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  #1  
Old 12-23-2001, 08:10 PM
Swinger321 Swinger321 is offline
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Angry OWWMIGOD!!! Cam Thrust Plate broke in 3 places!!!!!

Well I just pulled the 318 ouuta the dart and began tearing it down so I could assess the damage to the #2 piston after I didn't match the valvesprings to the cam. I was pulling the pan when I noticed a small bolt in the pan. Hmmm thought at first it was a torque convertor bolt by its weird head. The it struck me.....it was a cam thrust plate bolt. So I pulled the front timing cover to find the Cam Thrust Plate broke in 3 places!!!


First off......what caused this?
Did I not torque the bolts good enough?
Do New Cams require a new torque setting?


Secondly....what Can I do to prevent this from happening again?

And lastly....One bolt has a small chew mark on it, should I check it for jumping time also?

Out of 8 pistons, it only got one so " I " think it didn't jump time and COIL BIND was my culprit.

But let me know what you all think....I trust you guys' advice.

Thanks,

Swinger321
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  #2  
Old 12-23-2001, 10:01 PM
jelsr jelsr is offline
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I'm a little confused here, when you say it got 1 piston are you talking piston-valve contact? When you get into coil bind it usually gets pushrods or rockers. Since the plate is broken you should make sure the cam didn't move out of line enough for the lobes to contact an adjacent lifter, that will ruin a cam quickly. The lifter face is slightly convex and the cam lobes are tapered to match and run against the lifter off center. This causes the lifter to rotate and also provides some thrust against the plate. Loctite does wonders for bolts that live in dangerous territorys.
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Old 12-23-2001, 11:41 PM
Swinger321 Swinger321 is offline
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Biggrin Lifters Rotate.....huh?

I know for a fact my lifters don't rotate. At least not the body of the lifter.....maybe the roller tip,,, I HOPE it rotates and thanks for the tip on loctite. I SHOULD have used that before but the engine never had a problem before the new cam, so I figured what tha' H***. Thanks again for the reply.

Swinger
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Old 12-24-2001, 02:40 PM
jelsr jelsr is offline
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If you have a roller setup you're right, they do not rotate. I just assumed it was a flat tappet cam. When the spring coil binds the valve cannot move any further and the pushrod usually bends but possibly the rocker. Did you have any bent pushrods? Also I am still at a loss on the piston problem. Was this due to piston/valve contact? A valve can gall and stick in the open position for a fraction of a second and you have problems. The valve stem bends and cannot close which further aggravates the problem. Rule of thumb on misc. bolts in hostile environments (cam plate, oil pump mounting, etc) safety wire or loctite.
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  #5  
Old 12-24-2001, 05:48 PM
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rumblefish360 rumblefish360 is offline
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Since you had a piston to valve collision, I would check it all out. Start with cam inspection, tappets and there parts, roller ockers(?) and there parts, roll the pushrods on a table then check the cams timing. Or retime when you reinstall the cam from inspection. Check the chain and gear as well. There could be some gauling.
Check the valve that hit the head, It still may be good.
Torque to spec with clear clean threads and a quick coat of the locktight and that should be it.

Good luck.
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  #6  
Old 12-24-2001, 07:56 PM
Swinger321 Swinger321 is offline
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Smile Thank you all.

Thanks for all the recommendations. I will use loctite when I reassmeble. Yes I had piston to valve problems and I believe the valve stuck down and the piston hit it once and bent it then proceeded to beat the crap outta it on my short drive home. Bent the valve in a "S" shape, valve looked bad. It was only obvious when I pulled the valve cover and saw the #2 cylinders exhaust valve sticking up 3/4" mor than the others. I thank you for your advice.

Swinger321
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  #7  
Old 12-25-2001, 01:22 PM
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rumblefish360 rumblefish360 is offline
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YIKES Good luck.
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  #8  
Old 12-25-2001, 01:46 PM
PRO PRO is offline
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I think something else happened,1st to break a cam retaining plate is a very unusual prob,it helps to keep the cam from walking forward right out of the block,the dist drive gear and oil pump drive keep it from walking out the back of the block,I would look there for the source of your prob,the valve hitting the piston is most likely a result of the lifter(not rocker arm)walking off the cam lobe as the cam moved forward and broke the retaining plate,it may have rode on the adjacent cam lobe which will cause it to hit the piston,definately remove the cam and inspect it thoroughly as well as the bottom of the lifters,inspect the dist drive gear teeth for rounded or missing teeth,look at the bushing thats pressed into the block in which the dist shaft rides it may be worn oversize or elongated,from what you said earlier that your lifters dont rotate but the tips do,did you mean your roller tipped rocker arms?,their in the head,lifters ride directly on the cam(they rotate)??????????? anyhow be very thorough in your exam so that it doesnt go back together and have more probs,hope this helps........PRO.....
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  #9  
Old 12-25-2001, 02:26 PM
jelsr jelsr is offline
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I agree with Pro, something still smells funny. You said the ex on #2 was sticking up above the rest. That indicates the valve is in two pieces if you can still see stem protruding from the retainer. If it separated that would explain the contact, probably several times in rapid succession! Not to make light of your problem! Our intention is to help make sure it doesn't happen to you again. Roller cams have no thrust to hold them against a thrust plate so other means are necessary, buttons for example. If the cam moved far enough for the rollers to drop off the side of the lobes you would have more than a small bolt in the pan. Really lay the eyeball on all the parts involved, because nothing explains the broken plate.
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