don't have the timing right. If this happens, go back to step one---read the book again. Under no circumstances do you rotate the cam more than a few degrees with head bolted in place. If you do, you run the risk of bending valves if you try to force the cam to rotate.

When you get to the point where everything seems right and you hae it bolted down and the belt on, rotate the motor gently by hand to check to make sure that there isn't a piston to valve conflict on any cylinder. If there is, the motor will stop and turning it by hand will be slow enough to not do any damage. If this does happen, go back to step one.

There is nothing more satisfying than working through a problem and getting it back together right. But, it may take a bit of time to sort through.

Next time replace the cambelt in accordance with the mfg spec or even earlier. Its much more relaxing to do the work on your terms rather than a "must do" job.

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#15
In reply to #6

Re: Valves squashed during installation

11/13/2009 11:00 AM

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.

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#18
In reply to #15

Re: Valves squashed during installation

11/14/2009 1:25 AM

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

True for any conventional 4 stroke piston engine

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#7

Re: Valves squashed during installation

11/13/2009 3:14 AM

It probably has little to do with your problem bit I had a colleague, many years ago now, who rebuilt his 1.6 liter Ford Capri motor and could not get to start, it just sort of "Farted around" so to say, but not run.

After 3 days he asked if I could take a look and of course I did.

What I found out was that he had done a good job but the camshaft was timed differently to the original (I still haven't a clue as to why). His old one fired 1,3,4,2 and the new one was 1,2,4,3.

I swapped the plug leads around to suit the new cam and the engine started and ran immediately, just like it should do.

That is the only time in my life that I have seen an engine run in 1.2.4.3 mode.....

It would appear that Ford sold both types of cam for the engine and the mechanic sorted out the wrong fiche page to order from.

At the end of the day, we had to by a few feet of ignition cable to get to the spark plugs from the distributir in a better less tight manner than my "Quick-Fix", but that was all......

Marked as off topic as it probably is!!

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#8
In reply to #7

Re: Valves squashed during installation

11/13/2009 6:48 AM

Andy,

amazing! I have never heard of that before!

But then I am not a car mechanic, I only do cars when I really, really have to, the last time was just over 20 years ago when I helped my son in-law strip my daughters car's engine, down to the cylinder head and build it back again.

As per many posts - we made sure that we had the manual b4 we started.

Your experience was not what I would have expected - it's why you buy the manuals!

Right?

Sleepy

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#11
In reply to #8

Re: Valves squashed during installation

11/13/2009 7:53 AM

In the case I mentioned, my cooleague had the Haynes manual, but no mention was made of a "reversed" cam. I just turned the engine over slowly and watched the position of the rotor arm.

Not difficult for a logical person like me......I mean that quite sincerely, logic was and is still my forte!! My wife hates my logic by the way!!

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#9
In reply to #7

Re: Valves squashed during installation

11/13/2009 7:14 AM

I helped a friend with the cam in a ford 289. We put everything back together and it was like the engine was trying to burn down the garage we were in. After trying half a dozen firing orders he sarcasticly asked for any firing order other than a 289 or 302. Turned out a cam from a 351 windsor fit, and that firing order made it purr.

Not a ford fan.

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#17
In reply to #9

Re: Valves squashed during installation

11/14/2009 12:58 AM

I have a 351W I built in 1995 that has a 302 non HO cam in it which required changing the ignition firing order, just a simple detail, but important for those engines.

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#16

Re: Valves squashed during installation

11/13/2009 11:09 AM

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 .

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#20
In reply to #16

Re: Valves squashed during installation

11/14/2009 1:50 AM

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.

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Anonymous Poster
#22
In reply to #16

Re: Valves squashed during installation

11/16/2009 11:06 AM

"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,

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#19

Re: Valves squashed during installation

11/14/2009 1:39 AM

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.

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#21
In reply to #19

Re: Valves squashed during installation

11/14/2009 4:26 AM

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.....

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#23
In reply to #21

Re: Valves squashed during installation

11/16/2009 11:55 AM

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.

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#24

Re: Valves squashed during installation

03/16/2010 10:41 AM

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

GOOD LUCK

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