Odd Ball - Cam Fail?

new 6/01/2004

The owner had ticking and then while cruising on the freeway lost power. Pulled off at the next exit and had it towed home. He stripped the cam covers and in doing so found that number 8's COP looked like it had been burnt. Well that and some arcing which had eroded the screw top of the plug. The lower half of the COP was broken off completely. He had changed his plugs around 100K and car now has 117K.

I couldn't see any damage at any of the sprockets, feel any play and hear/feel any contact when the engine was rotated so went ahead and welded the cams as an additional check we ran a compression test and I'm trying to understand the results. 1,2,3 and 4 seemed to be giving 60 PSI, 5,6,7 gave 150,170, 150 PSI, No. 8 we couldn't get the tester to thread in - no value.

My thinking goes that if the highway failure had caused a valve crash it shouldn't get any compression values at all on 1-4 - got 60 PSI but only 60.

I think No. 8 may have been crossed and the COP destruction was caused by blow-past. He's going to try to clean out the threads and try the test again.

I've suggested he check the timing on the cams. Anyone know an easy way without the cam locking brackets? If not it would appear that the flatratetech CD has the detailed values if not.

Any thoughts?

jj

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jj-
the 60# s on the 1-4 cyl has me more concerned than the #8 plug threads. Kirk once spoke of a MAIN timing chain sprocket letting go - keyway and all. If you say there is NO EVIDENCE of sprocket movement on the cams themselves (won't move NOW, you welded them) then the next place to check is to compare one head to the other for being parallel to one another.
The cams have a large piece with flats on the passengers end which locks into the cam locating/timing brackets you mentioned. With all the timing marks in place, the flats on those pieces should be PERPENDICULAR to their respective heads-
i.e. - equals sign is the flats. "l" is the head face.

l= is correct
_= is incorrect

You should be able to get a good idea of angle from head to head with a small 90' square tool of some kind.
If the MAIN sprocket on one head or the other has slipped and cut the keyway you will have one set of cams IN TIME, flats perpendicular to the head face, and one set of cams OUT OF TIME, say 45' to the head face. It WONT be too close to tell if you slipped enough to damage the head.
Uncommon problem to say the least. If this is your problem I would expect 16 valves damaged on that head.

Regards
Eric Lehmann
97 Ebony - welded
97 Toreador Red # 285 - welded
96 Willow Green # 326 - FUBAR MOTOR (give me a few weeks)
91 Jade Plus SHO-fa

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Checking the valve lash will give you a good idea if there is valve damage...

Scott

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Yep. That's what I got from the CD. Thanks for confirming Eric.

I've been trying to get my hands on a failed unit to rebuild but no luck yet. One went on ebay a couple of days ago for $455.

I'd settle for one in a car local, low mileage, at the right price.

jj

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I have a set of heads that need rebuilding. Nothing bent just a bit rusty. After talking to one of the ROTBs participants I am considering an upgrade to the 3.0L Duratec valves. Any thoughts?

Paul Nimz

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I had a fellow bring me 3 old cams and a new cam in a box for welding. His camfailure broke a couple of valves and trashed a cylinder head. He showed me the repaired head with New guides, etc. (The whole 9 yards) But what blew me away was the faithful reproduction of the combustion chamber, remachining and reinstallation of the valve seats where only shattered metal fragments had been.
He got away for a song too, IIRC.
http://cylinderheads.com

Eric

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